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tetrapodzoology
Feathers and filaments of dinosaurs, part II
By tetrapodzoology on March 2, 2007.
In the previous post we looked at the feathers and filament-like structures that covered the bodies of coelurosaurian theropods. While basal coelurosaurs - compsognathids and tyrannosauroids - possessed filament-like 'Stage 1' structures alone, members of Maniraptora (the coelurosaur clade that includes oviraptorosaurs, therizinosauroids, birds, deinonychosaurs and, probably, alvarezsaurids) possessed indisputable vaned feathers. That is, complex feathers that had a distinct central rachis with vanes on either side composed of parallel barbs. What is surprising is how luxuriant some of this covering seems to have been, and on how much information we now have about the arrangement of feathers on the bodies of these dinosaurs...
Though it has been suggested at times that vaned feathers simply must have evolved for flight, the phylogenetic distribution of these structures currently indicates that they first evolved in flightless maniraptorans and were only later exapted by long-armed maniraptorans for use in locomotion. Of course a well-known minority opinion, best known from the writings of Greg Paul, is that feathered maniraptorans are secondarily flightless and descend from volant bird-like ancestors. While this remains possible it lacks support from the fossil record, though that may or may not mean much. I want to avoid discussion of this area here and will cover it another time [image of sinornithosaur above borrowed from here].
Feathered fingers and hand flags
Exactly how feathers were arranged on the arms and hands of both basal birds and non-avian maniraptorans has long been unclear, and both non-avian maniraptorans and archaeopterygids have conventionally been depicted as possessing unfeathered fingers. However, this just doesn't work given that the second finger is needed to support the remiges* that we now know were present throughout maniraptorans: this is what it does in living birds. Derek Yalden's 1985 study was important in showing exactly how the remiges would have grown off of the first and second phalanges of the archaeopterygid second finger (Yalden 1985) [adjacent image shows Yalden's reconstruction of Archaeopteryx, with a modern magpie's wing above it]. A check of the literature on archaeopterygids shows that this configuration has been widely recognised (Bohlin 1947, Rietschel 1985, Griffiths 1993, Stephan 1994, Elzanowski 2002), though rarely brought to the attention of artists for some reason.
* Remiges are the large feathers of the forelimbs (singular remex). The large feathers that grow from the tail are termed rectrices (singular rectrix).
Incidentally, there has been some minor historical disagreement over exactly how many remiges were present in archaeopterygids (there were most likely 11 primaries and a tiny distal 12th one, and at least 12 secondaries), and also about how the hand claws were arranged: I agree with Elzanowski (2002) that the claws were directed perpendicularly to the palmar surface in life, and rotated anteriorly in most (but not all) specimens during burial. It has also been suggested on occasion that the fingers of archaeopterygids and other feathered maniraptorans were united in a single fleshy 'mitten' as they are in modern birds, and hence unable to be employed in grasping (Martin & Lim 2005). Given that the interphalangeal finger joints of archaeopterygids appear suited for flexion and extension, and that the third finger apparently remained free and flexible in birds more derived than archaeopterygids (Gishlick 2001), this is unlikely to be correct; it's based on a depression in the sediment that Martin and Lim identified around the bones.
[Image above of excellent Caudipteryx skeleton from here].
Like those of archaeopterygids and modern birds, the remiges of non-avian theropods would also have been attached to the phalanges of the second manual digit as well as to the metacarpus and ulna, and indeed we can see this in the fossils. It's the case in the sinornithosaur NGMC 91-A and Microraptor (remember that, while we now have more feathered theropods that we did just a few years ago, we still only have soft-tissue preservation in a tiny minority of taxa). Surprisingly, in Caudipteryx the remiges are restricted to the hands alone, and don't extend from the arm [see image below]. They seem to have formed little 'hand flags' that are unlikely to have served any function other than display. Were 'hand flags' unique to Caudipteryx, or more widespread? Were all oviraptorosaurs like this?
If you're wondering: yes, Caudipteryx (currently represented by two species, C. zoui Ji et al., 1998 and C. dongi Zhou & Wang, 2000) is an oviraptorosaur and possesses a suite of characters unique to this group. It is not a member of Aves, despite the efforts of some workers to make it into one. In contrast to later members of Oviraptorosauria, it possessed premaxillary teeth, had proportionally elongate hindlimbs and lacked a claw on its third manual digit. For a previous post on oviraptorosaurs see Luis Rey and the new oviraptorosaur panoply, and for a discussion of tooth function in Caudipteryx and other feathered maniraptorans see The war on parasites: an oviraptorosaur's eye view.
Given that several maniraptoran lineages were clearly predatory and, given the morphology of their manual claws, fingers and wrists, presumably in the habit of grabbing at prey with their hands, wouldn't the remiges have interfered with the use of the hands in predation? The short answer is no. The long answer - taken here from a paper Alan Gishlick published on forelimb function in Deinonychus - is 'feathers on the hands would not have greatly impeded the use of the hands in predation. Because the feathers are attached at an angle roughly perpendicular to the claws, they are oriented tangentially to the prey's body, regardless of prey size' (Gishlick 2001, p. 315). It is important to note here that theropod hands appear to have been oriented such that the palms faced medially: that is, they faced inwards, and were not parallel to the ground as used to be imagined [adjacent image of Microraptor wing from here].
However, feathering would have interfered with the ability of the hands to bring a grasped object up toward the mouth given that extension of the maniraptoran wrist would have caused the hand to rotate slightly upwards on its palmar side. If both feathered hands are rotated upwards and inwards at the same time, the remiges from one hand would collide with those of the other. For this reason, maniraptorans with feathered hands could grasp objects, but would probably not be able to carry them with both hands. Senter (2006) has proposed that dromaeosaurids and other maniraptorans may have solved this problem by clutching objects single-handedly to the chest. Feathered hands would also have restricted the ability of the hands to pick objects off of the ground, given that the feathers extend well beyond the ends of the digits.
It remains possible that some maniraptorans lacked remiges on their fingers, but the only evidence we have in fact indicates the contrary. It's recently been argued that the particularly long second digit of the oviraptorosaur Chirostenotes was used as a probing tool, locating and extracting invertebrates and small mammals and so on from crevices and burrows (I have a post planned on this subject - it's to be called 'The probing guild' - and will talk more about this subject then). It seems highly unlikely that a digit that is regularly thrust into small cavities would have had feathers extending along its length, so either Chirostenotes didn't probe as proposed, or its second finger was unfeathered, unlike that of Caudipteryx and the other feathered maniraptorans [adjacent Microraptor image from here].
Given the problems that the feathers might have posed for clutching and grabbing prey from the ground, we might also speculate that some of these dinosaurs deliberately removed their own remiges by biting them off. Some modern birds (notably motmots) manipulate their own feathers by biting off some of the barbs, so this is at least conceivable, albeit totally speculative of course.
I wanted to cover hindlimb and tail feathers too, but... another time. Come back soon!
Refs - -
Bohlin, B. 1947. The wing of Archaeornithes. Zoologiska Bidrag 25, 328-334.
Elzanowski, A. 2002. Archaeopterygidae (Upper Jurassic of Germany). In Chiappe, L. M. & Witmer, L. M. (eds) Mesozoic Birds: Above the Heads of Dinosaurs. University of California Press (Berkeley), pp. 129-159.
Gishlick, A. D. 2001. The function of the manus and forelimb of Deinonychus antirrhopus and its importance for the origin of avian flight. In Gauthier, J. & Gall, L. F. (eds) New Perspectives on the Origin and Early Evolution of Birds: Proceedings of the International Symposium in Honor of John H. Ostrom. Peabody Museum of Natural History, Yale University (New Haven), pp. 301-318.
Griffiths, P. J. 1993. The claws and digits of Archaeopteryx lithographica. Geobios 16, 101-106.
Martin, L. D. & Lim, J.-D. 2002. Soft body impression of the hand in Archaeopteryx. Current Science 89, 1089-1090.
Rietschel, S. 1985. Feathers and wings of Archaeopteryx, and the question of her flight ability. In Hecht, M. K., Ostrom, J. H., Viohl, G. & Wellnhofer, P. (eds) The Beginnings of Birds - Proceedings of the International Archaeopteryx Conference, Eichstatt 1984, pp. 251-265.
Senter, P. 2006. Comparison of forelimb function between Deinonychus and Bambiraptor (Theropoda: Dromaeosauridae). Journal of Vertebrate Paleontology 26, 897-906.
Stephan, B. 1994. The orientation of digital claws in birds. Journal fur Ornithologie 135, 1-16.
Yalden, D. W. 1985. Forelimb function in Archaeopteryx. In Hecht, M. K., Ostrom, J. H., Viohl, G. & Wellnhofer, P. (eds) The Beginnings of Birds - Proceedings of the International Archaeopteryx Conference, Eichstatt 1984, pp. 91-97.
Mesozoic dinosaurs
I thought NGMC-91 lacked primary feathers, or at least had none preserved. I admit it would be odd for a maniraptoran...
By Mickey Mortimer (not verified) on 02 Mar 2007 #permalink
Interesting work, thanks Darren. Has it been determined whether the first feathered therapods had a bipedal hopping gait or bipedal walking gait or some other gait?
Would they have been able to climb-hop steep inclines or near vertical cliffs, perhaps flapping to gain lift, and then gliding down after? This would allow safe nesting from egg eating nocturnal mammals and diurnal snakes, and would have selected for ovoid or oblong eggs, as opposed to the primitive spherical egg shapes of sauropods and sea turtles. I think this was critically important during the KT extinction, at least as significant as any impact or vulcanism event. I did a search here for "egg" but got no results, have you written anything on therapod or bird eggs? I'm wondering if there are distinct correlations between the earliest flight feathers and the resulting shape of eggs.
DDeden (David Deden)
By DDeden (not verified) on 02 Mar 2007 #permalink
Hey TZers,
If you want to read the carefully reasoned, fully documented, phylogenetically, anatomically, and taphonomically informed tower of blinding excellence that is Martin & Lim 2005, you may do so for free here.
Don't be put off by the challenging length of this abstra--uh, paper. About half of its hefty 1.3 pages is taken up by detailed scaled figures that confirm the authors' interpretation beyond all possible doubt. You'll still have to slog through 373 words of text to get all the meaty science, though. If my tone comes across as facetious, perhaps it's because I've written longer figure captions.
By Dr Vector (not verified) on 02 Mar 2007 #permalink
Kinda random, but I just finished a gallery of Dinosauroid cave art, of a kind I think you'll enjoy greatly.
http://www.nemoramjet.com/dinoindex.html
By nemo ramjet (not verified) on 03 Mar 2007 #permalink
Matt: "I've written longer figure captions" is one of the best scientific smackdowns I have heard in ages!!
Mickey: Although "Dave" doesn't clearly show primary feathers, there are "ghosted" regions of herringbone patterning on the slab that **might** be traces of these. Part of the problem of the variable preservation of integument, even under the best of conditions.
By Thomas R. Holtz, Jr. (not verified) on 03 Mar 2007 #permalink
how the remiges would have grown off of the first, second and third phalanges of the archaeopterygid second finger
Er, no, just the first two phalanges. The third is the claw, and does not bear a feather in the reconstruction. :-]
Surprisingly, in Caudipteryx the remiges are restricted to the hands alone, and don't extend from the arm
They can't maybe be stuck in the counterslab, the fossil having split above the gastroliths...? Note how it is split through one of the forearm bones.
About the eggs: IIRC all known Mesozoic theropod eggs are egg-shaped rather than spherical, but so are crocodile eggs, for example. Cliffs are not always easy to find; there don't seem to have been any in the Yixian Formation environment, for example.
By David Marjanović (not verified) on 03 Mar 2007 #permalink
About half of its hefty 1.3 pages is taken up by detailed scaled figures that confirm the authors' interpretation beyond all possible doubt.
GAH! That photo is among the worst examples of JPEG compression I've ever seen. It shows nothing. Does it look better on paper...?
Couldn't the hand feathers have been used as part of the grip, for example forming a bowl or scoop to collect small prey?
By David Harmon (not verified) on 03 Mar 2007 #permalink
'Does it look better on paper...?'
Another desperate effort to make archaeopterygids (and other Mesozoic maniraptorans) more like modern birds than they apparently were.
By tetrapodzoology on 03 Mar 2007 #permalink
I admit to being a dino-ignoramous, a non-specialist naturalist. I do however think that my interpretation of egg shapes and their relationship to predation and habitat is correct.
The sauropodian sphere shaped eggs are most primitive and were laid on soft dry beach sand and covered with sand to be warmed by the sun, like sea turtles. Spherical eggs are the most efficient, and strongest, and space filling. Any other shape is inferior, and must have had strong selective pressure to be altered. Bird eggs are ovoid due to having had cliff-nesting ancestors, the common murre's strongly ovoid shape is a good indicator of the ancestral condition of all birds. While nocturnal mammals were busy consuming easily accessed sauropod eggs and other non-cliff nesting dinosaurian eggs, those species which laid their eggs on cliffs and off-shore isles were safely hatched.
Snakes were important diurnal burrowing predators of eggs, however they too laid eggs and so were vulnerable, some more recently became live-birth. Early mammals were omnivorous but specialized in nocturnal burrowing egg consumption, rather than burying their own eggs, they buried themselves and entered a form of torpor during the dry or cold season, (parallels to crocs and platypus) so the young were protected.
Theropod eggs were oblong, not ovoid, were laid dually, this indicates a departure from the primitive condition, which I think is due to hopping-flying-gliding habit, although I don't know the significance of the spiralled egg heap, which certainly does not fit with cliff nesting.
I agree with Martin & Lim that the hands were used for climbing and not for grasping prey. Rigid scales (like fingerprints) would perform better than loose feathers for gripping.
DDeden
I much preferred this post to the previous one. Very informative and I wasn't aware of most of that information. Terrible resources here in Alaska. One of the reasons I like this blog, in fact--I always learn something new.
By Halbred (not verified) on 04 Mar 2007 #permalink
Sorry, I meant ridged scales, rather than rigid scales, in the last sentence of my post.
Sorry for the size of this post.
The sauropodian sphere shaped eggs are most primitive and were laid on soft dry beach sand and covered with sand to be warmed by the sun, like sea turtles.
No, they were not covered with sand.
Luis M. Chiappe, Frankie Jackson, Rodolfo A. Coria & Lowell Dingus: Nesting titanosaurs from Auca Mahuevo and adjacent sites: understanding sauropod reproductive behavior and embryonic development, p. 285 -- 302 in Kristina A. Curry Rogers & Jeffrey A. Wilson (editors): The Sauropods. Evolution and Paleobiology, California University Press 2005
Spherical eggs are the most efficient, and strongest, and space filling. Any other shape is inferior, and must have had strong selective pressure to be altered.
Off the top of my head, I can suggest two:
- Not all fetuses can be curled up into a ball equally well.
- If the eggs get so large that the diameter of the oviduct and/or cloaca becomes limiting, an elongate shape can contain a larger volume than a sphere with the same diameter.
Bird eggs are ovoid due to having had cliff-nesting ancestors, the common murre's strongly ovoid shape is a good indicator of the ancestral condition of all birds.
But have a look at the position of the murres within the bird tree. There is no reason whatsoever to consider their extreme egg shape the ancestral one of all birds.
Is the shape of laevisoolithid eggs (ascribed to Enantiornithes) known?
While nocturnal mammals were busy consuming easily accessed sauropod eggs and other non-cliff nesting dinosaurian eggs, those species which laid their eggs on cliffs and off-shore isles were safely hatched.
Then why have the pterosaurs died out while the crocodiles have not? Let alone the turtles!
There is no known Mesozoic (...or later) mammal that was specialized for eating eggs. Importantly, most of them were too small to crack sauropod eggs (at least).
Most importantly, why should large numbers of mammals suddenly have switched to egg-eating 65.5 Ma ago? Mammals in the narrowest sense had been around since the Middle Jurassic at least, and mammals in a more common sense since the Late Triassic. Never forget that the Cretaceous alone was longer than the entire time that has passed since.
Surely you've heard of Repenomamus? That one was large enough to damage most or all eggs. And it lived in the middle of the Early Cretaceous.
Snakes were important diurnal burrowing predators of eggs,
Most of those eggs were too big for anything smaller than Dinilysia.
however they too laid eggs and so were vulnerable, some more recently became live-birth.
Having died out due to their eggs being eaten, they evolved live birth and then resurrected?
Of course not. Most snakes still lay eggs.
Early mammals were omnivorous
but specialized in nocturnal burrowing egg consumption
Then wouldn't they show at least one single adaptation to that? Because... they don't.
rather than burying their own eggs
Does the platypus count?
Theropod eggs were oblong, not ovoid, were laid dually, this indicates a departure from the primitive condition, which I think is due to hopping-flying-gliding habit
And what does the carnosaur Lourinhanosaurus have to do with hopping, flying, or gliding?
I agree with Martin & Lim that the hands were used for climbing
Then why don't the feet fit climbing any better?
and not for grasping prey. Rigid scales (like fingerprints) would perform better than loose feathers for gripping.
The feathers were on the other side of the fingers. We don't know what there was on the palmar side. And if that side was feathered, too, we still need to take the huge claws into account.
Judging from its skull, Confuciusornis was clearly not a carnivore, but with its 1st and 3rd fingers it was surely capable of grasping and holding anything it wanted, don't you think?
If the eggs aren't round then a spiral pattern is probably the easiest way for the mother to lay her eggs in terms of packing them into the nest. This pattern of egg-laying is (iirc) seen in Protoceratops and Oviraptor (I can't remember if all "Protoceratops" nests are now considered to be Oviraptor). Neither animal nested on cliffs. Oviraptor incubated its eggs like a bird, whereas Protoceratops may have buried them.
By Dave Godfrey (not verified) on 05 Mar 2007 #permalink
(I can't remember if all "Protoceratops" nests are now considered to be Oviraptor)
AFAIK all are now considered oviraptorids (all have the same eggshell type AFAIK).
I forgot to ask: owls have evolved spherical eggs (and nest in tree holes); why haven't more bird clades? Owls are neither particularly old nor particularly young.
Thanks for responding, I may be mistaken in some parts, I'm simply not sure, however I'll stand by this statement:
ALL extant Aves spp. derive from cliff nesting ancestors which survived a massive extermination by nocturnal egg eating mammals, indicated by widespread ovoid egg shape commonality (one possible exception, a New Guinea region bird which drops it's eggs in sun-warmed beach sand pockets).
I have no idea if this is a conventional or radical paleontological interpretation, only that it seems the most parsimonious to me.
Well, you haven't explained yet how you have reached this conclusion. The few points that you have made -- Mesozoic mammals having been specialized egg-eaters, for example, or the assumption that mammals somehow mattered at the end of the K but had not mattered for the rest of the Mesozoic -- are demonstrably wrong, as I have explained above. If the premises are wrong, why isn't the conclusion?
Briefly: ALL extant Aves spp. derive from cliff-nesting ancestors which survived a bottleneck, indicated by commonality of ovoid egg shape.
(Current aves with spherical or US football shaped eggs (emu) are derived from former ovoid eggs.)
