Big brains seem to be pretty rare in the evolution of animals on this planet. One of the reasons for this is cost. Keeping our brain running is expensive. Just consider these facts.

750-1000ml of blood flow through the brain every minute. (3 soft drink cans worth)
In that minute the brain will consume 46cm3 (1/5 cups) of oxygen from that blood.
Your brain is about 2% of your total body weight but uses 20% of your body's energy.
The energy used by the brain is enough to light a 25 watt bulb.

In evolutionary terms this would make a big brain pretty rare. Think of any struggle between predator and prey. Say a lion and a gazelle for example. There's camouflage in their colouring so they are harder to see in long grass and there's speed and agility. The gazelle's ability to jump high. Now in this struggle the cost of either lion or gazelle to evolve a big brain is too big compared to what they'll lose in speed or agility before that brain would develop enough to make a real difference. This is true of most predator/prey relationships.

the other problem of developing a big brain is what do you use it for. You need a good way of manipulating the world for a brain to make use of it's abilities. Look at your hands, look at your thumbs. Brilliant for manipulating anything you come across. Perfect for grasping a stone or a stick to throw at or hit any approaching predator. Something to make up for what you lose running that expensive lump of grey matter.

Lots of the larger brained animals also tend to be social. Managing complex social relationships in a pack, group or family tends to increase the selective pressure on a larger brain.

So it has to be a situation in which there's a good selective pressure for a brain to grow to a large size in a body that has a good starting shape to take advantage of it.
Dolphins are pretty smart (and self aware) and so are parrots. They don't have a good body structure to really take advantage of it. A parrot can use it's beak and legs to manipulate simple odjects in a basic way, but it's nowhere near what a primate has.
Now for a creature that has a pretty big brain and decent limbs for manipulating objects other than primates look at the octopus. That is one smart animal. If humans were to become extint, that's the animal other than chimps and gorillas that might be a candidate for becoming super smart given the right selective pressures

There are other costs to a big brain. One is probably Schizophrenia (see link in the source section). It's also likely that our brain is as big as its going to get. Any further increase in size may well be disadvantagious due to the problems our brain has been left with growing to this size in the first place.

Brain size is only part of the story. Several bird species (African grey parrot, New Caledonian Crow, New Zealand kea) are all amazingly intelligent, and they have brains that can fit in the top half of your thumb. Obviously, they cannot afford heavy brains, because that would handicap flight. But they are pretty damn smart all the same.

"Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill"nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke

Racoons - Very smart small mammals, with hands (but no opposable thumb)

Elephants - Considered to be the dominant species before humanity arose to assume that honor. Their truck gives them a means of manipulating their environment.

I think it's safe to say that, if the monkeys hadn't claimed it first, there are several species that were in a position to evolve higher intelligence. However, high intelligence massively increases a species' rate of progress. Since we arrived first, now we've had time to rocket several stages of advancement ahead of them. I think it's unlikely the others will even live long enough to catch up.

Some clocks are only right twice a day, but they are still right when they are right.

"Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill"nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke

There are a lot of intelligent beings on earth. It's also important how your body is, e.g. limbs; humans have good limbs to do complex stuff with their intelligence, also apes and octupuses. Most animals didn't use their brains as much as humans did, so we developed our brains far more, but it takes extremely long for the evolution of a brain to finally come to a stage where you can do amazing things with it (e.g. maths, physics, philosophy). This is what makes us, humans, so different from animals, we're innovative and we do complex things no other being on earth does. All life on earth started as a cell and evolved into more complex life as we see today, it's just a tremendous achievement of evolution that it also created super intelligent beings that can actually use their brain to their full potential: humans, a specie that is able to go to the deepest depths of the ocean and to space, as it is today to even other nearby worlds.

As far as I can make out, the only thing that sets humanity apart as unique, is that we are the only species that makes use of advanced (knapped stones or better) technology.

There are other species able to solve problems, or perform pretty much any mental feat humans can. There are animals with larger brains. Animals with what appears to be language. As adelady pointed out, animals able to count. And so on.

It is our physical traits that allowed us the maximum allowance of brain mass to develop grammatical language, writing it down to past on to further generations to build upon that knowledge. This was the basic foundation for technology to develop and build from there. The ability to reproduce in such great numbers allowed certain individuals to be born with the ability to invent new things which benefited all of us. Intelligence exists on all levels of life and if we only chose to define it as compared to how we measure ours then of course humans would think they are more intelligent then other creatures.

if we only chose to define it as compared to how we measure ours then of course humans would think they are more intelligent then other creatures.