An ovoid egg rolls in an arc, a spheroid eggs rolls in a straight line off a cliff. Under no other circumstance can I imagine ovoid eggs being so strongly selected for in nature, as they are of inefficient form, and must be rotated for the chick to survive, (unlike turtle eggs) which is hazardous on rocky cliffs.
Why are kiwi eggs so huge? Why not a bunch of hummingbird-egg sized eggs? Note the ovoid shape.
Diverticula (per Dr. Vector's paper, mentioned above) are for phonation, display; also for flotation (pharyngeal air sac in walrus inflated during sleep in water, likely also laryngeal air sacs in miocene apes, pliocene apiths).
Because of my relative ignorance of all things pre-pleistocene, I hesitate to try to explain in any sort of detail, being unfamiliar with the terminology.
However, the saber-toothed marsupial kangaroo & cat fossils found recently might provide a clue on how large eggs could have been consumed by early marsupial mammals. Both of these could likely dig into burrows, climb low-branched trees (parallel tree kangaroos, clouded leopards) and non-vertical cliffs, but not vertical cliffs nor offshore large-wave-ridden isles.
Early marsupial bipeds may have laid monotreme-like eggs held in a skin-fold (parallel to emperor penguin) during a period of torpor (in burrow or on tree branch), with early hatching offspring feeding off apocrine scent and oil glands in the skin fold, thus getting a head-start over later-hatching off-spring, the young being slightly parasitical (non-injuriously) on the mother.
With time and selection, the skin fold evolved into a pouch, and the egg shell reduced to a (after-birth?) membrane. Importantly, the young were no longer left immobile (parallel bird egg) but rather became mobile (parallel angiosperm seed) and well protected, which had a profound impact on the ecosystem, since the normal cycle of predation-on-young was circumvented.
Since sauropods fetuses can fit into a spheroid egg, I would think any other fetus would also.
"If the eggs get so large that the diameter of the oviduct and/or cloaca becomes limiting, an elongate shape can contain a larger volume than a sphere with the same diameter."
Elongated, yes, due to narrow hips (flight, snake-burrowing), however elongated eggs are in egg masses, not single-large eggs. Ovoid, no, a very different cause is required to produce large ovoid eggs.
"Murre's bird tree" relationship insignificant, Aves not derived from murres, parallel convergence of murre to ancient Aves bottleneck cliff-side condition.
Pterasaurs laid leathery eggs, not hard ovoid eggs, nest not known.
Crocs, turtles could swim to isles better than early mammals.
Conjecture: Lizards and snakes may have previously had hollow fangs used to puncture and siphon egg fluids (parallel mosquito), later saliva toxins or viral infections allowed more effective (less metabolically costly) predation upon other prey. Small eggs swallowed whole, large eggs punctured.
Snake eggs are leathery oblong, (not hard shelled spheroid or ovoid), laid in masses.
Early mammals were not omnivorous?
I think theropods were arboreal perching ground nesters, probably a hawk-like niche. Not sure if they ran or hopped.
Perhaps both tree-climbing and grasping were both critical, among both carnivores (theropods, hawk, hoatzal claw-winged bird) and other (2-toed sloth).
That is your conclusion; you still haven't explained how you have arrived at it.
This is because you have skipped the obvious question: birds clearly possess the ability to evolve spherical eggs. Why haven't all of them done so (except those that nest on cliffs) and thus erased the evidence for your claim?
Under no other circumstance can I imagine ovoid eggs being so strongly selected for in nature, as they are of inefficient form,
This is exactly why I would expect all birds except the cliff-nesting ones to have evolved spherical eggs ASAP. Yet, very few have. Something is wrong.
and must be rotated for the chick to survive, (unlike turtle eggs) which is hazardous on rocky cliffs.
This only shows that the requirement for rotation evolved before cliff-nesting did. It doesn't tell us anything else.
Why are kiwi eggs so huge? Why not a bunch of hummingbird-egg sized eggs?
A textbook example of K selection due to a scarcity of predators. If you don't know what K selection means, you should learn it -- a few pages of Google results should suffice.
However, the saber-toothed marsupial kangaroo & cat fossils found recently might provide a clue on how large eggs could have been consumed by early marsupial mammals.
There's no good evidence for marsupials in the strict sense before the Paleocene, and, obviously, marsupials from almost last week won't tell us much about the first marsupials.
Metatherians ( = marsupials and everything closer to them than to us) reach back to the early Middle Cretaceous, some 125 Ma ago; google for Sinodelphys -- and estimate whether a family of Sinodelphys would fit into an average oviraptorid egg (I guess it would).
Early marsupial bipeds
Uh... you do know that "bipedal" means "using only the hindlegs for locomotion", right? Because... I'm confused. However, we placentals and the marsupials are each other's closest living relatives, so live birth for their most recent common ancestor is by far the most parsimonious assumption.
This is not logical. Theropods have a very stiff back, and most of the tail is also very stiff. Titanosaurs, on the other hand, had never had stiff tails and had lost the back stiffening -- it might be relevant here that all known sauropod eggs seem to belong to titanosaurs.
They still haven't died out, and most of them do not nest on islands. Most nest on/in riverbanks. By your logic, they are all dead. Turtles bury their clutches; crocodiles guard and defend their nests... maybe defending the nest is the ancestral archosaurian condition...?
Conjecture: Lizards and snakes may have previously had hollow fangs used to puncture and siphon egg fluids (parallel mosquito), later saliva toxins or viral infections allowed more effective (less metabolically costly) predation upon other prey.
What about a few facts for a change?
- There are no lizards with hollow fangs.
- Within snakes, hollow fangs are restricted to colubroids, and those appeared in the Eocene or so, in any case after the end of the Cretaceous.
- Said fangs are connected to the poison gland, not to the mouth. It's impossible to drink through them.
You are making this up as you go along.
Why should anything perch in trees but nest on the ground?
Which theropods? Certainly not Allosaurus and Tyrannosaurus...?
OK, let's restrict us to those that were small enough, and let's have a look at their feet. Adaptations for perching? Only within birds, and probably in Scansoriopteryx/Epidendrosaurus. Contrary to earlier reports, even Archaeopteryx did not have a backwards-pointing first toe.
Oh, and, not that it matters, but the hoatzin is one of the few leaf-eating (folivorous) birds in existence. Has a few weird adaptations to that rather unique lifestyle.
No, insectivorous, and small enough in the adult to fit into a hen's egg. Herbivorous forms (seed-eating, superficially rodent-like ones) soon appeared, and later carnivorous ones up to the size of a cat also evolved (later growing even larger -- google Gobiconodon and Repenomamus), but seriously omnivorous mammals seem restricted to the Cenozoic. Specialized egg-eaters are not known among mammals at all (and are rare elsewhere -- think of that snake species in eastern Africa).
For lots more information on Mesozoic mammals, go to http://home.arcor.de/ktdykes/meseucaz.htm.
By David Marjanovi? (not verified) on 07 Mar 2007 #permalink
Briefly: ALL extant Aves spp. derive from cliff-nesting ancestors which survived a [ground egg predation] bottleneck, indicated by commonality of ovoid egg shape and flight feathers even amongst birds which do not fly.
"birds clearly possess the ability to evolve spherical eggs. Why haven't all of them done so (except those that nest on cliffs) and thus erased the evidence for your claim?"
Birds which returned to an enclosed-clutch nest (eggs can't roll out, parallel to sea turtle) as in owl and Baltimore oriole will revert to spheroid eggs, others won't.
"This is exactly why I would expect all birds except the cliff-nesting ones to have evolved spherical eggs ASAP. Yet, very few have. Something is wrong".
No, not wrong, just adapted to new predation situation (egg-constricting snakes?). Open nests in tree branches occurred long after cliff nesting selected for flight and ovoid eggs.
Evidence? Did theropods rotate their eggs?
"A textbook example of K selection due to a scarcity of predators. If you don't know what K selection means, you should learn it -- a few pages of Google results should suffice".
I presume that New Zealand may have had poisonous snakes but no constrictor snakes.
"There's no good evidence for marsupials in the strict sense before the Paleocene, and, obviously, marsupials from almost last week won't tell us much about the first marsupials".
I meant non-egg-laying mammals (or proto-mammals).
"Metatherians ( = marsupials and everything closer to them than to us) reach back to the early Middle Cretaceous, some 125 Ma ago; google for Sinodelphys -- and estimate whether a family of Sinodelphys would fit into an average oviraptorid egg (I guess it would).
Uh... you do know that "bipedal" means "using only the hindlegs for locomotion", right?"
Kangaroo-type bipeds.
[Sorry, I must attend a meeting now. More after.
http://darrennaish.blogspot.com/2006/05/dicynodonts-that-didnt-die-late…
The top left photo shows a tetrapod with what I'd refer to as "saber-tooth" condition, possibly it was a part-time egg eater, unless it was extremely small. I don't know if you'd classify it as a true mammal, but it's form is what I meant, able to walk, wade and swim in still water, able to climb mild inclines but not vertical cliffs, able to burrow soft sand and enter vegetative nests unless mother actively defended offspring, probably had poor color vision and good olfactory sense with primitive scent glands.
"Theropods have a very stiff back, and most of the tail is also very stiff".
Turtles share that condition yet hatch from spherical shells. Duck-billed dinos had ossified tails, I assume for better vertical posture while wading and walking.
"They still haven't died out, and most of them do not nest on islands. Most nest on/in riverbanks. By your logic, they are all dead".
No, the opposite. Turtles and crocs could swim to offshore isles easily, maintaining populations both ashore and on off-shore isles, they were never completely dependent on continental survival like the other egg layers. The dry dinos couldn't cross wavy ocean waters, so egg predators devastated the inland populations, leaving only the cliff dwellers and islanders.
[Possibilty: crocs and turtles were dino egg eaters? Some crocs ate molluscs]
"Turtles bury their clutches; crocodiles guard and defend their nests... maybe defending the nest is the ancestral archosaurian condition...?"
I don't know, perhaps until hatching.
Conjecture: Lizards and snakes -hollow fangs
"- Said fangs are connected to the poison gland, not to the mouth. It's impossible to drink through them."
OK, I thought the poison gland had derived from an invaginated salivary gland in the mouth, so a "straw suction" effect could have preceded the later toxic secretion.
Do you know when constrictors first developed? Constricting a large immobile egg would be easier than mobile prey, and may have been the first step towards modern constrictors (but tree climbing does same, required lianas or small stems or rough bark).
I think Early=Smaller theropods were arboreal-perching ground-nesters, probably a hawk-like (food-wise) niche. Not sure if they ran or hopped. The long central toe (runners toe) might indicate both running and perching.
Because it couldn't nest on the tree branches, it derived from sand-nesters. It laid eggs in an open "crater" of some sort, and while perched in tree branches was able to see egg predators and attack them, but was unable to see underground burrowing predators, so incubation was rewarded by greater survival of off-spring.
"Which theropods? Certainly not Allosaurus and Tyrannosaurus...?"
Larger theropods didn't perch.
"OK, let's restrict us to those that were small enough, and let's have a look at their feet. Adaptations for perching? Only within birds, and probably in Scansoriopteryx/Epidendrosaurus. Contrary to earlier reports, even Archaeopteryx did not have a backwards-pointing first toe."
If the toe claws were straight, then they didn't perch (T Rex). If the longest toe claws were sharply curved, they could perch without rearward claws, although not as well as perching birds.
"Oh, and, not that it matters, but the hoatzin is one of the few leaf-eating (folivorous) birds in existence. Has a few weird adaptations to that rather unique lifestyle".
Yes, I forgot, thanks.
I'm not referring to ultra-specialized egg eaters, rather more likely opportunistic part-time egg eaters.
"For lots more information on Mesozoic mammals, go to http://home.arcor.de/ktdykes/meseucaz.htm."
That link doesn't work (German: non-operational)
I guess the alternative to the cliff nesting scenario would be this:
Theropod spiral nest, improved habitual flight selected for reduced redundancy of organs (single functional ovary) and smaller clutches (lighter weight inflight, so more clutches per year required) oblong eggs became truncated (more ovoid-like) for better arboreal maneuverability inflight, habit of vegetative cover on ground nest and more arboreal perching resulted in arboreal nesting. Does this make sense to you?
Turtles have a rigid back but do not have the long tails present in theropods. This kind of animal will fit better into an ovoid egg. Spherical eggs are only more efficient in terms of surface area relative to volume. Ovoid eggs may be more efficient when laying them- an animal may well be able to lay a larger egg, and produce a larger hatchling, if the egg is long and narrow, than if the same sized animal laid a spherical egg. Turtle eggs are very small compared to the size of the mother, and are laid in large numbers. Birds lay a few eggs and produce much larger offspring reltive to the size of the adult.
It should be remembered that many ovoid dinosaur eggs re fairly sausage-shaped and would happily roll off a cliff. As will hen's eggs. The eggs of guillemots are very unusual in being extremely pointed. IIRC guillemots don't make much of a nest either, so their eggs are at particular risk of falling off a cliff.
Dicynodonts (the animal in your link) were, from what we can tell, obligate herbivores. The tusks were used for defence or intra-specific competition. Not egg eating.
The giant carnivorous kangaroos and Thylacosmilus are much more recent than any dinosaur, and were specialist carnivores. Early marsupials are all much, much, smaller than these animals. Repenomamus is very unusual for a mesozoic mammal.
Extant birds being descended from more primitive flying ancestors says very little about the ancestral reproductive behaviour. I suspect differences in metabolic rate and perhaps reproductive strategy (specifically K and r selection strategies) are far more important in determining the survival of the Neornithines and the extinction of the Enantiornithines.
Try this link for Trevor Dykes' website.
First of all, the link to http://home.arcor.de/ktdykes/meseucaz.htm works as soon as you remove the period behind it (as I have just done). Internet addresses never end in a period, even though the scienceblogs layout engine doesn't know that.
Secondly, the HTML tag you are looking for is <blockquote>. Put this in front of quoted material and </blockquote> behind it, and it will appear like the quotes in this post. As you can see below, you can nest several such tags within each other.
<i> for italics and <b> for bold work the same way.
birds clearly possess the ability to evolve spherical eggs. Why haven't all of them done so (except those that nest on cliffs) and thus erased the evidence for your claim?
The vast majority of birds have nests in trees where the eggs can't roll out. Most of them have ovoid rather than spherical eggs.
No, not wrong, just adapted to new predation situation (egg-constricting snakes?).
Why would any snake in its right mind constrict an egg?!? The egg would just break in the middle, and all the liquid would spill out, making it just about impossible for the snake to get any of it into its mouth. Hint: there are no egg-constricting snakes.
Open nests in tree branches occurred long after cliff nesting selected for flight and ovoid eggs.
Then what is the difference between an owl and a woodpecker?
Evidence?
If you need to rotate your eggs on a cliff, you are exposing them to unnecessary danger. Obligatory rotation is thus not recommended for a cliff-nester. It follows that obligatory rotation evolved first and cliff-nesting evolved later. Perhaps much later.
Did theropods rotate their eggs?
Lourinhanosaurus, troodontids, and oviraptorids didn't, their eggs stuck in the ground. I don't know about the nest attributed to Deinonychus. On the other hand, we don't know where within birds egg rotation evolved. All extant birds do it, but beyond that we don't know, unless someone has figured out what a Laevisoolithus egg looked like (this is an eggshell type attributed to Enantiornithes).
There are no snakes in New Zealand. Period.
Then say so. :-)
Only kangaroos (and various rodents) are kangaroo-type bipeds -- and only the large kangaroos are; the potoroo, for example, is largely quadrupedal. This is a quite recent innovation; a normal marsupial looks more like an opossum.
The top left photo shows a tetrapod with what I'd refer to as "saber-tooth" condition, possibly it was a part-time egg eater, unless it was extremely small. I don't know if you'd classify it as a true mammal
Oh man. That's a dicynodont. The dominant plant-eaters of the Middle Permian to Early Triassic. The depicted species should be pig- to cow-sized. The two teeth you can see are the only teeth the animal has, and they are round in cross-section, not blade-shaped, and lack enamel. That's the opposite of a saber-tooth. Sure, they are more closely related to the mammals than to any other extant animals, but they are still far away, and as large herbivores they don't matter here in the first place.
Remember: Google is your friend.
They still haven't died out, and most of them do not nest on islands. Most nest on/in riverbanks. By your logic, they are all dead.
Three major mistakes in your thinking:
- You tacitly assume that something changed right before the end of the Cretaceous. But neither the mammals nor anything else did. All your potential egg-eaters had existed alongside the dinosaurs (and the crocs and the turtles) for at least 140 million years. This is why a grand total of zero vertebrate paleontologists accepts the old speculation that the dinosaurs were done in by egg-eaters.
- You tacitly assume that the extinction of the dinosaurs needs to be explained. Yet, some dinosaurs (Neornithes: the modern birds) survived, while many other animals, plants, and microorganisms died out, on land, in the sea, and in the air. The whole mass extinction must be explained; you can't pick some parts of it and ignore the others. That's what planetoid impacts are for.
- Most turtles and crocodiles today don't have any remote islands at their disposal and live far, far away from "wavy ocean waters". Some can't even swim reasonably -- think tortoises.
Crocs, why not on occasion. Turtles, certainly not.
My point is that a well-defended nest will not be robbed.
OK, I thought the poison gland had derived from an invaginated salivary gland in the mouth,
so a "straw suction" effect could have preceded the later toxic secretion.
I don't understand that at all. Sucking stuff into the salivary/poison gland is good for nothing, and it's not even possible (because there are no muscles that distend such glands).
Importantly, poison glands way precede specialized teeth for poison injection. Lots of snakes and "lizards" have the former but not the latter.
Do you know when constrictors first developed?
Maybe in the middle Cretaceous (that is 40 million years before the end of the Cretaceous).
Constricting a large immobile egg would be
a very bad idea, see above.
I think Early=Smaller theropods
There's no good correlation between time and size. The earliest known theropods are Guaibasaurus and a couple of coelophysoids -- all far too large to perch.
were arboreal-perching ground-nesters, probably a hawk-like (food-wise) niche. Not sure if they ran or hopped.
Plenty of adaptations to running, none to climbing or perching...
The long central toe (runners toe) might indicate both running and perching.
It has nothing to do with perching.
Without a backwards-pointing toe you can hardly perch at all. Surely perching for a living would exert some selection pressure towards the evolution of such a toe, don't you think?
Fine -- shrews still don't plunder hens' nests.
[...] Does this make sense to you?
Whether it makes sense to me or anyone is totally beside the point. :-) The only thing that's important is whether it's scientific: you must ask yourself the question "If I were wrong, how would I know?".
Obviously, if you figure out this way that you are in fact wrong, you know what to do.
http://www.amnh.org/science/papers/mesozoic_mammal.php
mentions repenomamus bipedal behaviour, predation on extremely young prey (post-embryo) likely in or near nest. Lack of molars is expected in egg and nestling eaters I'd think, prominent muscular jaws and incisors/canines expected.
I expect birds with spherical eggs have enclosed clutches (inside tree hollow) where eggs can't roll out and break. The pink headed duck is said to have spherical eggs, I expect it once nested in hollow trees like American wood ducks or alternatively buries its eggs in soft sand.
Most bird nests are open for easy and swift access by parents, to allow fast feeding of fast growing (relatively) large brood. This indicates that food consumption of offspring is more significant than predation on young. Note that cliff nesters like murres (penguins) have very small broods. It is expected that arboreal open-nest birds have more rounded eggs and larger broods than cliff nesters, and more ovoid eggs than enclosed clutch nesters.
There are no egg constrictors? I don't know, but constriction may have begun with small-ish snakes crushing over-sized eggs. Large diameter snakes don't burrow as much as small diameter snakes.
I expect both the owl and woodpecker have well rounded eggs as well the wood duck.
Evidence (of early rotation of pre-avian eggs)?
"If you need to rotate your eggs on a cliff, you are exposing them to unnecessary danger. Obligatory rotation is thus not recommended for a cliff-nester. It follows that obligatory rotation evolved first and cliff-nesting evolved later. Perhaps much later."
This strikes me as extraordinarily weak "evidence", but I guess it must make sense to you. To me, rotation fits perfectly with natural selection working upon cliff nesting birds, but has no selective benefit on ground nesting animals so would not have been strongly selected.
However having said that, I realized that I don't even know for sure that murres rotate their eggs, I merely assumed they do. Oops.
I must go grab lunch.
To Dave Godfrey,
thanks for refs, I don't generally view dino eggs as ovoid (though many have slight ovoid shape), they seem to be largely oblong, spherical or partly ovoid.
Regarding bird eggs, John Hawks mentioned harassing cow birds here.
I wonder if cowbirds are effective predator controllers, do they harass predators or make lots of noise, more so than average birds? This would explain the bullying over the warblers nesting.
If the cowbirds did not provide assistance against predators, surely the warblers would peck a hole in the cowbird's egg or otherwise not warm it.
Although I may be wrong, I still think that ovoid eggs in birds were due to cliff nesting during a bottleneck, which changed the internal egg production system in conjunction with the development of improved flight and feathers, and that a cosmic impact or the Deccan traps may have played significant parts, it was primarily the combination of egg laying and predation on eggs that was responsible for massive extinction. That marine plants and animals also had extinctions is not surprising, since the same occurred there at the sandy shores, but not on vertical cliffs.
I'm sorry to hear that paleontologists have discarded this idea in favor of catastrophism.
mentions repenomamus bipedal behaviour,
No, it does not. Read the page again.
predation on extremely young prey (post-embryo) likely in or near nest.
Yes, but:
Lack of molars is expected in egg and nestling eaters I'd think, prominent muscular jaws and incisors/canines expected.
It has plenty of molars. It just has retained the normal mammalian molar shape (three cusps in a straight row). Unable to chew (because the teeth don't occlude precisely enough), it is what a carnivorous cynodontian that eats prey smaller than itself normally looks like. It's a triconodont -- far away from placentals and marsupials, almost as far away as the monotremes are.
And don't forget: as much time (65 Ma) lies between Repenomamus and the Cretaceous-Paleogene boundary as between the boundary and now.
Sounds good. -- Wikipedia seems to have a taboo against mentioning the shape of woodpecker eggs. However, the German article on the Eurasian wryneck says its eggs are 21 x 16 mm. Not spherical, even though it broods in treeholes.
It is expected that arboreal open-nest birds have more rounded eggs and larger broods than cliff nesters, and more ovoid eggs than enclosed clutch nesters.
What stops them from having spherical ones? If ovoid eggs are so costly, why does any bird except the cliff-nesting ones have them?
There are no egg constrictors?
Of course not! Snakes can't lick liquids from the ground, and they can't suck at all! They can only swallow, and that's what egg-eating snakes do. Breaking an egg when it's outside their digestive tract is against their interests.
I don't know, but constriction may have begun with small-ish snakes crushing over-sized eggs.
Snakes started as quite large animals, and the boids just kept that size. Burrowing seems to be an innovation. A snake crushing an egg would win a Darwin Award.
None. I only say that eggs must be able to rotate before cliff-nesting can evolve. When crocodile eggs are rotated, the embryo dies.
Fine, I've got a better argument: How can the process get started when rotation kills the embryo? First the ability to survive rotation must evolve, then cliff-nesting becomes possible. The other way around it's impossible.
Well, as scientists, we must go wherever the evidence leads us, whether we like it or not. The evidence for a catastrophic mass extinction produced by the Chicxulub impact is simply overwhelming. On the other hand, there is (I repeat) zero evidence for increased egg-eater activity at the Cretaceous-Paleogene boundary, and evidence against an increased presence of potential egg-eaters at that time.
(Admittedly, I do like it, but that doesn't matter.)
it was primarily the combination of egg laying and predation on eggs that was responsible for massive extinction.
I forgot to mention: you can't eat the eggs of a mosasaur or plesiosaur any more than those of a stagodontid or "pediomyid" metatherian. They didn't lay any. They were viviparous. Gravid specimens have been found.
You can eat the eggs of an ammonite or rudist. You'll just never find all of them.
And how do you wipe out all cheirolepidiacean trees? And decimate the haptophytes (coccolithophores, calcareous nannoplankton)? And so on and so on.
I don't generally view dino eggs as ovoid (though many have slight ovoid shape), they seem to be largely oblong, spherical or partly ovoid.
"Ovoid" is a poorly defined word, it just refers to something oval- which encompasses all sorts of rounded shapes- while I suspected you were restricting it to the typical egg-shaped ovoid, I thought it wise to mention that dinosaur eggs could also be referred to as ovoid- even though most of the known ones aren't the same shape as a hen's egg.
I still don't see that spherical eggs are more efficient. As mentioned before non-spherical eggs allow an animal to produce a larger egg (and hence larger hatchling). This is important for birds as they don't fly until nearly fully grown.
Many dinosaurs were too large to incubate their eggs and would have buried them. While some may have abandoned them at this point others (eg Maiasaura) clearly guarded them and brought food to the hatchlings.
That first paragraph is a quote from DDeden
"Although Repenomamus probably could not run fast, it could stand on its hindlimbs and walk effectively enough to stalk small prey-as this new fossil of R. robustus indicates."
Is that not functional bipedal locomotion, like a bear or chimp?
(Unlike human or gibbon obligate bipedalism)
I figure bears-badgers and hominoids-hominids merely continue the proto-mammal egg carnivory/small animal carnivory/insectivory (grubs) /frugivory/foliovory mixed omnivory. Since the dentition was still in the process of evolving, they had more primitive teeth, unlike modern omnivores.
" as much time (65 Ma) lies between Repenomamus and the Cretaceous-Paleogene boundary as between the boundary and now."
I consider Repenomamus to represent a form, which reoccurred as a marsupial and eutherian later on, similarly to how saber-tooth carnivorous tetrapod filled an ecological niche which occurred repeatedly producing slightly different varieties (smilodon, marsupial saber tooth, saber-tooth kangaroo, saber-tooth walrus).
Regarding spherical bird eggs, it would be hard to predict the exact roundness of a bird egg based only on nest type, but tree hollow nesters would be expected to have rounder eggs than open nest (tree or ground) and rocky cliffs).
"If ovoid eggs are so costly, why does any bird except the cliff-nesting ones have them?"
They shifted from large (spherical) egg masses & precocial young to few eggs per clutch and altricial young during the cliff nesting stage. In this sense they upgraded on the food chain, becoming more apex-predator-like due to flight niche. The need to return to large egg masses has not redeveloped due to greater comparative fitness (birds vs reptile, birds vs amphibian, birds vs mammal), where flight allowed new forms of predation and foraging success as long as the nest was protected.
"I only say that eggs must be able to rotate before cliff-nesting can evolve. When crocodile eggs are rotated, the embryo dies."
Cliff nesting occurred at the same time as ground nesting, egg were riskier on cliffs environmentally, riskier on ground predatorially.
Nature selected for mutations allowing bird eggs to be slightly rotated, and them more so, due to inbreeding among avian survivors on offshore (not remote) isles.
Egg cracking rather than egg crushing snakes, just enough compression to break the shell surface, then with mouth underneath, fluids drain.
Seems unlikely, but not impossible.
"How can the process get started when rotation kills the embryo? First the ability to survive rotation must evolve, then cliff-nesting becomes possible. The other way around it's impossible."
The same reasoning goes for dolphins, they first had to dive well before they entered the water, otherwise they would drown. Circular reasoning I think.
The first birds laid their eggs anywhere (as murres still do), most eggs got eaten, the ones on cliffs didn't (no egg predators on island cliffs at that time) but were selected for non-sphericity, the limiting agent of non-sphericity was embryological dependence on rolling (accidental rotation) but not rolling off cliffs. This accidental rotation became instinctual, and is now common even among birds which abandoned cliffs long ago (but not sure about owls, pink-headed ducks).
I agree the cosmic impact is certainly major, but the bird-feather-egg connection is just too sensible to ignore, and the coexistence of known marsupials is serendipity.
"you can't eat the eggs of a mosasaur or plesiosaur any more than those of a stagodontid or "pediomyid" metatherian. They didn't lay any. They were viviparous."
Why? Natural selection against oviparous, those which hatched within had better chance of survival against heavy predation. I assume their forebears had laid their eggs on the shore grounds, and those forebears were limited to continental shores, not islands (Differs from turtles).
Regarding ancient plants, I don't know...climate change I guess and small climbing mammals and birds eating fruit/nuts (parallel to rats decimating jujuba palm nuts on Easter Island causing decimation of forest?).
Calcareous algae, change in water chemistry I'd guess.
Ovoid egg: can't roll straight down slight incline, must roll an arc.
Sphere egg: rolls straight down slight incline.
Oblong egg: rolls straight down slight incline.
Sauropod egg: rolls straight down slight incline.
Some theropod egg: rolls straight down with slight wobble AFAIK.
I assume that the squished look of theropod eggs is due to fossil compression, and originally they were circular in cross section and oblong from a side view (with possible very slight ovoid effect).
"I still don't see that spherical eggs are more efficient."
Much less calcium required for sphere than any other shape, original shape of ova cell is sphere.
"As mentioned before non-spherical eggs allow an animal to produce a larger egg (and hence larger hatchling). This is important for birds as they don't fly until nearly fully grown."
Yes, but also true of oblong eggs, yet how many birds produce oblong eggs? All birds walk before they fly, (parallel ontologically to theropods walking before cliff nesting selected for flight), ducks walk, then swim, then fly (parallels early loon-like Avian).
Is there evidence of food-provisioning to offspring at nest, or is that a deduction? I figured the theropods would accidentally provision young by simply carrying back a snack to the nest area for itself, and the young would nibble at it. By the time of cliff nesting, provisioning instinct would necessarily be strong, since rocky cliffs bore little food but rich water/land foods were just a short flight away.
Oh! No, it's not -- it's a poorly formed sentence. R. could a) "stand on its hindlimbs" and b) "walk effectively enough" on all fours. The latter part is emphasized to explain the concept of a sprawling mammal to people.
What would bipedality have to do with egg-eating, anyway?
I figure bears-badgers and hominoids-hominids merely continue the proto-mammal egg carnivory/small animal carnivory/insectivory (grubs) /frugivory/foliovory mixed omnivory.
You are overestimating the ancestral size for mammals. Normal (unmodified) mammals are shrew-sized, not rat-sized. Accordingly, they have the teeth of insectivores, with lots of very tall, very thin cusps that make omnivory difficult. Shrews retain this condition.
Since the dentition was still in the process of evolving
The dentition, like everything else, is always in the process of evolving, and it cannot stop as long as anything in the environment changes.
as much time (65 Ma) lies between Repenomamus and the Cretaceous-Paleogene boundary as between the boundary and now.
Fine. In this case, why didn't R. trigger a mass extinction? How did the speculative mammals that according to you suddenly appeared at the K-Pg boundary differ from R. in their egg-eating ability?
Regarding spherical bird eggs, it would be hard to predict the exact roundness of a bird egg based only on nest type, but tree hollow nesters would be expected to have rounder eggs than open nest (tree or ground)
And if so, what happens if I show that nesting anywhere else than on cliffs is the ancestral condition for extant birds? Doesn't your speculation fly out of the window then?
If ovoid eggs are so costly, why does any bird except the cliff-nesting ones have them?
They shifted from large (spherical) egg masses & precocial young to few eggs per clutch and altricial young during the cliff nesting stage.
No, precocial young are the normal state of affairs for extant birds. This condition is retained throughout the paleognaths, the anseriforms and galliforms, and then some.
The same, incidentally, seems to hold for nesting on the ground.
In this sense they upgraded on the food chain, becoming more apex-predator-like due to flight niche.
The need to return to large egg masses has not redeveloped due to greater comparative fitness (birds vs reptile, birds vs amphibian, birds vs mammal), where flight allowed new forms of predation and foraging success as long as the nest was protected.
The protected nest allowed to have fewer and larger young.
I only say that eggs must be able to rotate before cliff-nesting can evolve. When crocodile eggs are rotated, the embryo dies.
So you agree: egg rotation had to evolve before all but the very beginning of cliff-nesting. :-)
Seems completely impossible considering the lack of flexibility of snake lips. Remember that these aren't mammal lips: they are stiff flaps of skin with large scales, not soft affairs that consist mostly of muscle.
How can the process get started when rotation kills the embryo? First the ability to survive rotation must evolve, then cliff-nesting becomes possible. The other way around it's impossible.
Just about all mammals can swim, and few or none will drown when just thrown into water.
That's a beautiful just-so story. Now ask yourself: if you were wrong, how would you know?
I agree the cosmic impact is certainly major, but the bird-feather-egg connection is just too sensible to ignore
What connection?
I honestly don't have an idea what you mean.
and the coexistence of known marsupials is serendipity.
I don't understand that either.
you can't eat the eggs of a mosasaur or plesiosaur any more than those of a stagodontid or "pediomyid" metatherian. They didn't lay any. They were viviparous.
And can therefore not have been extinguished by egg-eaters, was my point. Yet, they all died out at the same time.
Why do you keep making up improbable speculations when you don't need to? The impact explains it all just fine -- better yet: because we know the size of the impact, we expect that there was a mass extinction, and not finding a mass extinction at the same time as such an impact would be a major surprise.
Quite so: the impact made the top layers of the sea massively acidic (sulfuric acid from rock vapor from the impact site, nitric acid from the burnt air, carbonic acid from rock vapor and from the burnt forests). Same for the "climate change" you pulled out of thin air above.
I still don't see that spherical eggs are more efficient.
Much less calcium required for sphere than any other shape,
Why do you assume that calcium is a limiting factor? A calcium deficiency is difficult to get except maybe for obligatory herbivores living in limestone-free areas.
ducks walk, then swim, then fly (parallels early loon-like Avian).
Have a look at a phylogenetic tree of Aves with ducks in it.
Is there evidence of food-provisioning to offspring at nest, or is that a deduction?
What do you mean? There's no fossilized food, but nests have never been found in rocks that would preserve it. What about deductions from young that clearly couldn't feed themselves?
I'll consider your statements and respond soon, thanks.
"The impact explains it all just fine"
OK, I didn't know that. The birds, crocs and turtles survived, how/why?
2 side questions:
65ma, were there likely to have been a great number of off-shore isles? I ask because all the pre-pleistocene maps I've seen distinctly lack abundant off-shore isles. The modern tropical off-shore isles are heavily forested with fruit trees seeded by fruit bats/flying foxes which roost on coastal mangroves. Remote temperate isles tend to lack mangroves and fruit bat refugia, and so become barren guano laden seabird colonies of bare rock and grass. Based on this, I figure the KT ancestral birds, crocs and turtles survived on tropical mountainous reef-rich offshore isles (not too close but not too remote from continents, and not low-lying coral atolls) which lacked mammals, and this is where birds eventually evolved arboreal nesting after having gone through the cliff nesting period. Relevant to Darren's post on non-flying bats, I'd think that the most likely place to have had flight-less bats would have been western Polynesia before the Polynesian (human) dispersal and perhaps the Seychelles etc.
Early Ichthyosaurs lost their thumbs (you mentioned in a 2001 post elsewhere IIRC), is it likely due to the lesser need for turning/reversing on traction surfaces, and the replacement of that function with the whole fin and tail rudder complex used to turn in water? That Sirenians and cetaceans didn't lose their thumbs as they evolved fins would seem to indicate a different form of habitual locomotion and niche.
Sorry for drifting so far from theropod feathers.
Why not? :-) First, note that lots of birds did die out (though we can't tell exactly when -- the fossil record is too poor), turtles decreased at least in numbers, and specialized turtle-eating crocs died out.
Birds similar to a chicken or tinamou (or screamer) don't depend on green plant parts directly or indirectly, so they are (relatively) likely to survive. The same holds for freshwater ecosystems in general, and there go the turtles and the crocs.
None of this is new -- it has all been proposed over 10 years ago.
65ma, were there likely to have been a great number of off-shore isles? I ask because all the pre-pleistocene maps I've seen distinctly lack abundant off-shore isles.
Difficult to tell -- there's not much evidence either way.
The modern tropical off-shore isles are heavily forested with fruit trees seeded by fruit bats/flying foxes which roost on coastal mangroves. Remote temperate isles tend to lack mangroves and fruit bat refugia, and so become barren guano laden seabird colonies of bare rock and grass. Based on this, I figure the KT ancestral birds, crocs and turtles survived on tropical mountainous reef-rich offshore isles (not too close but not too remote from continents, and not low-lying coral atolls) which lacked mammals, and this is where birds eventually evolved arboreal nesting after having gone through the cliff nesting period.
The impact happened into the sea. It probably emptied the Gulf of Mexico. A tsunami swept across Florida into the Atlantic. I do not consider any coasts a likely place to survive that.
Relevant to Darren's post on non-flying bats, I'd think that the most likely place to have had flight-less bats would have been western Polynesia before the Polynesian (human) dispersal and perhaps the Seychelles etc.
Apart from the Seychelles and Fiji, those islands are mostly too young, and the Seychelles and Fiji both have frogs; Fiji has lizards, too (I don't know about the Seychelles, but I bet they also have some). That may be too much competition. Of course, NZ has frogs and lizards and the tuatara -- maybe that's why the mystacinids never lost flight.
Early Ichthyosaurs lost their thumbs
is it likely due to the lesser need for turning/reversing on traction surfaces, and the replacement of that function with the whole fin and tail rudder complex used to turn in water?
No idea. I can only guess that it didn't have any disadvantages -- and losing something always saves energy.
That Sirenians and cetaceans didn't lose their thumbs as they evolved fins would seem to indicate a different form of habitual locomotion and niche.
Well, their fins are so different in architecture from ichthyosaur fins that I don't think they are comparable in this respect.
Any opinion on this paper, stating the impact occurred 300k yrs before the extinction?
http://www.pnas.org/cgi/content/abstract/101/11/3753
"The impact happened into the sea"
Based on the pictures, I would have thought the impact occurred quite some distance inland and has since "moved seawards" due to coastal erosion in the last 65m years. Are you saying that the Yucatan peninsula was actually under the sea, and has since uplifted? Or that there has been almost no coastal erosion since the impact?
Yes. The good people have overlooked the fact that inside the crater they must not expect neat layers -- they must expect humongous boulders that fell in when the primary crater walls collapsed. The primary crater must have been (as can be calculated) a hole tens of km deep with, near the top, more or less vertical walls. I bet they've bored through one of these boulders.