Let's face it. We've only applied our own intelligence to trying to understand other animals' intelligence (and forms of language) fairly recently. Even then we've made simple, obvious mistakes in that. See this item on reptiles. Temperature is a truly Duh! parameter when looking at any activity with reptiles, but noone thought of it in their experimental design up until now.

"Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill"nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke

It is our physical traits that allowed us the maximum allowance of brain mass to develop grammatical language, writing it down to past on to further generations to build upon that knowledge. This was the basic foundation for technology to develop and build from there. The ability to reproduce in such great numbers allowed certain individuals to be born with the ability to invent new thingswhich benefited all of us. Intelligence exists on all levels of life and if we only chose to define it as compared to how we measure ours then of course humans would think they are more intelligent then other creatures.

Very well observed. If only everyone was like you to put their ego aside and understand that true intelligence is a special type of energy that only certain individuals are born with.

Almost all humans are intelligent enough to use language, and to use tools in a sophisticated way.
I do not think your suggestion, that only a few individuals can be called intelligent, stands up. Compared to almost any other species, even our less intelligent individuals are geniuses.

Humans can be better at using their mental abilities to justify poor decision making than they are at using their intelligence to make good ones. Even knowing from experience combined with the use of logic that our choices are bad ones won't necessarily be enough to kick our intelligence into gear and cause us to change our behaviour, so it's clearly a deeply flawed form of 'superior' intelligence.

Humans can be better at using their mental abilities to justify poor decision making than they are at using their intelligence to make good ones. Even knowing from experience combined with the use of logic that our choices are bad ones won't necessarily be enough to kick our intelligence into gear and cause us to change our behaviour, so it's clearly a deeply flawed form of 'superior' intelligence.

Humans can be better at using their mental abilities to justify poor decision making than they are at using their intelligence to make good ones. Even knowing from experience combined with the use of logic that our choices are bad ones won't necessarily be enough to kick our intelligence into gear and cause us to change our behaviour, so it's clearly a deeply flawed form of 'superior' intelligence.

Our intelligence is devoted mostly to rationalising rather than to rational thought. Our brains are hardwired to recognise patterns - so much so that we 'see' them even when they don't exist. Astrology is a good example of this. Lots of calculation, logical reasoning and other apparently rational processes all applied to an irrational premise based on selective pattern seeking behaviour.

Another one is rationally assessing the 'stupidity' and 'irrationality' of others. Driving those who are in fact both intelligent and rational to seek "least worst" outcomes by taking others' wrongheaded decision making into account. Survival Of The Stupidest
(Perhaps this is how politicians come to be so poorly regarded. They have to take into account the views of people who believe that daylight saving fades the curtains - along with other follies and furphies. We can avoid such people if we want to, politicians are stuck with the citizens they've got.)

If you factor in all the cognitive science and psychological insights to the decision making mix, you'd almost be ready to think we're not so clever after all.

"Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill"nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke

Without denying we have intelligence that other animals don't it's clear that it has real limitations. Even with relatively simple tasks a lot of people can have real problems. And then there are those individuals who clearly demonstrate remarkable reasoning abilities yet who can still be short-sighted, gullible and resistant to new knowledge or contrary reasoning.

Interesting links Adelady. I think it does have a lot to do with the back and forth with other people, whether it's about self interest or demonstrating dominance or avoiding conflict or indicating that you are part of a group. It's clear that there's a lot more going on than abstract reasoning.

Where our institutions, such as academic/scientific ones, fit into that by redirecting and moderating those non-rational aspects of human reasoning is interesting too. Competitive urges amongst academics vying for recognition is moderated both by physical distance and by conventions and rules. I suspect when it was mostly done face to face before ones' peers it could've gotten quite heated. And occasionally physical. And sometimes taking a generational change for new ideas to get recognised.

And sometimes taking a generational change for new ideas to get recognised.

Generational change?

Who was it said that new scientific discoveries don't win the "debate", it's just that the old scientists die out?

"Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill"nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke

Almost all humans are intelligent enough to use language, and to use tools in a sophisticated way.
I do not think your suggestion, that only a few individuals can be called intelligent, stands up. Compared to almost any other species, even our less intelligent individuals are geniuses.