I don't know if it has been uplifted -- it wouldn't surprise me, though, as an effect of the subduction of the Cocos plate under Mesoamerica --, but the sea level has drastically dropped since the Cretaceous. This is easy to understand: for one thing, there was no inland ice back then, not even in Antarctica, and the water had to go somewhere.
Coastal erosion has almost no effect over hundreds of thousands of years. At this timescale and above, the sea goes, and the sea comes.
Yes, a boulder or so is likely.
I disagree only on the magnitude of coastal erosion, I think the tidal erosion-deposition displacement cycle is very significant geologically and may even be the primary causative agent of tectonic continental drift ie. the splitting and re-combining of super-continents, but this is mere speculation.
95ma burrowing dino
http://news.bbc.co.uk/2/hi/science/nature/6472579.stm
This dino does not look much like a burrower (no large front claws), does their scenario appear to be sensible to you? Firm soil was needed to establish the den, did they use their rear legs?
Regarding the hypothesized association between the coastal solar-lunar tidal erosion cycle (producing continental shelves), continental drift, seismic global humming and polar winter pack ice influence on geologic chokepoints, please see my URL. This is the reason I'm interested in the determining of continental off-shore islands in the last 200ma.
I'm not sure how you know about the lack of large front claws, as, according to the accompanying illustration there is no material from the hands preserved. The shoulders and pelvis are much more well muscled than otherwise expected. That indicates to me that it would have been a reasonable digger. Its not an underground specialist, but something much more like a hyaena in behaviour, nesting below ground during the breeding season to protect its young, and possibly hibernating/aestivating.
Thanks Dave, ok, I was thinking along the lines of a badger.
Think again. Please! Continental crust reaches all the way down to 70 km below sea level. It's obvious that coastal erosion can't do anything about that. The driving agent behind plate tectonics is heat leading to convection. If you can, do the math... (I can't.)
This dino does not look much like a burrower (no large front claws), does their scenario appear to be sensible to you?
Yes. While no claws are known, there are plenty of other features that only make sense for a digger (though something as specialized for digging as an armadillo or mole). The pdf of the paper and the pdf of a review article about it are free access somewhere at http://pubs.royalsoc.ac.uk -- you'll find it.
Thanks David. (BTW the URL referred to in my 3:23am post can be reached by clicking on the blue colored DDeden)
I think you meant "(though NOT something as specialized for digging as an armadillo or mole)", correct?
Regarding continental crust, it matters not how thick it is, but how dense it is, relative to the underlying magma and the overlying atmosphere/hydrosphere. How did the islands now occupied by the UK & Ireland behave when thick dense glaciers were piled on top? They lowered towards the center of the Earth (probably bridged to the rest of Europe), compressing the ~70km of crust beneath towards the mantle. Now they are still rising on the rebound in some parts after glacial melting.
Geothermal convection IMO explains the ability of continents to drift, AFAICT it does not explain migratory propulsion of land masses along the convex surface (parallel to a floating iceberg).
Icebergs drift upon a denser fluid medium (seawater) hydrosphere following mechanical currents which are powered by lunar-solar tidal differentials, not by geothermal convection currents. Since tectonic plates also float upon a spherical sea of fluid magma/mantle, I would expect them to also react to lunar-solar effects, in addition to the change in mass at continental shelves and the continuously highly erosive shores. The result is a supercontinent at the pode, then splitting and reassembly at the anti-pode, due to this extra-terrestrial forced terrestrial tide. A parallel: a recent arctic storm caused an antarctic ice sheet to break away, due to the shock-wave along the convex hydrosphere.
AFAICT the only "engine" for the convex locomotion of continents/tectonic plates is the relative position of the Earth to the sun and moon etc.
Geothermal convective currents are reactionary to the extra-terrestrial environment, if not Earth would be a static stratified non-tidal lump of iron with immobile silica sheath I guess.
In the same way, the sun's convective currents depend upon the relative positions of the equatorial planets.
Since I've drifted from feathers again, let me end with this non-tetrapodal-non-zoological speculation:
Specific gravity = density. Gravity = density. always.
(Any more non-TZ talk might be better at my blog?)
I just saw this, relates to early mammals and dinos:
Caroline M Pond 1977
The significance of lactation in the evolution of mammals
Evol.31:177-199
"The effects of viviparity, lactation and other forms of postnatal parental feeding upon the anatomy and energy budget of the parent and growth and development of the young are compared. Lactation makes the young nutritionally dependent upon the mother, but mechanically independent of
her, at least for part of the time. he advantages of these circumstances to the parent and the young are explained. Compared to viviparous reptiles and lower vertebrates, mammalian fetuses are relatively small at birth, but
through lactation the mother continues to supply most or all of the juveniles' food until they reach a large fraction of the adult size. I propose the hypothesis that it is lactation, not viviparity which is the unique feature of mammalian reproduction that has made possible the evolution of diphyodonty, dentition composed of a limited number of
accurately occlusible teeth, rapid growth to maturity and mutualistic social behavior. I argue that even in large species, lactation and other forms of parental processing of the juveniles' food enable them to be weaned directly
onto the adult diet, whereas reptiles of similar size require different diets at different growth stages. I suggest that the decline of large reptiles at the end of the Mesozoic may have been due to the climatic and floristic changes at that time making it difficult for their relatively small young to find suitable food unaided. Species which practiced suckling or parental processing of food for the juveniles would be favored because the larger, most robust and adaptable parents subsidized the diet of the
juveniles through their vulnerable early growth stages."
Any opinion? It fits with my thoughts, but doesn't mention egg-eating.
Egg-eating isn't relevant. Also note the date of the paper, published before the Alvarezs' papers were published and long before gained wide acceptance.
At the time it was assumed that the dinosaurs were on the way out, and the evolution of flowers was blamed. This correlation does not exist, and dinosaur extinction was a much more sudden event than was believed then. They might have been suffering for a million years or so before the final impact (as a result of the eruptions in the Deccan Traps)- but this is nothing compared to the length of time that they co-existed with mammals and flowers.
I can see lactation as providing an advantage to mammals in that they are not so dependant on multiple food sources at different stages in their lives (as pterosaurs appear to have been). I can see it being important in the mammals' diversification into the vacant niches after the K/T extinction, but I suspect that luck and small size was more important in actually surviving the K/T extinction.
Oops, yes. I must not comment blogs after 2 am. I must not comment blogs after 2 am. I must not comment blogs after 2 am...
I'll try to read your website today evening.
Sorry, it's normally 30 km, 70 is for mountain ranges...
I don't know if the British Isles are still rebounding (but, anyway, the Baltic Sea is). Yes, the weight of the ice did press them down into the more liquid asthenosphere; this effect was, however, more than offset by the drop of the sea level which connected them to the rest of Europe. (There's no "probably" about this.)
I don't see where the difference between these two is.
Icebergs drift upon a denser fluid medium (seawater) hydrosphere following mechanical currents which are powered by lunar-solar tidal differentials, not by geothermal convection currents. Since tectonic plates also float upon a spherical sea of fluid magma/mantle, I would expect them to also react to lunar-solar effects, in addition to the change in mass at continental shelves and the continuously highly erosive shores.
Remember: the worst math is no math at all.
There is no convection in the sea because it's warmed from above, not from below. There is convection in the mantle because it's warmed from below, not from above.
The tidal effects exist, but they are far, far too small to have anything measurable to do with plate tectonics.
You have way overestimated coastal erosion. No -- worse: you have not estimated its magnitude at all. There is no science without math.
How did you manage to miss the fact that radioactive decay produces heat?
Mind you: there are bodies too small to produce much heat by radioactive decay but which are nevertheless active. The prime example is Io: its heat does come from the tidal effects of Jupiter. The Earth is in the opposite situation: big enough for heat from radioactivity (the math has, of course, been done), too big and too far away from everything else to be influenced that much by tidal kneading.
But surely you haven't missed the fact that nuclear fusion generates heat!?!
Specific gravity = density.
By definition correct.
Gravity = density.
Wrong. Gravity is a force, not a property of a body.
Darren needs the blog hits :-)
"I suggest that the decline of large reptiles at the end of the Mesozoic may have been due to the climatic and floristic changes at that time making it difficult for their relatively small young to find suitable food unaided."
1. She doesn't "suggest" that, she speculates.
2. There were no climatic or floristic changes, other than those directly caused by the impact.
3. By her logic, we'd expect e. g. the crocodiles to have died out, but we would expect no mass extinction in the sea whatsoever.
4. By her logic, we'd expect all of that to occur much earlier. Let's take a time of considerable climatic and floristic changes: the Cenomanian.
They might have been suffering for a million years or so before the final impact (as a result of the eruptions in the Deccan Traps)
Does not look like it. During the biggest episode of flood basalt outpouring, the global average temperature climbed by 3 °C, and when it ended -- IIRC 100,000 years before the end of the K --, things went back to normal. That is, apparently, all. No suffering has been noticed in the dinosaur fauna, even in the Hell Creek Fm which has enough temporal resolution.
Does not look like it. During the biggest episode of flood basalt outpouring, the global average temperature climbed by 3 �C, and when it ended -- IIRC 100,000 years before the end of the K --, things went back to normal. That is, apparently, all. No suffering has been noticed in the dinosaur fauna, even in the Hell Creek Fm which has enough temporal resolution.
Interesting. If the Deccan Traps outpouring had no significant effect on dinosaur diversity that has serious implications for blaming the Permo-Triassic event on the Siberian flood basalts.
Is there evidence for any effect of the Deccan traps on any part of the biosphere?
Thanks Dave.
Importantly, both mammals (exc. monotremes) and (in parallel) angiosperms (fruiting flowering plants) have mobile "egg/seed/newborn" stage, a huge advantage over immobile eggs/seeds in certain circumstances (eg. non-flight terrest./marine seasonal migration in mammals, floating fruit with edible nutritive pulp and indigestible seed in angiospermae).
Are/were there any primarily frugivorous marsupials? I'd think not. Perhaps this all relates to the earlier P-T extinction (or other), rather than the K-T extinction?
David, thanks,
"I don't see where the difference between these two is". Interior heat diffuses equilaterally outwardly as a balanced continuous flow. Tidal energy never diffuses equilaterally upon the Earth, it is by it's nature asymmetrical yet in equilibrium (see the light-dark pic of Earth at bottom of my blog), which gives a continuous "piston" effect. Earth is a solar-powered (lunar supplemented) engine. Continental coastline grinding is just one result of this daily mechanical-physical displacement.
With one difference: at the P-Tr boundary, we have that famous temperature and delta 13C spike. Imagine a lava flow getting too close to a methane clathrate deposit...
And then there's size. The Siberian traps are humongous.
However, the precise timing of the flood basalts compared to the boundary is still not clear, and there are two craters in Australia and Antarctica... the next couple of years should be interesting... Of course, utterly shaking up the sea is expected to release methane from clathrates, too.
Yes; the closer you get to India, the more turnover is there in the foraminifer fauna. I forgot how much of this is extinction, though.
in certain circumstances (eg. non-flight terrest./marine seasonal migration in mammals, floating fruit with edible nutritive pulp and indigestible seed in angiospermae)
These circumstances are very rare within those groups. Importantly, I can't see a shrew- or even badger-sized mammal migrating (there were no marine mammals in the Mesozoic). Besides, what do angiosperms and the K-Pg boundary have to do with each other?
Are/were there any primarily frugivorous marsupials?
There are some today, and probably there were more in the South American paleogene, but frugivorous mammals from the Mesozoic (why marsupials?) are unknown.
Perhaps this all relates to the earlier P-T extinction (or other), rather than the K-T extinction?
I don't understand. BTW, the Triassic is not T, but a T with a small capital R fused to it (so people write Tr if they can't do that); those abbreviations are standardized.
Interior heat diffuses equilaterally outwardly as a balanced continuous flow.
Wrong, it produces convection. Put a pot with water on your stove and watch. The heat comes from below, and it comes faster than the heat can diffuse. So the bottom layer of the liquid heats up, expands, and rises due to its lowered density. When it arrives at the top, it is pushed away by more rising liquid, cools down, becomes denser and sinks. In sum, thus, it moves in circles. The math has been done long ago, AFAIK, in case you don't trust your eyes.
Earth is a solar-powered (lunar supplemented) engine.
Io is (a Jupiter-powered one). The Earth is not; it's too big and too far away from the Sun, and the Moon is too small. The math has been done. On the other hand, Io would have cooled out long ago if it had to rely on radioactivity for its heat; it's small, so it has little radioactive material and a large surface-volume ratio. The Earth is the opposite case. Again, the math has been done. Stop trying to do science without math; it's a waste of time.
"Gravity is a force, not a property of a body."
AFAIK a body (aka density) can not exist without force (aka gravity). Have you heard of a body which has zero density or zero gravity?
One thing, 2 names. Synonymous.
"But surely you haven't missed the fact that nuclear fusion generates heat!?!"
Nuclear fusion can only occur in a body under super-high spherical compression AFAIK, IOW super-high density (= super-high gravity), heat is the equilaterally diffused* energy resulting from the form change of the bonds. [* diffused outwardly from center of highest compression]
As these bonds change form (physical structure gets crushed), electromagnetic energy is released (heat). Compression is limited to whole sphere crushing.
OTOH, nuclear fission can only occur in a body under super-high axial (equator-like) compression, the split of a sphere (atom), where the two halves of the former sphere immediately reduce their overall surface area forming to 2 smaller spheres (the most efficient form in nature), thus releasing extraneous bond energy (heat) during the transformation from asymmetrical 1/2 spheres to fully symmetrical spheres "instantly". In fission, compression is limited to a central axis (think of an axe splitting a ball of water).
Now, I have no idea if this is how physicists and mathematicians explain the processes, but I'd say that this is indeed how nature operates, and it provides a clue why sea turtle eggs must be spherical and common murre eggs can not be spherical, why spherical eggs are always laid in masses not singles and generally the more ovoid the egg shape the less eggs laid; and thus parallels the difference between meiosis and mitosis in reproduction and ontological development.
With an A in trigonometry at the Univ. Wisconsin, active membership in the Synergetics (Geodesic spatial geometry group) Yahoogroup, and the son of a math teacher, perhaps my understanding of math is sufficient? As a songwriter, I'm well aware of harmony and the math involved, but I never use a calculator or write algebraic equations to compose music or write lyrics. I've read countless math and physics texts.
As an aside, a sphere can be divided into 31 equilateral great circles, the human body has 31 spinal nerve pairs, and an octave can be split equally into 31 pleasing tones. That must be significant in physics-chemistry somehow, valence shells or something... Music of the spheres?
BTW, "Snowball Earth" never happened (over a long period), it couldn't and won't. Apparently, this has been confirmed recently.
"These circumstances are very rare within those groups. Importantly, I can't see a shrew- or even badger-sized mammal migrating (there were no marine mammals in the Mesozoic). Besides, what do angiosperms and the K-Pg boundary have to do with each other?"
I used those as modern examples (reindeer, grey whales, figs) as parallels with past events of evolutionary significance, since I'm not familiar with specific pre-pleistocene mammals and plants.
Live-birth marine reptiles may have migrated similarly to some modern cetaceans. Although I stressed the seasonal migration concept, the same advantages would apply to expansion of population boundaries IOW mobility at all stages of growth, not just at maturity, allowing a widespread population boom. Migrations include both long distances and very short jaunts (from swamp to adjacent hillside). I'm not sure about the K-Pg, but seed transport via mammal/avian allowed vast continents to be occupied very quickly. Crocs have gizzards and swallow pebbles to grind food. Ancient tetrapods ate the fat & protein-laden seeds (Pinus), using gizzards to wear off the shell, so plants evolved to increasingly toxify the seed coats. As part of this toxicant/biochemical/bitter (PTC) protection, outer rinds/skins rich in anti-microbial sugars and sugar-alcohols developed, which when consumed by tetrapods without gizzards allowed the skin to be digested but the coated seed to pass through the GI tract with the feces. Possibly the K-Pg (or other) extinction related to the change from seed eating with gizzards to fruit eating without gizzards.
Why then did eggs not become toxin-coated? Because the parents were mobile, unlike rooted plants, and so dispersed into various sites and niches, which no single predator type could dominate.
" Are/were there any primarily frugivorous marsupials?"
"There are some today, and probably there were more in the South American paleogene, but frugivorous mammals from the Mesozoic (why marsupials?) are unknown".
Seed eating must have been quite common in the Mesozoic, I assume the tetrapods with gizzards and grinding pebbles or grit, gulping not chewing with molars, while early mammals developed molars which enabled chewing of seeds (reducing the need for a gizzard) combined with bitter/PTC tasting tastebuds to avoid consuming seed toxins, allowing the mammalian GI tract to become less defense-oriented and more nutritionally efficient, allowing fat accumulation (inside bones?) and thus cool weather resistent oriented which then allowed mutations for fur (lanugo-type) to succeed.
Not sure about the non?frugivorous marsupials yet...
"Wrong, it produces convection."
Hmm, to me it is the same thing, heat goes out from center.
Will respond on this later. My point was that the energy flows outwards continuously, while sun/moon energy/gravity hits Earth's surface at each region discontinously but regularly on a clear cyclical pattern inducing tides like a Wankel engine or WW11 airplane engine.
DDeden (I may copy some of this post to my blog)
I think David meant to say fission rather than fusion. However AFAIK fission doesn't occur in the core, the heat generated is from normal radioactive decay releasing alpha and beta particles and heat. The processes involved in nuclear fission have no bearing on egg-shape. Breeding strategy and embryo morphology will affect this much more.
Convection is not a balanced continuous flow. Heat and matter rise together in columns spread out and as the matter cools it sinks. Its the principle that a radiator, a boiling kettle and the convection currents driving plate tectonics work on.
The tidal energy from the sun and moon are not nearly sufficient to influence the lithosphere. Earth is too large, the moon too small and the sun too far away to have this affect.
Io is very close to Jupiter and smaller than our moon. The nearest other bodies are all approaching the size of our moon and rather close.
You're understanding of maths may well be sufficient, but unless you actually do some to test you're suggestions they're not going to gain any support.
Do you have any references for the impossibility of "Snowball Earth"? The geological evidence indicates that at the very least a "Slushball Earth" did occur - probably more than once.
Thanks Dave, slightly different interpretations of nature I guess.
snowball earth
http://www.eurekalert.org/pub_releases/2007-03/icl-nep032307.php
http://news.bbc.co.uk/1/hi/scotland/1857545.stm
http://news.bbc.co.uk/2/hi/science/nature/159988.stm
http://www.aber.ac.uk/glaciology/epgr.htm
Form of simplest structure: tetrahedron
Form of most volume enclosed with least surface area: sphere
I think David meant to say fission rather than fusion.
No, no, I did mean fusion. You need a lot of energy to get fusion started, but once it gets started, it gives off a lot more energy than was necessary to start it. Take the experiment -- the hydrogen bomb: the ignition of a hydrogen bomb is a nuclear bomb, yet the hydrogen bomb is much more powerful than any nuclear bomb.
My mistake, apologies. I now see you were responding to DDeden's comments about equatorial planets influencing the position on convection currents in the sun- so of course you'd be talking about fusion. I thought that part of the discussion was still about the convection in the Earth's mantle - that'll teach me to read more carefully.
In my defense I was rather distracted by his link between nuclear fusion/fission and the shape of a turtle's egg. ;-)
(Why won't you use the <blockquote> tag? It makes everything much easier to read.)
Gravity is a force, not a property of a body.
Then let's stop talking about macroscopic bodies and instead let's talk about individual particles (like quarks). There are particles which lack mass (apart from kinetic energy), like photons. You are right that in order to get anything bigger than an individual particle, you need at least two particles and a force that binds them together -- but for most bodies that are in a serious gravity field, that force is not gravity. What keeps your computer from falling apart into its atoms? Electrostatic attraction.
heat is the equilaterally diffused* energy resulting from the form change of the bonds. [* diffused outwardly from center of highest compression]
Nope, it is not diffused. There is a lot of convection in the sun. Get an astronomy textbook (or a NASA website or anything).
As these bonds change form (physical structure gets crushed)
I don't think "crush" makes sense here...
OTOH, nuclear fission can only occur in a body under super-high axial (equator-like) compression, the split of a sphere (atom), where the two halves of the former sphere immediately reduce their overall surface area forming to 2 smaller spheres
This is wrong. Most atomic nuclei are not spheres; they occupy a wide range from cigar-shaped to disk-shaped. The sphere is a special case. Google for "double magic" (with the quotes).
Now, I have no idea if this is how physicists and mathematicians explain the processes,
Why don't you find out?
but I'd say that this is indeed how nature operates
Why do you bother idly speculating about something that has been being researched (with data) since long ago? Why don't you read what has been written on that topic and then build on that? You give me the impression that you have enough time to spend a few hours in Google.
and it provides a clue why sea turtle eggs must be spherical and common murre eggs can not be spherical, why spherical eggs are always laid in masses not singles and generally the more ovoid the egg shape the less eggs laid; and thus parallels the difference between meiosis and mitosis in reproduction and ontological development.
I don't understand how you arrive from spheres at the difference between meiosis and mitosis, or what you mean by "ontological development". Please explain.
BTW, do you consider 4 owl eggs, produced, shelled and laid once at a time, a "mass"? Oblong crocodile eggs are produced, shelled and laid all in one sitting.
With an A in trigonometry at the Univ. Wisconsin, active membership in the Synergetics (Geodesic spatial geometry group) Yahoogroup, and the son of a math teacher, perhaps my understanding of math is sufficient?
I do think it is. You just don't apply it, for some reason.
As a songwriter, I'm well aware of harmony and the math involved, but I never use a calculator or write algebraic equations to compose music or write lyrics.
See, that's the difference between science and art.
Not valence shells in any case.
More importantly, however, it looks like a logical fallacy. Lots of people believe that the human menstrual cycle is somehow coupled to the moon. They overlook two very important things: firstly, the 29-day duration of the menstrual cycle is an average of a range of several days, and secondly, the human menstrual cycle is just that -- human. Rats have a cycle of 11 days. Chimpanzees have one that is a bit longer than the human one. Why should of all mammals we be coupled to the moon? I think you have likewise merely found a coincidence. In keeping with this, not even all mammals have the same number of vertebrae and therefore spinal nerve pairs.
Where does this erratic jump in the topic come from? -- Anyway, a slushball earth (at least) was able to happen at the time in question, even though it can't happen anymore. The reason is that the Sun started out shining 30 % less strongly than today and has constantly increased in brightness (basic astrophysics). What do you mean by "long period"?
Here we have the problem. Why do you talk about things that you know full well you don't understand? Learn about them first, and then come back -- before then you won't know which parts of today's biosphere are parallels to past conditions and which are not.
Live-birth marine reptiles may have migrated similarly to some modern cetaceans. Although I stressed the seasonal migration concept, the same advantages would apply to expansion of population boundaries IOW mobility at all stages of growth, not just at maturity, allowing a widespread population boom.
I forgot about the pleurosaurs; the reproduction of the thalattosaurs, the placodonts, and the marine crocodiles is unknown -- but the others (ichthyosaurs, plesiosaurs and their relatives, mosasaurs and their relatives) all gave live birth, except (most likely) for the turtles.
I'm not sure about the K-Pg, but seed transport via mammal/avian allowed vast continents to be occupied very quickly.
No such thing changed across the K-Pg boundary.
Crocs have gizzards and swallow pebbles to grind food.
So do birds -- but not ornithischians, for example.
Ancient tetrapods ate the fat & protein-laden seeds (Pinus), using gizzards to wear off the shell, so plants evolved to increasingly toxify the seed coats.
Then why don't they all have toxic seed coats by now?
Possibly the K-Pg (or other) extinction related to the change from seed eating with gizzards to fruit eating without gizzards.
Why don't you look at the evidence first before you make your speculations public? I don't understand that.
No, there was no such change. Ornithopods had chewed for a long time before that, and so had the actual seed-eaters (multituberculate mammals and tritylodontid almost-mammals).
Doesn't the same apply to seeds? Especially flying seeds?
Seed eating must have been quite common in the Mesozoic
Indeed, multituberculates were as common as rodents are today; presumably for the same reason.
while early mammals developed molars which enabled chewing of seeds
Yes -- in the Middle Jurassic (multituberculates) respectively Late Triassic (tritylodontids, haramiyids).
allowing the mammalian GI tract to become less defense-oriented and more nutritionally efficient
Where does that leave the birds?
Wrong, it produces convection.
Will respond on this later. My point was that the energy flows outwards continuously
...while my point was that it doesn't. Convection is not continuous. Thanks, Namesake :-)
Again: all the knowledge you need is out there. Why don't you learn it?
I forgot... 31 pleasing tones? Can it get more subjective than that?
Not just among humans. Not all ears are human. Bird ears, for example, are quite different from mammal ears -- their high pitch limit is below the mammalian one (though above the one we humans actually reach), but they can discriminate more tones within the same frequency range. Pleasing or not, they'd vehemently disagree with "31".
As an aside, "WW11" is scary. Even in binary.
I've sent a post that hasn't shown up yet, maybe Darren needs to approve it? I'll wait a bit, can't remember all I said. I included links to the snowball earth hypothesis.
Somehow 1or 2 of my messages were not posted here yesterday, I don't know what happened, I thought it was because they hadn't yet been approved. Here's the snowball links:
"The sphere is a special case. Google for "double magic" (with the quotes)."
Google "double magic" results:
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I see nothing relevant. What was the point?
> like a Wankel engine or WW11 airplane engine.
WWII airplanes die use conventional piston engines or (late in the war) turbojets. The Wankel engine was invented in the fifties and not utilized before the mid-sixties.
> Is there evidence for any effect of the Deccan traps on any part of
the biosphere?
In India itself, I guess. The Indian fauna and flora must have suffered a lot. Otherwise we would have more "out of India" gondwanan immigrants than just a few frogs in Eurasia.
> As an aside, "WW11" is scary. Even in binary.
WWXI will be fought with RPGs, by infantry riding on the bed of Toyota pick-up trucks.No aircraft at all.
> (there were no marine mammals in the Mesozoic).
The Gondwanatheres are supposed to have originated in mangrove swamps, I think this is at least a marginally marine or coastal environment
By johannes (not verified) on 26 Mar 2007 #permalink
Regarding hearing, humming and spherical/planar/scalar harmony
Click on DDeden for information & reasonable speculation on mammal and human hearing and its relationship to ancestral human foraging.
A sphere can be divided into 31 equilateral great circles [circumscribed icosahedral geodesic sphere] associated with 12 vertexial nodes, the human body has 31 spinal nerve pairs associated with 12 cranial nerves, and an octave can be split equally into 31 pleasing tones and as well the 12 notes of the major scale.
A ref. to spinal/cranial nerves, please see this site.
"Lots of people believe that the human menstrual cycle is somehow coupled to the moon."
Yes, for good reason I'm sure. The vast majority of life on Earth dances to the solar-lunar-tidal cycle dance.
http://www.kingsoutdoorworld.com/hunting-guide/deer_activity.htm#BEST%20FISHING%20DAYS
Fishermen and hunters tend to follow the solunar cycles when crepuscularly active, whether or not they are actually at the tideline. Our ancestors were no doubt far more in tune with the lunar tidal flows than modern humans in urban areas are. While the women bled safely either at seashores or in caves (not moving around in the woods or the bush), the men would hunt and fish without distractions.
"They overlook two very important things: firstly, the 29-day duration of the menstrual cycle is an average of a range of several days, and secondly, the human menstrual cycle is just that -- human".
Apes also have similar estrus cycles, hylobats (gibbons, siamangs) (and possibly orangutans?) are quite close to humans cycles also, while chimps and gorillas have been away from the tidal effect due to being more inland, so their cycle has changed, becoming more terrestrial (monkey-like).
"Rats have a cycle of 11 days. Chimpanzees have one that is a bit longer than the human one. Why should of all mammals we be coupled to the moon?"
Both sun and moon. Our bodies' extra-cellular fluids have a salinity level of 9ppt, in between the Baltic sea and the Black sea, approximately estuarine, with pH level similar to seawater, we "are" the sea. However I can't answer your question without mentioning that our ancestors spent much time at the tidal shores foraging. If you picture our ancestors just swinging around and then dashing about on the splendid savannah with the little kitty cats, then I don't think you would be interested in my seashore speculations.
"I think you have likewise merely found a coincidence. In keeping with this, not even all mammals have the same number of vertebrae and therefore spinal nerve pairs".
The numbers 31 and 12 pop up together in "unexpected coincidental" correlations. If humans are the least derived physically, most derived mentally, from the primitive mammalian condition, then 12 and 31 might be of great significance. Need more data though. The Fibonacci sequence (seed grid on pinecones, pineappple skin) includes 5, 7, 12, 19, 31.
"I forgot... 31 pleasing tones? Can it get more subjective than that?"
Please see this article:
http://www.mooremusic.org.uk/kcm/et31.htm
"Not just among humans. Not all ears are human. Bird ears, for example, are quite different from mammal ears -- their high pitch limit is below the mammalian one (though above the one we humans actually reach), but they can discriminate more tones within the same frequency range. Pleasing or not, they'd vehemently disagree with "31"."
I'd assume that most insectivorous birds would have excellent pitch determination. Cave swifts use non-target echolocation. I don't know the specific jaw-ear configuration in birds, dino, pterasaurs, marine reptiles, would be interesting comparisons.
(ps: I've copied/edited parts to my blog at THE-ARC)
Johannes, I meant rotary-action engines, as opposed to a V8 or inline 4 cylinder engine.
I figure most tetrapods "originated" in mangrove swamps - estuaries, although turtles and monotremes seem to have bypassed the typical estuarine "portal" in some way, not sure how they became freshwater dwellers, possibly having developed on isolated mangrove-free islands at some stage (?).
> Johannes, I meant rotary-action engines, as opposed to a V8 or inline
4 cylinder engine.
A radial engine is not necessary a rotary engine. WW II radials were fixed to the plane, and did not rotate with the propeller, like the rotary in a WW I-vintage Sopwith Camel. The rotary engine as a concept in aviation was dead and gone by the mid twenties
>I figure most tetrapods "originated" in mangrove swamps
Early tetrapods like acanthostega were clearly freshwater dwellers.
There were no mangroves in the devonian, anyway.
Note: I made a transcription error regarding the Fibonacci series in my post to David M., ignore/delete that sentence, I've removed it from my blog.
That birds and mammals have different numbers of vertebrae and main nerves and may perceive sound differently than humans is expected, my interest in the 12-31 correlation/coincidence regarded the human condition, from the spheroid fertilized egg which splits into a nucleated cuboctahedral blastocyst and then transforms into hollow icosahedral spheroid form (31 great circles) and on into a 3 layered tube which eventually forms the 31 spinal vertebrae/nerve pairs; and that the fetus can likely hear and distinguish 31 distinct tones in an octave while in the womb, as likely can a newborn infant. The significance of this? Human language, it's relation to sound transmission and reception via bone conduction while submersed, and accompanying air conduction while above water. See Dive-Song link at the Deeper Blue link at my blog or at bottom of this message for more information as to why we don't talk like chimps.
http://the-arc.wikispaces.com/Dive+Song
Johannes, thanks,
rotary and radial engines both have pistons oriented in a circular path around a center, rather than on a inline plane or V position. There is a parallel in the spark-firing sequence around the radial-rotary engine center to the tropical sun-firing sequence around the rotating Earth center, with electromagnetic waves engaging the photosynthetic activators of the sunlit plants.
Regarding "mangrove swamp", formally this is both a botanical term and an ecological term, I meant it in the ecological sense, as in a tidal zone with ground-rooted woody plants Angiosperms, Palms, etc. which survive and reproduce in brackish or saltwater saturated soils. Mangrove swamp ecotypes may have no mangrove spp. A scientific paper was written on this subject, but I forgot the source.
I figure the early tetrapods must have dwelt and developed at the brackish tidal zone and estuaries for a long period, becoming more and more freshwater adapted, before stepping into the freshwater world. Mangrove swamps, embayments and estuaries were the tetrapodal portals of entry to the inland I guess, though no doubt other ways of entry were used by others (fish eggs stuck on pterosaurian feet transported to inland salt seas?).
Please excuse the length of this round-up reply.
Oops... stupid me. I hadn't googled myself. -- The hit with the nickel nucleus is relevant. Google again for "double magic" nucleus (with the quotation marks), and at least the first page of the 11,300 hits will be relevant. It's about certain combinations of proton and neutron numbers -- like the shell, the nucleus consists of orbitals, each of which has "space" for a certain number of protons and neutrons, and those in which all shells are full are "double magic".
However, even there the dinosaurs die out at the boundary, which (in at least one place) lies in the middle of a sediment layer that is sandwiched between two lava flows. (Eggshell fragments are very common there.)
Marine mammals in the Mesozoic
(there were no marine mammals in the Mesozoic).
The Gondwanatheres are supposed to have originated in mangrove swamps, I think this is at least a marginally marine or coastal environment.
Well, yeah, OK... :-)
Harmonies of harmonies
Why should I bother? I'm much less interested in the speculations themselves as in the evidence which can be used to test them.
31 or 42?
That's just a repetition from your previous post. Unless you believe that humans are somehow special, our 31 spinal nerves must be a mere coincidence, because most vertebrates have one of many other numbers. (BTW, your link doesn't work.) The 31 and 12 splits of the octave tell us something about our inner ears -- again they are a mere coincidence unless you believe that humans are somehow special.
That birds and mammals have different numbers of vertebrae and main nerves and may perceive sound differently than humans is expected
Just about every species of vertebrate has its own number of vertebrae and therefore spinal nerves. I know less about inner ears, but in any case birds and mammals have different ones, and other tetrapods have others yet again.
my interest in the 12-31 correlation/coincidence regarded the human condition, from the spheroid fertilized egg which splits into a nucleated cuboctahedral blastocyst and then transforms into hollow icosahedral spheroid form (31 great circles)
So far identical for all mammals (except I don't know about the monotremes).
and on into a 3 layered tube
Well, "tube"... rather "sheet". We form between the amnion and the (empty) yolk sac. Mammalian gastrulation looks quite stupid! :-)
and that the fetus can likely hear and distinguish 31 distinct tones in an octave while in the womb, as likely can a newborn infant.
How is that supposed to be different in other placentals?
The significance of this? Human language, it's relation to sound transmission and reception via bone conduction while submersed, and accompanying air conduction while above water.
Well, you made that up.
See Dive-Song link at the Deeper Blue link at my blog or at bottom of this message for more information as to why we don't talk like chimps.
I did. I conclude that you got the idea that human hearing has something to do with water, so you made up an elaborate scenario to explain that.
No, my friend, this is not science. Science is asking yourself "if I were wrong, how would I know". I'm not sure if your just-so story is testable -- if you would know if you were wrong.
Don't confuse the tides with bright full-moon nights.
Our ancestors were no doubt far more in tune with the lunar tidal flows than modern humans in urban areas are. While the women bled safely either at seashores or in caves (not moving around in the woods or the bush), the men would hunt and fish without distractions.
This is a just-so story. But nevertheless, the "seashores or caves" part is testable -- it doesn't work in a mammoth steppe, for example.
Why, BTW, would a seashore be safe? I'd imagine the opposite.
IIRC the chimpanzee cycle is 31 days, BTW... As long as you're talking about the moon, this is not "similar". It would mean that humans and chimps in the same place would menstruate together only once in 31 x 29 = 899 days = a bit over 2.46 years.
Our bodies' extra-cellular fluids have a salinity level of 9ppt, in between the Baltic sea and the Black sea, approximately estuarine, with pH level similar to seawater, we "are" the sea.
Yes, correct. And?
Come on. You didn't really believe the Moon's gravity cares for the chemical composition of a liquid, did you.
Erm... BTW... "ppt" means "parts per trillion". You were looking for "permil".
Ancient Man and the sea
If [...] then I don't think you would be interested in my seashore speculations.
If you have evidence to disprove the current textbook opinions, then I am interested. Even if you can explain all the evidence for the current textbook opinions without having any extra evidence to decide between them and yours, I am interested. If not, go back to work. :-)
Bird ears and the parochiality of 31
I'd assume that most insectivorous birds would have excellent pitch determination.
At least some have pitch determination that is more excellent than any mammal's, including ours.
Cave swifts use non-target echolocation.
(Has nothing to do with pitch distinction, AFAIK.)
I don't know the specific jaw-ear configuration in birds, dino, pter[o]saurs, marine reptiles, would be interesting comparisons.
I'm talking about the inner ear which doesn't fossilize. (The density of sound-sensitive cells in it, to be precise.)
The origin of Tetrapoda
I figure most tetrapods "originated" in mangrove swamps
Acanthostega, yes. Tulerpeton lived in the sea, and Ichthyostega apparently too.
There were coastal swamp forests, apparently. ("Mangrove" is a term for an ecosystem, not for a clade of trees.)
There were no angiosperms in the Devonian. The plant-life was dominated by club-mosses, tree-ferns and giant horsetails.
You may figure that early tetrapods would have lived at the brackish tidal zone, but you've given no evidence for this. What is stopping the fish already adapted to freshwater environments from evolving limbs (for improved locomotion in streams and lakes-not necessarily estuaries or "mangrove-like" environments).
While complex life almost certainly appeared in the sea it has had to undergo many important adaptations to live in freshwater, where there is a continuous flow of water into the organism which must be counterbalanced by pumping water out- otherwise (for animal cells at least) the cell will explode.
Just been catching up on the discussion and stopped half way along to interject to David M:
Snakes can't lick liquids from the ground, and they can't suck at all!
You should watch a snake drinking some time. In contrast to thin-lipped lizards and lipless crocs and birds which must scoop up liquid in the floor of the mouth or (in some lizards) lap with the tongue, snakes have fleshy lips (with labial glands and fat bodies) that make a good seal except for the notch (lingual fossa) in the rostral and/or mental scales. The fossa lets the tongue protrude from the closed mouth for vomerolfaction (if you watch carefully, the mental scale may rotate downward slightly with each tongue-flick), and also creates a narrow aperture through which the snake can suck liquid, sometimes with the head more or less immersed but even with the tip of the snout just touching the surface (I've seen this many, many times), or from droplets on leaves or the ground. The biomechanics of snake drinking is still pretty mysterious, but suction is definitely involved (see D. Cundall 2000, J Exp Biol. 203:2171-85).