Nikola Tesla.

Genius is creativity beyond what everyone else sees. You can read every book on this planet, store it in your brain and still be where you started if you can't improve on what you learnt or see the mistakes in someone elses work.

Tesla, Einstein, Newton, Bohr, Russell, Whitehead and every Nobel Prize winner you can think of were pretty clever. But every single one of them sees further than others only by "standing on the shoulders of giants".

We can be pretty certain that there were plenty of people many centuries ago who had the raw 'genius' or intelligence to make great discoveries - but not in maths or physics. People who'd not yet learned to use zero were in a very poor position to invent calculus or any other sophisticated mathematical or scientific process.

There are always supremely intelligent people. But their skills can come to the fore only in societies that accumulate and transmit the acquired body of knowledge to each successive generation.

"Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill"nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke

if we only chose to define it as compared to how we measure ours then of course humans would think they are more intelligent then other creatures.

Let's face it. We've only applied our own intelligence to trying to understand other animals' intelligence (and forms of language) fairly recently. Even then we've made simple, obvious mistakes in that. See this item on reptiles. Temperature is a truly Duh! parameter when looking at any activity with reptiles, but noone thought of it in their experimental design up until now.

Tesla, Einstein, Newton, Bohr, Russell, Whitehead and every Nobel Prize winner you can think of were pretty clever. But every single one of them sees further than others only by "standing on the shoulders of giants".

We can be pretty certain that there were plenty of people many centuries ago who had the raw 'genius' or intelligence to make great discoveries - but not in maths or physics. People who'd not yet learned to use zero were in a very poor position to invent calculus or any other sophisticated mathematical or scientific process.

There are always supremely intelligent people. But their skills can come to the fore only in societies that accumulate and transmit the acquired body of knowledge to each successive generation.

Mathematics will never see the illusion in the universe. 1+1 will always equal 2 and you can make equations as complex as you want; they will never relate to reality.

Mathematics is just a measurement of what you can see. Can you measure what you are not able to see?

They can see further than others because they've stepped away from the limitations of mathematics.

"Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill"nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke

Well, there is also "pure mathematics", as beloved by many geniuses, which is only used to build more mathematics. In that sense it is unlimited. A bit like art.

You basically proved my point. It makes them geniuses because they can write new lines that don't correlate what so ever with reality? Sounds like insanity.

Nothing man-made is complex. Its all simple+simple+simple+simple which looks complex. Whats complex is looking at a person of the opposite sex and exchaging energies that cannot be seen. You won't know until you've experienced it. Physics will never be able to explain the illusion of the universe.

"intelligence" is a human construct, a label. Humans are more intelligent than other species as far as we know but I dont think the all or nothing black/white "intelligent or not" ("the only intelligent") helps understanding.

Put the infant Nikolas Tesla in a Bonobo Chimp family (that adopts him) that lives in the jungle wilderness without any human contact and by age 20 he might be less functional in a human civilization than an grade 10 student of average "intelligence". He sure as hell will not speak and might have more trouble learning about a lot of stuff from literacy to mathematics than people expect. Put a bunch of humans among chimps to form chimp-ish tribes and it might take many generations before they develop neolithic tools and control fire (the way a adult caveman or a teenage boyscout could). Our current civilization is based on continual accumulation and transmission of information (and tools/methods). We are more intelligent than other animals and maybe a bit more so than cavemen, but not a 100 times more so (yes we are no they aint) because we have intercontinental airline flights and gps satellites which is probably accessible to cavemanish intelligence give enough time and social evolution.

"There's camouflage in their colouring so they are harder to see"Eyes just transmit signals, parts of the brain see, that is it creates a representation of reality and interprets the signals based on reality templates, and understands what goes on around and realizes that a predator or prey still exists when its no longer seen while behind an visual obstacle. Tiny animals ability to see with a tiny brain is amazing, and what bees can do with a tiny brain is also impressive, not too smart but wired to do just the thing that was most adequate given the environment in which they have lived in. A person with a mental deficiency has probably the same brain mass as someone else but problems in the wiring/signal fluidity/or something. Maybe brain "size" is a bit overvalued.