This said, see de Queiroz and Rodriguez-Robles 2006 (http://www.unlv.edu/faculty/jrodriguez/33.pdf) for background on oophagy in snakes. AFAIK all egg-eating snakes ingest the egg whole before opening it in the oral cavity or oesophagus, or in some cases not at all (some snakes get temporary or even lethal blockage of the gut by whole lizard eggs, e.g. after eating gravid prey). But it's not implausible that snakes with blade-like teeth could open a soft-shelled egg and then suck out the contents, which could work even for eggs too large to ingest whole. I can't recall an example but it wouldn't be beyond belief, for me. Breaking a hard-shelled egg for the same purpose seems less likely, but not impossible. Of course constriction of the egg itself would be the wrong approach, but squeezing the egg against a sharp rock would work and might be an evolvable or inventable behaviour.
By John Scanlon (not verified) on 28 Mar 2007 #permalink
And trees like Archaeopteris. It didn't even have seeds, but you don't need an angiosperm or a seed plant in general for a mangrove.
Many Devonian and Carboniferous "freshwater" deposits have been reinterpreted as brackish or marine. Often the presence of tetrapods was the only "evidence" for freshwater, and that was based on the false premise that the lissamphibian intolerance for salt water is plesiomorphic for tetrapods.
However, the reason why we are less salty than the sea is different: when there are so many ions, nervous systems run into trouble, so the early gnathostomes replaced part of the salt with urea. Same osmotic pressure, fewer ions. This condition is kept by marine chondrichthyans and Latimeria. Freshwater and terrestrial gnathostomes have simply dropped the urea.
I have never seen a drinking snake, but I should have imagined that the lingual fossa makes suction possible. -- Is there a snake with blade-like teeth?
I figure the early tetrapods must have dwelt and developed at the brackish tidal zone and estuaries for a long period, becoming more and more freshwater adapted, before stepping into the freshwater world.
As mentioned, Acanthostega already lived in freshwater. The early tetrapods seem to have been euryhaline ( = able to live in a wide range of salt concentrations) -- there were marine temnospondyls in the Late Carboniferous (Iberospondylus) and throughout (most of?) the Triassic (Trematosauridae), for instance. Amniotes are still quite euryhaline: we humans can't drink seawater, but we can drink brackish water close to 2/3 as salty as (current) seawater, and the same holds at least for all other nonmarine mammals.
There is so much knowledge out there, and instead of learning it, you "figure" and "guess" based on your lack of knowledge... isn't it obvious that not much good can come out of this?
Incidentally, palms are angiosperms and appeared no earlier than the Late Cretaceous.
I've read there were angiosperms in the late Devonian, but can't think of the source, perhaps the same paper which discussed mangrove terminology.
I've read there were angiosperms in the late Devonian
You have misremembered. Perhaps you confused them with seed plants in general (Spermatophyta). Angiospermae is not known with certainty from before the Early Cretaceous, and possible older angiosperms don't get older than Late Triassic. That's 170 million years after the Late Devonian.
David M asked
Is there a snake with blade-like teeth?
There are lots. Actually the normal shape of a snake tooth is elliptical in cross-section only at the base, with two more or less sharp crests (typically a long anterolateral [mesiolabial] one and shorter posteromedial [distolingual]) that converge to make a blade-like tip. The sharpness and angle of convergence of the crests, and flatness of the other faces vary so the tip may be bluntly conical, stiletto-lke, spatulate or a sharp blade. There's an old paper by Scanlon and Shine on the web somewhere (or contact me for a better copy) that figures blade-like rear (pterygoid) teeth in lizard-egg-eating elapids. I also have a skull of Python reticulatus from Borneo where all the teeth are varanid-like, with sharp anterior and posterior blades, though this isn't typical for the species and may be a rare anomaly, but it does prove it's possible. Blade-like teeth near the front of the mouth would easily allow opening of soft-shelled eggs, but as I said last time I don't recall any species that uses this method (but note that it would be difficult to infer from preserved specimens, and like most snake behaviour very difficult to observe directly).
DM: "Most atomic nuclei are not spheres; they occupy a wide range from cigar-shaped to disk-shaped. The sphere is a special case."
DD: I've found nothing to substantiate your claim. Please provide a ref. (Of course during cleavage and the act of bonding, the shape alters from the normal spheroid.)
One source:
The liquid drop model is a model in nuclear physics which treats the nucleus as a drop of incompressible nuclear fluid, first proposed by George Gamow. The fluid is made of nucleons, and is held together by the strong nuclear force.
This is a crude model that does not explain all the properties of nuclei, but does explain the spherical shape of most nuclei.
It also helps to predict results in the field of nuclear fission by calculating the variation of binding energy necessary to change the shape of the drop, and then comparing it to the energy given by a neutron joining this nucleon. If it is sufficient, the drop "breaks" and this is called fission.
DM: Erm... BTW... "ppt" means "parts per trillion". You were looking for "permil".
Please substantiate your claim that "ppt" means "part per trillion".
From one source:
Salinity in the North Caspian varies markedly, from 0.1 parts per thousand (ppt) at the mouth of the Volga and Ural rivers to up to 10-11 ppt near the ...
soundscience.msrc.sunysb.edu/plankton/CaspianMethod.jsp - 7k - Cached - Similar pages
Agreed, Angiosperms appear to be after the Devonian (per 2 sites). I also neglected the role of insects regarding development of poisonous seed coatings (and the seeds themselves).
Posted by: David Marjanović | March 29, 2007 07:06 PM
The tiny inner ear cells in humans are hairs, derived from the anterior sensory hairs of the lateral line in fish. Yes, it has something to do with water, sound energy frequencies (vibrations) provide information about the environment, likely these hairs had once been external vibrissae for the crustacean-fish last common ancestor.
However, I was speaking of the middle ears, the little bones and eustachian tubes to the nasal cavity. A human non-scuba diver can submerge and allow seawater into the nasal cavity and middle ears (in order to avoid gas-equalization problems at depth), while the soft palate separates the nasal cavity from the oral cavity.
Notably sound is then magnified (increased sound conduction via bones and dissonance is reduced) at depth, as compared to having air filled middle ears, since there is electrolytic liquid in the inner ears, middle ears, and external ears. Thus humans retain a weak form of sonar capability, though far inferior to that of the specialized fish chasing dolphins.
Dive-Song is simply the brief description of the causative agent for many "special" traits of humans. White eyes (enlarged sclerae), monogamy, reduced size dimorphism compared to apes, singing, humming, clicking, music, epicanthal eyelids, primitive pinnae, unusual breathing adaptations, photic sneezing, eating raw shellfish, gift-giving-trade, sustained vocal communication, facial gestures, much reduced laryngeal air sacs compared to similar sized apes, etc. etc.
Speculative zoology? Yes, but strongly correlative biology and ecology and anthropology (when not dismissed by savanna-centered theorists). Does Dive-Song answer all the questions? No just a few of the hardest.
Savanna woodlands were occupied by humans much much later, after development of dug-out boats and tools allowed safe passage inland, previous to that trees and cliffs provided the only refuge from large predators, producing the arboreal apes. Tropical rainforests inland were obviously not where humans diverged from other apes.
DD: I used those as modern examples (reindeer, grey whales, figs) as parallels with past events of evolutionary significance, since I'm not familiar with specific pre-pleistocene mammals and plants.
MD: Here we have the problem. Why do you talk about things that you know full well you don't understand? Learn about them first, and then come back -- before then you won't know which parts of today's biosphere are parallels to past conditions and which are not.
DD: Point taken, I doubt I have much time to dig so deeply and thoroughly. However, life today does not differ very much from life 20 or 200 million years ago, if one understands natural selection, which I do, and one has good data on climate-environmental changes which I don't.
(My "I see" comment refers to my underappreciation of the diversity of snake tooth shapes.)
Don't you read anything about chemistry, including reports of pollution? Google for "parts per trillion", and you'll see... percent, permil, ppm, ppb, ppt, ppq. I have seen "ppt" used for "parts per thousand", but that's a rare mistake.
DD: I've found nothing to substantiate your claim. Please provide a ref.
Sorry, it was in a Scientific American special volume that I read long ago. But what results did you get from googling for "double magic" nucleus? Does none of them help?
The tiny inner ear cells in humans are hairs, derived from the anterior sensory hairs of the lateral line in fish.
They are not hairs, they are cilia (and thus outgrowths of cells, not that it matters here). Cilia occur in lots of sense organs, like vertebrate eyes and the lateral line organ, so you're right that the inner ear and the lateral line organ are on some level the same, "fish" have their own inner ears. We're talking about vertebrate inner ears, not human inner ears which are in no way special.
likely these hairs had once been external vibrissae for the crustacean-fish last common ancestor.
No, that common ancestor had cilia all over its skin and used them for locomotion (in addition to having specialized cilia in certain sense organs, e.g. one kind of eye). Flatworms, nemertines and several other clades still move that way most of the time (like Paramecium).
Notably sound is then magnified (increased sound conduction via bones and dissonance is reduced) at depth, as compared to having air filled middle ears, since there is electrolytic liquid in the inner ears, middle ears, and external ears.
Thus humans retain a weak form of sonar capability
Hearing in water is not the same as sonar, just like hearing in air is not the same as sonar -- bats have sonar, we don't.
The soft palate is common to all mammals.
Fine, but it's still a just-so story. It doesn't explain anything that can't be explained otherwise. (Except maybe for the sclerae -- can you direct me to more info about those? What are epicanthal eyelids, and what do you mean by pinnae -- certainly not the external ears?) Let me try:
- We are, on average, not monogamous. We fuck around almost like bonobos.
- Reduced size dimorphism comes with reduced male-male competition, as do the shrunken canines and the absence of large laryngeal air sacs. Make love, not war... see above.
- Music including singing and humming can be explained in lots of other ways that don't necessitate regular diving. Try communication. Anything can come out of a brain as bloated as ours.
- Clicking? Do you mean click consonants?
-- These have probably developed from consonant clusters. Plenty of languages in West Africa today have coarticulated kp and/or gb, that is, you put the tongue against the velum, close the lips, and then open both closures at almost the same time. Try pronouncing that. More often than not you'll open the lips just before instead of just after the velar closure. Voilà, the bilabial click. link
-- The idea that the last common ancestor of all extant languages contained click consonants comes from the idea that the Khoisan languages are the sister-group to all the rest. Even if that is true, and even if the presence of clicks in all Khoisan languages is retained (plesiomorphic) instead of an innovation (autapomorphic), clicks can still have arisen in the MRCA of all extant languages as described above. Keep in mind that there's no evidence that the MRCA of all extant languages was the first language; most likely, it was spoken long after the first language.
- What do you mean by "unusual breathing adaptations", and how many of these have been tested in other mammals, especially other apes? It is indeed interesting that our heart rate drops when we dive -- but we don't know if the same happens to a chimp, because chimps don't dive. Maybe we could convince an orang-utan to do it; they do go quite deep into water if they need to.
- "Photic sneezing" means having to sneeze when looking into the sun, right? I don't have that, and I don't think it's widespread, so I don't think it's likely that any population of our ancestors all had it. On the other hand, how widespread is it beyond humans? Do any chimps have it?
- We are the only apes that ever get a chance to eat raw shellfish. You don't know if there's any "special trait of humans" involved here; as long as you don't, you can't hope to explain anything about it.
- Gifts are widespread among mammals and birds. Trade and communication come with a bloated brain -- and how other than vocal would you communicate? Constantly having to look at each other is a disadvantage. I'm trying to say "sustained vocal communication" doesn't need an explanation at all.
- Facial gestures are normal for Old World monkeys at the least. Nothing to explain here.
Savanna woodlands were occupied by humans much much later, after development of dug-out boats and tools allowed safe passage inland,
Then why do we find their remains long, long before any kind of boat?
previous to that trees and cliffs provided the only refuge from large predators, producing the arboreal apes.
Arboreality is the normal state for primates; it does not need to be explained. You are right that the loss of arboreality needs to be explained -- and that happened twice, because 5 % of all surviving chimps live in the savanna. Predators are not much of a concern for a group of chimps; they are famous for putting up a fight, with weapons.
Tropical rainforests inland were obviously not where humans diverged from other apes.
The oldest human remains do not come from outright rainforests, but still from wooded environments with a more or less closed canopy. The savanna came later, when the forest shrunk.
Point taken, I doubt I have much time to dig so deeply and thoroughly.
As long as you don't do that, you're wasting what time you have by idle, uninformed speculation, reinventing the wheel at best. You have your priorities backward. First learn, then draw your conclusions from what you have learned. How much time do you spend writing your blog? Spend that time in Google instead (or in libraries, of course). Then come back, and we can discuss, as opposed to me simply shooting down one speculation after the other because it has already been falsified or tries to explain phenomena that don't need explanations.
DM: I did [look at the Dive Song brief]. I conclude that you got the idea that human hearing has something to do with water, so you made up an elaborate scenario to explain that.
Nope. I just connected the facts in the most parsimonious manner. And that my friend is Science.
> I forgot to mention: you can't eat the eggs of a mosasaur or
plesiosaur any more than those of a stagodontid or "pediomyid"
metatherian.
On the effect of the K/Pg extinction on stagodontids:
It might be wishful thinking on my side - I happen to like stagodontids - but doesn`t Eobrasilia look like a post-K/Pg (Itaboraian) survivor?
Marshal (Journal of Paleontology, Vol 58, No 1; Jan. 1984; pp. 173-177)
seems to come to the same conclusion.
DM: "Don't you read anything about chemistry, .."
DM: "Most atomic nuclei are not spheres; they occupy a wide range from cigar-shaped to disk-shaped."
DM: "it was in a Scientific American special volume that I read long ago."
DD: 1) Yes. 2) False. 3) False. One must study and understand the primacy of the spherical shape in nature before one can speak intelligibly about egg shapes, planets, nuclear fission-fusion, meiosis-mitosis, gravity-density, diffusion-radiation, conduction-convection, erosion-deposition, estrus-menstrual cycles, etc. Else it is just blowing hot air.
By DDeden (not verified) on 01 Apr 2007 #permalink
Nope. I just connected the facts in the most parsimonious manner.
It's not the most parsimonious possibility -- the whole diving stuff is not needed to explain the features you mentioned. It is an unnecessary ad hoc assumption.
Interesting point on Eobrasilia. However, 1984 was a long time ago. The only more recent assessment of its phylogenetic position (within the first page of Google results anyway) is on this page which cites its sources. Even if it is a stagodontid, it's on the wrong continent -- we'd still have complete extinction of Stagodontidae in North America, the only difference is that we'd have to assume that a stagodontid managed to get to South America and then survived the K-Pg boundary there.
2) False. 3) False.
2) Evidence, please. 3) How do you know? Have you read all of them?
One must study and understand the primacy of the spherical shape in nature before one can speak intelligibly about [...]
First, one must find out whether there is, in a meaningful way, such a thing as "the primacy of the spherical shape in nature". You assume a priori that there's a common underlying reason for all spheres, even if this necessitates introducing an ad hoc assumption. What if one sphere has nothing to do with another?
And no, spheres have zero to do with meiosis, mitosis, gravity, density, or menstruation. If you have evidence to the contrary, please tell me.
By David Marjanović (not verified) on 01 Apr 2007 #permalink
Just want to make an appearance here and point out that this post now has a record 85 comments.
By tetrapodzoology on 01 Apr 2007 #permalink
Congratulations! You're reaching the average thread length of Pharyngula! :-)
"spherical shape of most nuclei" as I referenced earlier, do you dispute that? Even simple nuclei tend toward sphericity, although they don't resemble perfect spheres due to having only a small quantity of neutrons and protons. Eg. a nucleus of 2 P and 2 N might appear tetrahedral, but are the most spherically possible shape when Nucleons = 4.
Anything which places ancient human ancestors 7-1ma long distances away from the shores (previous to boats) adds complexity (abundant sweating = needs abundant salt + water, freshwater not enough).
85 comments (+1).
We just had a computer crash, I think I sent a comment just now, but not sure if it posted. To avoid repeating, here's an online text helpful in comprehending the properties of common sphericity in nature, by the inventor of the geodesic dome.
http://www.rwgrayprojects.com/synergetics/synergetics.html
DM: Hearing in water is not the same as sonar, just like hearing in air is not the same as sonar -- bats have sonar, we don't.
DD: False. Sonar uses echoes (water or air), aka blind person with cane or oral clicking. Google.
DD: Dive-Song is simply the brief description of ...
DM: Fine, but it's still a just-so story. It doesn't explain anything that can't be explained otherwise.
DD: It explains them most parsimoniously, these functions all worked together and were selected for.
DM: (Except maybe for the sclerae -- can you direct me to more info about those? What are epicanthal eyelids, and what do you mean by pinnae -- certainly not the external ears?) Let me try:
DD: Jane Goodall found 1 chimp with white sclerae, and the albino gorilla Snowflake had white sclerae, all other apes & monkeys (and nearly all mammals) do not have exposed/enlarged white sclerae. All humans do, although Central Africans have a yellowish tint. Why? It fits perfectly into a diving scenario for our ancestors. As well the epicanthic (slant) eyelids of the Khoisan, some Nubian and Middle Eastern and East Asian people, and the previous reduction and subsequent enlargement of the pinnae and poor ear muscular control compared to typical arboreal and savanna spp.
DM: We are, on average, not monogamous. We fuck around almost like bonobos.
DD: We (viewed as all age, not just young adult) are far more monogamous than any great ape.
DM: Reduced size dimorphism comes with reduced male-male competition, as do the shrunken canines and the absence of large laryngeal air sacs. Make love, not war... see above.
DD: Is this found in any typical savanna or arboreal spp.?
Savanna chimps tend to be more dimorphic (and less bipedal) than rainforest bonobos. Since you have stated human ancestors were on the savannas, how do you resolve this?
It would however be expected to occur if the male & female (with infant) dove together alternatively, changing from direct male-male competition to male/female-male/female, something which could not occur terrestrially but could occur at the shores and arboreally (see partial parallel in gibbons re. air sacs).
DM: Music including singing and humming can be explained in lots of other ways that don't necessitate regular diving. Try communication. Anything can come out of a brain as bloated as ours.
DD: What savanna/woodland mammals sing or hum? Notably, arboreal songbirds sing, ground birds don't. Presuming our ancestors were terrestrial, what indicates that they would sing and hum? Why would they alter from a loud long call to a continuous vocalizing pattern? Mice have proportionately larger brains than humans, and they sing and live on savannas, is that the only comparison?
DM: Clicking? Do you mean click consonants?
-- These have probably developed from consonant clusters.
DD: Clicks as you noted. Ancient, unknown date of origin, possibly derived from breath holding mannerisms.
DM: What do you mean by "unusual breathing adaptations", and how many of these have been tested in other mammals, especially other apes? It is indeed interesting that our heart rate drops when we dive -- but we don't know if the same happens to a chimp, because chimps don't dive. Maybe we could convince an orang-utan to do it; they do go quite deep into water if they need to.
DD: Although uncertain, I'd guess any great ape immersed would fill their laryngeal air sac with exhaled air and could not dive.
DM: "Photic sneezing" means having to sneeze when looking into the sun, right? I don't have that, and I don't think it's widespread, so I don't think it's likely that any population of our ancestors all had it. On the other hand, how widespread is it beyond humans? Do any chimps have it?
Darwin found no sun-frown and assumably no sun-sneeze when he tested a young chimp and orang from very dark to bright light conditions. Uniquely human AFAIK, but likely similar to marine iguanas which look at the sun and sneeze to remove salt brine from nasal glands (they dive and eat salty seaweed). The photic sneeze exhales old air from the body entirely at roughly the same speed as a dolphin ventilatory cycle, far faster than a normal aerobic exhale in a human.
DM: We are the only apes that ever get a chance to eat raw shellfish. You don't know if there's any "special trait of humans" involved here; as long as you don't, you can't hope to explain anything about it.
DD: Chimps eat freshwater shrimp larvae in inland non-tidal streams underneath leaves. No apes live on tidal waters, apes developed their derivations (eg. longer fingers) as they moved from the coasts inland.
DM: Gifts are widespread among mammals and birds. Trade and communication come with a bloated brain -- and how other than vocal would you communicate?
DD: Savanna animals typically use scent and visual, vocal is usually danger-related. Mammalian gift-giving not so common (exc. chimp male exchange food for sex with older females)
DM: Constantly having to look at each other is a disadvantage. I'm trying to say "sustained vocal communication" doesn't need an explanation at all.
DD: How many inland wooded savanna spp. have sustained vocal communication?
DD: Savanna woodlands were occupied by humans much much later, after development of dug-out boats and tools allowed safe passage inland,
DM: Then why do we find their remains long, long before any kind of boat?
DD: Butted hand axe/adze remnants (Eritrea reef 125,000yrs) indicate possible dug-out contsruction. Boats rot quickly, bones less so, teeth less so. There were certainly hominids inland with at least partial arboreal adaptations, but our ancestors were generally along coasts and near-shore isles.
No doubt however there was indeed some mixing, simply due to the long periods involved.
DD: previous to that trees and cliffs provided the only refuge from large predators, producing the arboreal apes.
DM: Arboreality is the normal state for primates; it does not need to be explained. You are right that the loss of arboreality needs to be explained -- and that happened twice, because 5 % of all surviving chimps live in the savanna. Predators are not much of a concern for a group of chimps; they are famous for putting up a fight, with weapons.
DD: Fight against a small leopard perhaps, no chance against a lion, dead meat. That's why savanna chimps stay near trees, and why our ancestors avoided that whole scene until they came upstream on boats.
DM: The oldest human remains do not come from outright rainforests, but still from wooded environments with a more or less closed canopy. The savanna came later, when the forest shrunk.
DD: The further away from seashores/isles, no matter what eco-type, the less likely a non-tree-sleeper would survive, until dug-outs (and fire?), due to the big cats. Human ancestors lost their tree gripping feet a long time ago, and consider the pregnant females & chubby infants, very unlike the lightning fast quadruped baboons and patas monkeys.
I considder it most likely that at different periods, our ancestors were islanded but sometimes able to travel to coastal shores, with variable results (like sea turtles and croc populations, unlike inland theropods or sauropods). They weren't absolutely island isolates.
Gosh, enough already!
Coastal lagoons home for Texas primates 42ma: Expected per ARC Theory, Estuarboreal Anthropoids Hypothesis.
(hopefully one of these links will work)
"DD: Fight against a small leopard perhaps, no chance against a lion, dead meat. That's why savanna chimps stay near trees, and why our ancestors avoided that whole scene until they came upstream on boats."
delurking here for a minute.
Savanna chimps are almost never killed and eaten by lions,leopards, etc, they are scavenged instead.
By Raymond (not verified) on 03 Apr 2007 #permalink
"spherical shape of most nuclei" as I referenced earlier, do you dispute that?
Yes. http://en.wikipedia.org/wiki/Atomic_nucleus#Modern_nuclear_physics
This article http://en.wikipedia.org/wiki/Unbinilium mentions the "spherical model of shell formation". If you like, I can try to dig up the reference it cites.
From what I remember to have read, you will not be surprised that the spherical nuclei are the most stable ones, that the nuclei with the most extreme cigar or disk shapes are radioactive with very short half-lives, and that radioactive decay always turns less spherical into more spherical nuclei.
(He-4 is double-magic and therefore predicted to be spherical. But of course the tetrahedron is the only three-dimensionally symmetrical way to pack four objects of about the same size, so the fact that the He-4 nucleus is as spherical as it can be doesn't mean much.)
here's an online text helpful in comprehending the properties of common sphericity in nature
Stop being metaphysical already. Both double-magic nuclei and sauropod eggs are spherical, but not for the same reason: the latter probably for efficiency, the former because of the strong nuclear force and Pauli's exclusion principle.
Neither tarsiers nor omomyids are anthropoids.
Perhaps more importantly, finding dead primates in a lagoon does not mean there ever were living ones in a lagoon. Think of the proboscis monkey (http://en.wikipedia.org/wiki/Proboscis_Monkey) which lives in mangrove forests.
Do you explain your "theory" (hypothesis) anywhere? I don't seem to have understood it.
DM: Neither tarsiers nor omomyids are anthropoids.
DD: Right, the tarsier, anthropoid LCA may have been a coast dweller, possibly derived from the earlier nocturnal lemur ancestors. Some the Indrids were semi-aquatic and large AFAIK, without large predators (presuming an island) some may have become diurnal (losing the tapeta lucida) and partly tidal (reduced olfaction? shorter snout) which became the root for the later anthropoids. The large eyes of the tarsier may have been a later adaptation for a return to nocturnlity after returning to inland area with predators (continental Africa)
DM: Perhaps more importantly, finding dead primates in a lagoon does not mean there ever were living ones in a lagoon. Think of the proboscis monkey (http://en.wikipedia.org/wiki/Proboscis_Monkey) which lives in mangrove forests.
DD: yes, washed downstream and left in a lagoon is quite possible. I figure they were affected by the tide in some manner, though they may not have swum in the lagoon itself. It is much less likely that they lived very far upstream from the tidal effects, since the teeth are much denser than water and would sink once the body decomposed if not eaten and would be eroded by the current when tumbling downstream and again at the tidal shore.
Working on it, the "Estuarboreal Anthropoids Hypothesis". Coastal primates survived during inland droughts, refilled the interior many times (lemurs, tarsiers, Miocene apes, monkeys, hominids, Homo, humans) due to time on off-shore isles free from large predators.
DM: Yes.
DD: ?? (flabbergasted)
DM: Stop being metaphysical already. Both double-magic nuclei and sauropod eggs are spherical, but not for the same reason: the latter probably for efficiency, the former because of the strong nuclear force and Pauli's exclusion principle.
Sphericity exists as a standard form in matter and energy, often repeating as frequencies. This is not hyperbole or metaphysics AFAIK.
It's just how nature operates in fluids (air, water, plasma, magma) in 3 dimensions (or 4+). Solid shells are crystaline, but they too display frequencies as they move from center.
Somebody want to throw in their 2 cents to clarify?
DD: "Nuclei tend to be sphere-like not oblong or ovoid"
Posted by: Raymond
Raymond, any idea why not?
Chimps can have a long life cycle, and bear few young which develop slowly, so obviously no predator can specialize on chimp eating without destroying the chimp population.
Beyond that and the agility of chimps scampering up trees, I can't see why they would not be an easy meal for savanna predators.
No predator needs to specialize on chimps in order to be able to kill any. Leopards do sometimes succeed, for example.
The reason is that they live in groups and fight back. They do the human thing, in short.
the tarsier, anthropoid LCA may have been a coast dweller, possibly derived from the earlier nocturnal lemur ancestors.
"May have been"? You're pulling this out of thin air. It can't be completely ruled out at the moment, but it's not parsimonious at all -- all known close relatives of that ancestor were arboreal.
Some the Indrids were semi-aquatic and large AFAIK
I've never heard of any semiaquatic ones, but even if, they don't matter for anthropoid ancestry -- they are very young and restricted to Madagascar, and even farther away from Anthropoidea than the tarsiers are.
without large predators (presuming an island) some may have become diurnal (losing the tapeta lucida) and partly tidal (reduced olfaction? shorter snout)
There are more parsimonious explanations for both of these developments. Namely, there are few to no large arboreal predators, and an arboreal frugivore benefits more from sight (and thus from being diurnal) than from olfaction.
The large eyes of the tarsier may have been a later adaptation for a return to nocturnlity after returning to inland area with predators (continental Africa)
Why aren't they simply retentions, exaggerated by the fact that small animals always have relatively larger eyes at the same visual acuity? BTW, there are no tarsiers in Africa, and AFAIK there have never been. Primates as a whole is primarily a northern-hemisphere phenomenon.
yes, washed downstream and left in a lagoon is quite possible.
Indeed, but that's not even what I mean -- I meant living right next to/above the lagoon, in a mangrove forest.
I figure they were affected by the tide in some manner,
Working on it, the "Estuarboreal Anthropoids Hypothesis". Coastal primates survived during inland droughts
Why? Coasts are not necessarily wet, at least not with freshwater. Some coasts are deserts; some deserts (notably the Atacama and the Namib) consist only of coasts. -- More importantly, you'll have to find suitable drought events in the fossil record. I don't think you'll find any.
refilled the interior many times (lemurs, tarsiers, Miocene apes, monkeys, hominids, Homo, humans) due to time on off-shore isles free from large predators.
So far it sounds like the opposite of parsimony.
"Standard form" doesn't mean anything. If there are forces that pull stuff into a spherical form, it will assume a spherical form. If not, it won't. If there are both forces that pull it into a spherical form and forces that favor other forms, a compromise will result.
"Nuclei tend to be sphere-like not oblong or ovoid"
I agree with sphere-like; most nuclei are reasonably close to a sphere. However, only the doubly magic ones are really spherical; all others are off, being longer or shorter along one coordinate axis than along the other two.
(BTW, it doesn't make much sense to call a nucleus fluid, solid, or anything. Quantum uncertainty makes all of that meaningless at these small scales.)
DD: False. Sonar uses echoes (water or air)
I can only repeat: hearing in water is not the same as sonar.
aka blind person with cane or oral clicking. Google.
What should I google for?
You have to introduce an extra assumption; that makes it less parsimonious.
DD: Jane Goodall found 1 chimp with white sclerae, and the albino gorilla Snowflake had white sclerae, all other apes & monkeys (and nearly all mammals) do not have exposed/enlarged white sclerae. All humans do, although Central Africans have a yellowish tint. Why? It fits perfectly into a diving scenario for our ancestors.
As well the epicanthic (slant) eyelids of the Khoisan, some Nubian and Middle Eastern and East Asian people,
Are you sure that adaptations to cold (the usual explanation), random drift, and sexual selection are all less parsimonious?
and the previous reduction and subsequent enlargement of the pinnae
What makes you think this happened?
and poor ear muscular control compared to typical arboreal and savanna spp.
Well, we aren't typical. We are rather unique among mammals in relying so much on eyesight.
DD: We [...] are far more monogamous than any great ape.
OK, but why, then, are the gibbons really monogamous?
Why should it be, or why not?
Savanna chimps tend to be more dimorphic (and less bipedal) than rainforest bonobos.
How about rainforest chimps?
Since you have stated human ancestors were on the savannas, how do you resolve this?
I still don't see a problem in the first place. (However, the term "savanna" doesn't make sense for the habitat of our ancestors before something like 2.5 Ma ago.)
DD: What savanna/woodland mammals sing or hum?
Why should this matter? Why do we need a precedent? As long as you can't show that music is an outright disadvantage in a savanna (let alone a more heavily forested environment), you don't have a point.
Notably, arboreal songbirds sing, ground birds don't.
Only one clade of songbirds (a subset of Passerida) sings at all, and that clade has very few if any terrestrial representatives, AFAIK.
Presuming our ancestors were terrestrial, what indicates that they would sing and hum?
What indicates they wouldn't? On the other hand, what indicates they would before having developed language?
Why would they alter from a loud long call to a continuous vocalizing pattern?
To pack more information into it? As in, speaking?
Mice have proportionately larger brains than humans, and they sing and live on savannas, is that the only comparison?
Is that the only counterexample to your speculation, you mean!
Ancient? Yes, going back at least to the MRCA of the Khoisan languages. But that's it, probably.
Breath-holding mannerisms? Please explain. Holding your breath is closing the glottis, not putting the tongue against the velum. The latter prevents air flow through the mouth, but not through the nose; say "ng", and you'll see I'm right. (Indeed, all languages that have clicks have nasal clicks, during which air escapes through the nose.)
1. Why?
2. Which apes actually have a laryngeal air sac? All except us?
Darwin found no sun-frown and assumably no sun-sneeze when he tested a young chimp and orang from very dark to bright light conditions.
One chimp and one orang-utan! What a compelling sample.
Uniquely human AFAIK
No, much worse: unique to a few humans. I don't have it and I don't know of anyone who has it.
but likely similar to marine iguanas which look at the sun and sneeze to remove salt brine from nasal glands (they dive and eat salty seaweed).
But surely you have noticed that we don't have any salt glands whatsoever, which makes sneezing entirely useless in getting rid of salt? While I am at it, what does the sun have to do with all that? Why don't the marine iguanas simply sneeze after every dive? Or do they?
The photic sneeze exhales old air from the body entirely at roughly the same speed as a dolphin ventilatory cycle, far faster than a normal aerobic exhale in a human.
(If we do that too often, our blood becomes basic, and we run into serious trouble...)
No apes live on tidal waters
apes developed their derivations (eg. longer fingers) as they moved from the coasts inland.
No, we shortened ours when we stopped climbing every day.
DD: Savanna animals typically use scent and visual, vocal is usually danger-related.
So what? We have an arboreal frugivorous past, not a terrestrial grass-eating one.
Mammalian gift-giving not so common
Still not surprising.
And don't forget the many marine mammals that don't communicate much at all.
DD: Butted hand axe/adze remnants (Eritrea reef 125,000yrs) indicate possible dug-out contsruction.
A quarter of a million years ago is not "long before any kind of boat". I was talking about the several million years of human prehistory in South Africa, Chad, and so on.
but our ancestors were generally along coasts and near-shore isles.
You state this as if it were a fact, but it is an inference from your hypothesis. Make sure not to confuse those two and not to make others confuse them.
DD: Fight against a small leopard perhaps
Not "perhaps".
no chance against a lion, dead meat.
If it's just one lion... Aren't lions more interested in bigger prey in the first place?
That's why savanna chimps stay near trees, and why our ancestors
apparently did exactly the same, judging from the remaining climbing adaptations all over Australopithecus. Our ancestors did not stay away from the scene; we have found their bones in the scene.
DD: The further away from seashores/isles, no matter what eco-type, the less likely a non-tree-sleeper would survive
It looks like our ancestors kept sleeping in trees before they became Homo.
Why? :-)
David M.: I have the "sun-sneeze" reflex. Sometimes. Its entirely unpredictable when it happens, though it might be to do with the length of time I've been indoors.
A google for "Sonar in Humans" produces this result, the abstract for a Harvard undergraduate thesis. Blind (and blindfolded) people appear to be able to detect the presence of an object by listening for echoes. They aren't very good at the "these are small, but those are far away" problem. So under specific circumstances of sensory deprivation humans can use echoes to detect the presence of an object. The difference between this and sonar is a gaping chasm.
I suspect from the avaliable evidence that tarsiers did go through a diurnal phase. Tarsiers are unusual in being nocturnal animals that primarily use sight, and do not possess a tapetum lucidum. Many primairly diurnal animals (other anthropoids for instance) have lost the tapetum lucidum. The only other nocturnal anthropoid (the Owl Monkey) also lacks the tapetum. Additionally, Tarsiers also have the same colour vision as in many New World Monkeys- something you might well see if they had a diurnal ancestor.
Having said that, there's no need to postulate aquatic ancestors of any kind, and I agree with pretty much everything else in your comments.
DDeden: It seems you are taking the theory that modern coast-dwelling humans left Africa by spreading along the coastline and applying it to situations where it doesn't work. While the coast-hugging model fits with the currently avaliable evidence I can't help feeling that at the same time other groups living inland wandered out over the Sinai peninsular without ever seeing the sea.
By Dave Godfrey (not verified) on 05 Apr 2007 #permalink
"Raymond, any idea why not?
Beyond that and the agility of chimps scampering up trees, I can't see why they would not be an easy meal for savanna predators."
I have no quarrel with you over your supposition that ancient savannah hominids were devoured by a great variety of predators.Indeed, every life stage of *Australopithicus* and *Paranthopithicus* has detailed fossil remains which show predation from everything from eagles,cats,hyeanas and dogs.
Modern chimpanzees cannot be compared to these hominids, for one thing, they are far more powerful and as you've stated, they're intelligent enough to remain within woodlands to easily escape up trees.The few skeletal remains of dead adult chimps found in predator heavy areas are almost always scavenged after death from intraspecies affairs or disease.Nevertheless, lion/adult chimp interactions do occur.Many native witnesses have seen first-hand such encounters.
Let me put it this way, there is a reason why the Bili Ape is known as the "Lion-killer" among the local peoples who live near them.
Important things to understand about chimp strength, lacking claws and most of their teeth, a pair of male chimps ripped the buttocks,genitals,fingers etc of a man and severely muitilated his wife.The reason?They didn't
get any birthday cake.A wild chimpanzee can strangle,dislocate,rip off and batter any potential predator and that's before they consider sticks and stones.
Make no mistake, Chimpanzees are _very_ dangerous.
I suspect from the avaliable evidence that tarsiers did go through a diurnal phase. Tarsiers are unusual in being nocturnal animals that primarily use sight, and do not possess a tapetum lucidum.
Oh. OK.
I can't help feeling that at the same time other groups living inland wandered out over the Sinai peninsular without ever seeing the sea.
Maybe not at the same time -- it was just desert --, but certainly all earlier human migrations took that route.
The sphere in nature:
least surface area, maximal surface tension in equilibrium, maximal bond quantity of enclosed sub-units ie nucleons.
In a body full of sub-units, for each sub-unit (eg. nucleons) to have the maximum number of bonds (contact points), the body must be spherical, any other form will result in fewer contact points in sum.
If the sub-units have weak bonds, the sphere allows the most secure body, simply due to the higher number of contact points per sub-unit. A sphere of weakly bonded sub-units may be stronger than a non-sphere with strongly bonded sub-units.
So regarding the nucleus, if double magic, the body is spherical with maximized contact points.
If regarding the nucleus, if not magic, the body will compact towards a sphere-like condition in order to maximize bonds.
The exception occurs when the nucleus is double magic plus one extra nucleon, in which the extra nucleon has the least number of contact points, and so protrudes from the sphere. For every additional nucleon added, the sum of contact points is greater, so it tends toward greater sphericity.