We tend to view the evolution of intelligence as some simple progression. Almost as if it's an inevitability that any species showing moderate intelligence will start questing for fire some day. It seems to make sense, in a human-centric kind of way. Our level of intelligence has certainly done us wonders, so why shouldn't it be selected for in other animals? But one of the big problems with intelligence is that it's very costly. Up to 20% of the energy you take in is used to power your brain. That's energy that could be spent on better legs for running, better jaw muscles for biting, better arms for climbing. Now add on top of that the apparent fact that high intelligence is really hard to get to. We see convergent evolution all the time with general structures like wings, fins, ect. But as far as intelligence goes, the most we see is basic problem solving, social intelligence, and planning. The kind of stuff that's useful to opportunists like wolves, crows, primates, ect. Granted, there's a lot more intelligence there than we previously thought, and we've found ourselves humbled many times, but we still haven't found our intellectual equals just yet. The reason, presumably, is because it isn't so simple to evolve our kind of intelligence and there's actually an energy limitation that works against it. There is no real clear, logical progression from "intelligent" to "contemplating contemplation." Our intelligence was apparently a byproduct of a series of short-sighted evolutionary adaptations with no long-term driving force behind them.

For example, our ancestors may have needed free hands in order to make precise tools, but they only had free hands in the first place because walking upright was more efficient than walking on their knuckles. The advantage had more to do with being migratory than it did with being intelligent. And even then, it's not like walking upright leads to intelligence either, since we went for so long without it happening. There's obviously something else involved in the formation of our bigger, more complex, brains and the fact that it isn't immediately apparent shows that it's not the kind of thing that was inevitable.

Then there's the whole developmental aspect. Human brains are born underdeveloped compared to other primates because of our narrow birth canal. As a result, our infants start interacting with the world well before their basic motor, memory, and cognitive functions are fully developed. This resulted in an uncanny ability to pick things up at a level that cannot be repeated later in life. So even with whatever genes it is that makes our brains grow so big, how sophisticated would our languages be if that development happened inside a womb? And how many of our complex ideas are dependent upon our ability to articulate them?

My point is that these events -- developing hands, walking upright, growing bigger brains... -- are evolutionary side-tracks, not logical progressions, that compound to make the covergent evolution of similarly intelligent animals all the more unlikely. Why are we the only ones? Because we're lucky (or unlucky, depending on your point of view.)

[blockquote]...it might take many generations before they develop neolithic tools and control fire[/blockquote]

I'd agree with that; even inventiveness arises from experience of tools and of variations producing different results. A friend needed a thin phillips head screw driver but didn't think to file a shaped point from a readily available piece of heavy wire of suitable diameter. I don't think I was more intelligent for thinking of that - just more exposed to the possibilities of pieces of metal being shaped into suitable tools by filing.

...it might take many generations before they develop neolithic tools and control fire

I'd agree with that; even inventiveness arises from experience of tools and of variations producing different results. A friend needed a thin phillips head screw driver but didn't think to file a shaped point from a readily available piece of heavy wire of suitable diameter. I don't think I was more intelligent for thinking of that - just more exposed to the possibilities of pieces of metal being shaped into suitable tools by filing.

Humans have been around for a long time but it wasn't until education was provided to the whole population where everyone learned to read and write that the capacity to write all of our knowledge into books was the key to our success. Every generation contributed to adding and building more information and this allowed specialization in all those areas of interest that allowed all of the wonderful inventions and discoveries that is valuable to mankind.

This is the biggest contributing factor that separates us from other species in that we can learn knowledge from all the generations before us that contributed to the pool of information. In other species, information is limited in that there is no mechanism that allows every bit of knowledge a place that it can be stored for future generations. Instincts are limited to how much information can be passed on to future generations and is designed for improving the odds of survival whereas our system allows information to be built for future inventions and discoveries.

I think people give animals less credit than they deserve. If they cannot communicate with language like we do, or have the tools needed (thumbs) to manipulate the environment - that doesent mean they dont feel, or arent smart. They just dont have the tools to develop it like we do.

If a person was trapped in an animal body - how would you know? You couldnt communicate or "give yourself away". You would be standing there sniffing, licking and jumping around like "HEY BOB ITS ME FOR CHRIST SAKE!" only to receive a pat on your head.

A lie is a lie even if everyone believes it. The truth is the truth even if nobody believes it. - David Stevens

If a person was trapped in an animal body - how would you know? You couldnt communicate or "give yourself away". You would be standing there sniffing, licking and jumping around like "HEY BOB ITS ME FOR CHRIST SAKE!" only to receive a pat on your head.

You couldn't figure out how to claw out a few words on the lawn? "Help, it's me!"