This implies that a normal nucleus is never cigar-shaped (except when the sum of nucleons = 2) or disk shaped (except when the sum of nucleons = 3), but instead, the nucleus is always spheroidal except during fusion or fission.
The neutrons act as buffers between the protons allowing this tight spherical fit. If the number of neutrons is less than protons, then the protons can't seat properly into the sphere shell, and will stay on the shell surface (reducing sphericity of the body) reducing the body density and thus the perceived gravity.
If one has a double magic nucleus, remove one proton and replace with a neutron, almost no effect.
If one has a double magic nucleus, remove one neutron and replace with a proton, the proton will leap out towards the shell surface, reducing sphericity and density and strength of the body.
"What has one sphere have to do with another?"
It's form, and therefore the relative position of the bonds.
Just because we use use different names for those bonds (strong force, gravity, sound, magnetism etc.) doesn't mean they are different, just that we perceive them differently based on scale and material. But the sphere form in relationship to it's sub-units doesn't change.
Simplest structure: tetrahedron 3D, triangle 2D
Simplest (least) surface area = most bonds/vol.: sphere/oid
The more bonds/vol the greater the gravity.
I think that's right, would need to verify with a physicist.
Hmm, sorry, a logic error I wrote stares back at me from the screen. Omit "If one has a double magic nucleus....".
Why don't blog comments (and yahoogroup/googlegroup posts) allow further editing? Or do they?
Thanks Raymond, I didn't know that lions dwelt in the Bili ape habitat.
David, would this be the article you were referring to regarding shapes? Proton shapes change...
http://www.scienceagogo.com/news/20030306212841data_trunc_sys.shtml
DD: Butted hand axe/adze remnants (Eritrea reef 125,000yrs) indicate possible dug-out construction.
DM: A quarter of a million years ago
DD: ?? "Do the math"? An eighth of a million years ago.
DM: is not "long before any kind of boat". I was talking about the several million years of human prehistory in South Africa, Chad, and so on.
DD: If one assumes that all those inland fossils are our ancestors (hypothetical), rather than relatives. South Africa is coastal (Langebaans...)
DD: but our ancestors were generally along coasts and near-shore isles.
DM: You state this as if it were a fact, but it is an inference from your hypothesis.
DD: Aside from volcanos, quakes, tornados, comet impacts, etc. the highest energy exchange locales on Earth are at the tidal shores where water, air and rock meet every day 24/7. Evidence of past shoredwelling typicaly is ground and recycled quickly there. This makes evidence hard to come by, for ancient narwhals and sirenians as much as ancient humans.
Photic (Sun) Sneeze Reflex (PSR): [From a sneezing website] "During a high school biology class, we tested the phenomenon by shining a spotlight into the eyes of a fairly large group of volunteers (one at a time). Almost everyone sneezed at least once when the bright light was shone into their eyes briefly, and the most susceptible people sneezed repeatedly until the light was no longer directed at their faces." [They would have stopped sneezing if they had closed their eyes]
PSR occurs in about 1/3 the European population (Left-handedness occurs in about 1/10 the European population), but the sensitivity level is highly variable, as would be expected since the PSR no longer has any functional benefit, and has become vestigial.
One would expect that a marine iguana population, if removed to a zoo and fed less salty foods progressively for multiple generations, living in a brackish and then freshwater habitat, would also eventually lose it's salt-sneezing tendencies genetically, with the salt glands and sneezing becoming reduced to mere vestiges. Arid-habitat and freshwater arboreal iguanas don't sneeze (too water costly in arid habitat, unnecessary in freshwater habitat), only marine iguanas do.
Both cetaceans and walruses produce high-speed exhalatory spouts using high pressure differentials which are the result of massively different gaseous ambient pressures at depth and at surface.
Did archosaurs, ichthyosaurs, etc. sneeze-exhale? Did they have simple sonar or "whale song"? Could they produce oral or intranarial clicks? Too many unknowns.
DM: 1. Why? 2. Which apes actually have a laryngeal air sac?
DD: 1. Emergency Life jacket (Mae West) filled with exhaled air during hyperventilating when immersed (face out of water). This was cause of tail loss, habitual semi-vertical float-wading, and indicated by shape of hyoid. 2. All (including Apiths and tail-less Miocene apes AFAIK) but vestigial in small gibbon (left shores) and human (dive-foraging/back-floating team).
DD: Darwin found no sun-frown and assumably no sun-sneeze when he tested a young chimp and orang from very dark to bright light conditions.
DM: One chimp and one orang-utan! What a compelling sample.
DD: Why would they sun-sneeze? Their ancestors did no diving. Salt-water crocs shed tears, freshwater crocs don't. Marine iguanas sneeze, freshwater iguanas don't.
(Formerly seashore) humans sun sneeze, inland apes don't.
DD: PSR: Uniquely human AFAIK [See other post on PSR]
likely similar to marine iguanas which look at the sun and sneeze to remove salt brine from nasal glands (they dive and eat salty seaweed).
DM: But surely you have noticed that we don't have any salt glands whatsoever, which makes sneezing entirely useless in getting rid of salt? While I am at it, what does the sun have to do with all that? Why don't the marine iguanas simply sneeze after every dive? Or do they?
DD: Our mucus is very saline, with a pH approx. equal to seawater. Sunlight triggered the sneeze (pressurised exhalation) as diver approached the well-lit surface.
Marine iguanas emerge and move to sunny spot, face the sun and sneeze, the white (reflective) salty mucus typically lands on the forehead, where it keeps the brain cool while basking in the hot sun.
Human ancestors instead had long wet head hair which kept the brain cool while basking in the hot sun after diving, and the sneezing was done during the dive cycle (like whales and walruses) rather than afterwards.
DD: The photic sneeze exhales old air from the body entirely at roughly the same speed as a dolphin ventilatory cycle, far faster than a normal aerobic exhale in a human.
DM: And? (If we do that too often, our blood becomes basic, and we run into serious trouble...)
DD: Too often = disease. Normally 1-4 sneezes, removed CO2, flushed fresh air instantly at surface, reduced over-acidity from CO2 build-up, prepared for next dive without dependence on hyperventilation (potentially dangerous).
DD: No apes live on tidal waters
DM: So what?
DD: If they were allowed to, they would eventually become more human-like (parallel convergence), losing their inland traits.
DD: apes developed their derivations (eg. longer fingers) as they moved from the coasts inland.
DM: No, we shortened ours when we stopped climbing every day.
DD: Evidence? I was thinking of gibbons, orangs (+Atelidae).
Our hands resemble newborn macaque hands, not under-branch swinging.
DM: BTW, do you consider 4 owl eggs, produced, shelled and laid once at a time, a "mass"?
DD: Yes, considering owls must carry the egg making materials in-flight in air and also nest in smallish tree hollows (I assume), the egg mass (quantity) is much less than a sea turtle mass.
DM: Oblong crocodile eggs are produced, shelled and laid all in one sitting.
DD: Crocs don't fly. (Well, I haven't read ALL of Darren's posts, maybe he's found one that does?) Crocs have a bizarre history, but I assume they've always had freshwater riverside nesting ancestors.
My point though, was that spheroid eggs are simplest and primitive, all other shell shapes are due to selections acting against spheroid eggs.
Click on link for Bigfoot Bunny pic and egg stacking & packing. Good holliday!
Chick Rex? Similarities of protein between chickens and T. rex
Thanks for the bunny photo! I'm stunned.
DD: Crocs don't fly.
You know... at least tetanurans in general produce, shell and lay one egg per oviduct at once, not many at once as crocodiles do. (In flying birds, only one ovary is functional, resulting in a single egg being laid at once.) Thus, it can't have anything to do with flight.
That may well be -- but it doesn't tell us anything about your other point, which was explaining to us that the original condition both for flying theropods as a whole and for Neornithes was a strongly pointed egg.
Unsurprising.
There's only room for a certain number of nucleons in every shell, just like there's only room for a certain number of electrons in every orbital. A nucleus in which all shells are full is spherical -- all others are, to varying degrees, off.
No, this is something completely different.
This has nothing to do with density or gravity! The total mass of the nucleus, and thus its gravity, doesn't change when its parts rearrange themselves -- obviously.
And no, gravity and the strong nuclear force are not even remotely the same.
Wrong. This has nothing to do with surface tension = the tendency of every water molecule to have the largest possible number of hydrogen bonds and thus to not be at the surface. The water in an egg has no surface tension because it has no surface that borders anything unpolar (like air)! It is about packing the largest volume into the smallest linear dimensions and/or having the least material to use for building the shell.
Just because we use use different names for those bonds (strong force, gravity, sound, magnetism etc.) doesn't mean they are different, just that we perceive them differently based on scale and material.
Well, on a deep level, they can be described together... except sound. How is sound a bond?
They don't. I suppose it would require too big program files to load into your browser and to store on the webspace.
You have missed the point. Even if none of the currently known fossils is a direct ancestor of us, we still can't escape the conclusion that they are all closely related to us and from inland environments. Parsimony says that our direct ancestors must therefore have lived in inland environments, too. Unless we find evidence to the contrary, we must accept this hypothesis.
How old is Langebaans? (Never heard of it.)
What is your point? That you can explain away the lack of evidence for the coastal human ancestors that your hypothesis requires? This makes it less scientific, not more. Besides, the sirenian fossil record is very good, from the Eocene all the way to now, and even though we still don't understand what they were, we have a lot of desmostylians that are interpreted as having lived on shores; again, I don't understand your point.
Look, this is great, this is interesting in its own right -- but obviously it can't tell us anything about humans. Why? Because (I repeat) we have neither salt glands nor any vestiges of ones. The only ways we excrete salt are sweat, tears, and urine (none of which we can make as salty as seawater -- which is why you can die of thirst in the sea in the first place). Whatever the reason is photic sneezing exists, it cannot possibly be salt. That's called the slaying of a beautiful hypothesis by an ugly fact.
You say it: as soon as they open their noses, the water pressure squeezes the air out of their lungs. Inhaling requires muscle force in a whale or walrus, exhaling doesn't.
Be patient, young padawan. The answer to the first question is indeed unknown -- except for archosaurs: the extant archosaurs, crocodiles and birds, don't sneeze AFAIK. The second, however, is easy to find: none of them, AFAIK, shows any adaptations to hearing in water, and while plesiosaurs have some for smelling in water, ichthyosaurs have those humongous eyes. If you see everything, you don't need to hear. Did you read about the recent discovery of that ancient predatory mysticete? No trace of adaptations to sonar, but huge eyes for a mammal.
I don't understand. Please explain.
BTW, good that you mention "semi-vertical float-wading". In the rare cases that gibbons walk, they are bipedal. They are already used to having the body vertical (hanging from tree branches), so they stay that way when they stand or walk. Maybe human bipedality is a mere retention and the knuckle-walking of chimps and gorillas is an innovation instead...
Apart from again making the wrong connection with salt, your logic is circular: you mentioned one chimp and one orang-utan as evidence that photic sneezing is unique to humans, and when I ask how that can be a statistically significant sample, you use your conclusion to "show" that no evidence is necessary. Try again.
DD: Our mucus is very saline, with a pH approx. equal to seawater.
The pH is not the salt concentration. Besides, consider the amount of mucus a human can sneeze at once. Almost nothing. It would have to be incredibly salty to reach the efficacy of the salt gland of a marine iguana, crocodile, sea turtle, or sea bird.
Human ancestors instead had long wet head hair which kept the brain cool while basking in the hot sun after diving
It goes without saying that this is not the only existing explanation for why we haven't lost the head hair. Keeping the brain cool while standing in a savanna is the current favorite. For long hair, try sexual selection.
Normally 1-4 sneezes, removed CO2, flushed fresh air instantly at surface, reduced over-acidity from CO2 build-up, prepared for next dive without dependence on hyperventilation (potentially dangerous).
Ah, an explanation for photic sneezing which still uses diving but doesn't require fictitious salt glands. Good! Honestly -- I'm not kidding. Now show me that photic sneezing is unique to humans among primates, and explain why small diving mammals don't sneeze, and you will have a point.
This may be testable, but I can't think of a way to test it. If you can, please tell me. (If nobody can, it's not science.)
DD: Evidence?
Parsimony applied to phylogeny.
Oops! Sorry. :-)
By David Marjanovi? (not verified) on 13 Apr 2007 #permalink
Please click the Blue DDeden for salinity of mucus (and also "Sneezing at the light" blog post) at this comparative anatomy blog.
The pH (acidity/basicity, not salinity) of mucus is the same as average seawater, the salinity of inter-cellular fluids is 9 parts per thousand (between the baltic sea and the Caspian sea), but I've not yet found of the salinity of mucus, although it is Hypertonic, so there is clearly salt concentration there. Since humans (and formerly gorillas and chimps) have alternative methods of removing salt, salt glands would be far less necessary than in seabirds which lack eccrine sweat glands AFAIK. The primary function of the photic sneeze was respiratory, not salt removal. It was part of the Aqua-photic Respiratory Cycle, used while dive-foraging for shellfish at tidal tropical shores.
DM: Parsimony applied to phylogeny.
DD: Umm, no. Do you think our ancestors were brachiating knuckle-walkers like chimps? David, brachiating and knuckle-walking are inland arboreal-terrestrial traits derived from former estuarboreal float-wading bipedal hominid ancestors, great when living with cats but of no use at the tidal seashores where our ancestors were. OTOH if you go to a sunny sandy beach you will see small infants knee-crawling on the sand, something that savanna chimps and arboreal apes don't do, being clingers. Our head hair, in addition to brain cooling, allows infants to cling while floating (pregnant women's hair strengthens), but not so good for terrestrial or arboreal clinging. The inland frizzy hair is "recently" derived from the primitive long head hair of coastal ancestors, selected in response to body lice which carry typhus, only occurred with the improvement in dugout boat construction associated with hand axes/adzes allowing early sapiens safe access to the interior.
DM: That you can explain away the lack of evidence for the coastal human ancestors that your hypothesis requires? This makes it less scientific, not more.
DD: Lack of evidence? Didn't I mention the Eritrean reef 1/8ma?
Please explain how that is not evidence of seashore dwelling human ancestors.
DM: I don't understand. Please explain.
DD: It's simple. Throat "Airbags" (like frog vocal sacs, walrus pharyngeal air sac) allowed semi-vertical float-wading in Hominoids when immersed, this produced functional bipedal gait like gibbons (but at that time there were no fast brachiators). Normal terrestrial quadrupedalism was lost due to habitual float-wading posture combined with tidal forest arboreal climbing. Knucklewalking and fistwalking independently derived when ancestors of chimps, gorillas, orangutans expanded inland and needed faster terrestrial locomotion.
DM: BTW, good that you mention "semi-vertical float-wading". In the rare cases that gibbons walk, they are bipedal. They are already used to having the body vertical (hanging from tree branches), so they stay that way when they stand or walk. Maybe human bipedality is a mere retention and the knuckle-walking of chimps and gorillas is an innovation instead..
DD: Yes. (Must rush off)
That the nasal irrigation is done with saline is not surprising. Two words for you: "physiological saline". The post doesn't mention at all how salty mucus is, and neither do the comments except your second one. (Incidentally, your first one arguably counts as spam.)
The post on photic sneezing is very interesting. You should read it. (You have commented it, but your comment hardly has a connection to the post; it arguably counts as spam.)
Since humans (and formerly gorillas and chimps) have alternative methods of removing salt, salt glands would be far less necessary than in seabirds which lack eccrine sweat glands AFAIK.
Then why can we die of thirst in the sea? Because we can't remove enough salt, that's why. Seawater contains 3 % salt, we can't get our urine to more than 2 %, and I bet our sweat can't even reach that. No matter how hypertonic mucus is, we'd need to produce gihugrongous amounts of it to remove enough salt for making drinking seawater possible. Give up. Look for another explanation for photic sneezing.
The primary function of the photic sneeze was respiratory, not salt removal.
Oh, you have already done that. Good (but see my last post). Then why do you still mention the salt at all?
Incidentally, can you explain the sweat? It's great for running in open country, but totally useless in the sea. Hm... you haven't tried to explain the human ability to run long distances at all so far.
the Aqua-photic Respiratory Cycle
If you keep making up unnecessary technical terms and throwing them around as if everyone already knew them, everyone will get the impression you're a crank. (Fortunately this one is easy to understand.)
Do you think our ancestors were brachiating knuckle-walkers like chimps?
Knuckle-walking, I'm not sure. (There was a debate about supposed vestigial adaptations to knuckle-walking in Australopithecus afarensis; I don't know how, or whether, it has ended.) Brachiating, yes, obviously. Why else are our arms and shoulder girdles so absurdly mobile? For swimming you don't need to be able to rotate your hands by (in sum) almost 360°. You don't need such ridiculously long arms in the first place; compare frogs.
David, brachiating and knuckle-walking are inland arboreal-terrestrial traits derived from former estuarboreal float-wading bipedal hominid ancestors
Repeating a claim is not the same as providing evidence for it.
OTOH if you go to a sunny sandy beach you will see small infants knee-crawling on the sand, something that savanna chimps and arboreal apes don't do, being clingers.
We aren't arboreal anymore, so our legs have become longer than our arms...
Our head hair, in addition to brain cooling, allows infants to cling while floating (pregnant women's hair strengthens), but not so good for terrestrial or arboreal clinging.
Why not for terrestrial one? Remember the usual explanation for why we have so short hair on most of the body but long hair on the head: for not overheating in the savanna.
selected in response to body lice which carry typhus
Then why does any terrestrial mammal have fur? Come on.
Lack of evidence? Didn't I mention the Eritrean reef 1/8ma?
What, and that you call "human ancestors"? That fits even the narrowest definitions of "human", even those under which the Neandertalers are not called "humans". 125 ka is younger than Mitochondrial Eve and Y-Chromosome Adam even. The first emigration of Homo sapiens sapiens from Africa is estimated at around 100 ka ago... hey, why didn't "coast-dwelling human ancestors" emigrate much earlier?
It's simple. Throat "Airbags" (like frog vocal sacs, walrus pharyngeal air sac) allowed semi-vertical float-wading in Hominoids when immersed
Aha. I have a couple questions: Why don't walruses and frogs float "semi-vertically"? Why do we do it so effortlessly with no other large air container than the lungs?
You have fallen in love with your hypothesis. You just want to believe it.
(but at that time there were no fast brachiators)
combined with tidal forest arboreal climbing.
Now let's see if climbing alone can have the same effect. ... Yes, it can. So why bother adding wading?
The adaptation to keep eggs from rolling out of a nest is not just an elongated egg, but an egg with one end larger than the other so that the egg rolls in a circle.
By Monado (not verified) on 15 May 2007 #permalink
Have A look at these Pterasaur hatchlings from California
http://www.pterodactylfossilsforsale.com/
By Kenneth Wegener (not verified) on 15 Apr 2009 #permalink
I regret to inform you that not one of the things on your website is a fossil. You should really learn some taphonomy (the science of embedding, fossilization, and everything else that happens to living beings after death). Also, the word "rhamphamorph" doesn't exist, "pterosaur" has an O, and your site is difficult to read because you begin almost every word with a capital letter.
By David MarjanoviÄ (not verified) on 16 Apr 2009 #permalink
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