Body language exhibited is a global language that we all instinctively understand between our species and all other species. Our ability for speech that allowed us to build our library of language is unigue to humans but it does not make us any more intelligence then other creatures that do not possess the ability for speech. Our unigue body appearance allowed us the ability to build our environment tailored to our needs and this is the major difference between us and other species.

Most everyday chitchat is meaningless and its only benefit is that it allows social behavior to be cooperative with other members of our species.

In terms of brain structure, the key thing for intelligence apears to be number of connections. So far, it appears that humans have more brain connections than any other beast. This makes us the most intelligent.

We are also the only animal known to have a detailed and versatile language, and we are definitely the only animal known to have intricate technology.

Face it. Trying to say other animals are just as smart is a bit silly.

skeptic,
For a moment imagine just you alone were in the jungles all by yourself with no weapons along with all of the other species in the jungle and lets see how long you were be able to survive. You ability to speak or to learn about technology would not do you a bit of good in a different environment. It is the human ego that believes they are the most intelligent on the planet but it is an illusion to believe that it is at the individual level.

In terms of brain structure, the key thing for intelligence apears to be number of connections. So far, it appears that humans have more brain connections than any other beast. This makes us the most intelligent.

We are also the only animal known to have a detailed and versatile language, and we are definitely the only animal known to have intricate technology.

Face it. Trying to say other animals are just as smart is a bit silly.

If we have more brain connections then why did it take so long to develop our technology since this is rather recent compared to how long our species has existed?

Our ability for language and the recent development of technology that allows all information to be shared globally is no doubt escalating our success in so many advances in science. But it could also be our downfall with the global destruction and creating so many extinctions in other species that our supposely "intelligence" will be viewed by natural selection as a undesirable trait. There is a reason why every species has its own form of communication that acts as a barrier to other species being able to translate it.

skeptic,
For a moment imagine just you alone were in the jungles all by yourself with no weapons along with all of the other species in the jungle and lets see how long you were be able to survive. You ability to speak or to learn about technology would not do you a bit of good in a different environment. It is the human ego that believes they are the most intelligent on the planet but it is an illusion to believe that it is at the individual level.

Not a smart example.

We have no claws, talons, long teeth, or even strong arms for defense or hunting. The reason we have none of those things is because humanity evolved to use technology. Technology is our claws, talons, teeth and strong arms. To leave a human alone in the jungle with no technology is like cutting off a jaguars paws and claws, and removing its teeth, and watching it starve to death, because it cannot hunt.

We survive and thrive from technology and from social cooperation. Both driven by our intelligence. Remove society and technology, and we will die. Of course. But that is not evidence of lack of intelligence. Just evidence that removing the special adaptations for survival cause lack of survival.

"why did it take so long to develop our technology since this is rather recent compared to how long our species has existed?"

It didn't.
If we look at our ancestry, we see a close relationship between level of technology and evolutionary development. Our ancestor Australopithecus, which lived 3.5 million years ago, had a small brain (similar in size to a modern chimp), and there is little sign of much technology. Homo habilis, on the other hand, from 2 million years ago, had a much larger brain and was knapping stone tools, and using fire. Homo erectus, from 1 million years ago, had much more sophisticated stone tools and a larger brain still. Homo sapiens, with the largest brain, has the greatest technology development. A very direct relationship between brain size and sophistication in technology.

That's sort of like asking why the cheetah is the only fast animal on land. First of all, it would better worded to say "why are cheetahs the fastest land animal?" since speed or intelligence or other qualifier lies along a continuum.

On that note, I would answer both questions "why are humans the most intelligent beings on earth?" and "why are cheetahs the fastest land animal?" the same way:

The kindergarten answer is because, logically, some species has to be the best at a given skill.

The better answer is that the species evolved a characteristic that contributed to its survival, thus perpetuating that characteristic. It's our evolutionary niche.

Humans have been around for a long time but it wasn't until education was provided to the whole population where everyone learned to read and write that the capacity to write all of our knowledge into books was the key to our success.

this made me think of the huge differences between technology in europe and its surroundings and isolated tribes who even until recently probably lived more or less like they and others(europeans/etc) lived thousands of years ago so education(locally) and travel/contact/exchange-of-knowledge(globally) appear important.

Going back on the OP's question, the way we ambiguously define intelligence could apply to several species, even whole genera, in my opinion. Dolphins and pigs, for example, are relatively intelligent animals.

A better phrasing of the question would be "Why are humans the only sapient beings on Earth?"

If I understood the question right, you basically asked why intelligence would be pressured in an evolutionary scenario when physical advantages seem more probable. Well, natural selection isn't just about physical ability. Our ancestral hominid-like primates might have just gained a larger brain volume through chance occurrences. And whatever intelligence they helped them survive and reproduce.

Brain volume has a positive correlation to intelligence (within the human species), so it's possible the more intelligent human-like beings survived better while the less intelligent eventually died off, in a broad sense. We might not be able to outrun a cheetah, outweigh an elephant, fly, swim a mile, or anything like that... but look where technology has gotten us. Like I just stated in another thread, "we are the most intelligent, environmentally influential, and powerful form of life known to us".

There might also be a feedback loop effect between intelligence and the duration of absolute dependance of babies. It probably helped that we could carry infants in our arms if at some period there was occasional nomadic journeys.

... human infants are born with only 25% of their brains fully developed, compared to chimpanzees, whose offspring are born with 45-50% brain development....
Since human infants are born so early, they spend more than a year in a nearly incapacitated state. Therefore, human infants depend on their parents much more and for much longer than other primates. .

"Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill"nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke

Speaking of newborn brains, another (unique, I think?) peculiarity of humans is the normalcy of brain trauma during birth. We have rubbery skulls in which our less flexible brains literally squeeze and slosh forward to escape the birth canal. So cerebral hemorrhage and massive loss of neurons is normal for our oversized brains - why?

I wonder if there could be a kind of genetic disagreement behind this, for while paternal genes help determine baby's brain diameter, only maternal genes determine gestation time, birth canal size/configuration, and duration of labour.

We have rubbery skulls in which our less flexible brains literally squeeze and slosh forward to escape the birth canal.

It's a trade-off.

Maximum brain development before birth means that the skull needs some flexibility. There are also hormone changes in the mother allowing normally rigid joints in the pelvis, back and hips to flex to accommodate both the large size of the baby and the expanded, highly stressed birth canal.

Both processes are variable. Without modern medical intervention, death and injury to either mother or baby or both occur reasonably often. It's one of the prices we pay for being human. It's one of the reasons to rejoice in the advances of medical knowledge that can prevent many of these problems in modern societies.

I don't quite get this. A woman's skeletal structure and musculature can be influenced as much by genes on her father's side as on her mother's. "Looking like" grandma or auntie doesn't just refer to the maternal line. And if there's a 'mismatch' between her pelvic size and a baby's skull configuration there's no good reason to attribute that automatically to the father's genes. It could just as easily be a genetic feature of her own family.

"Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill"nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke

I don't quite get this. A woman's skeletal structure and musculature can be influenced as much by genes on her father's side as on her mother's...

I'll expand the question:

So we've got a mother and a father. They're going to have a baby! Now, we're interested in what genes are passed to baby, particularly genes affecting (1) gestation and birth conditions, and, (2) brain size. We're wondering how (1) and (2) relate as they evolve.

(1) is already embodied in the mother. Her genes affecting gestation time, birth canal size/configuration, and duration of labour must apply to baby whether or not baby actually inherits them. The father's genes have absolutely no role in this. He has probably contributed some genes which had applied to his birth, but they can't apply to this impending birth.

(2) is largely determined at conception, by both mother and father. Mother's genes will propagate better if she has a relatively easy labour, thereby increasing her odds of having additional babies. Father's genes could propagate through additional babies even if delivering his oversized babies maims each mother.

I've outlined what is happening superficially and stopped, because I feel there is a dynamic in this I fail to see.

It is the pelvic structure that determines whether a woman will have an easier time delivery a baby and those genes can come from both the paternal and maternal side. If she is blessed with a wider pelvic structure, the baby can easily pass through the birth canal. The size of the baby is influenced by both sides.

No, her father's or mother's genes did affect her pelvic structure. What does brain size have to do with it? A baby's skull is not fully developed so it can pass through the birth canal with less difficulty. A brain no matter how large it is could be pass through the canal, it is the size of the skull that perhaps makes the difference.

I don't quite get this. A woman's skeletal structure and musculature can be influenced as much by genes on her father's side as on her mother's...

I'll expand the question:

So we've got a mother and a father. They're going to have a baby! Now, we're interested in what genes are passed to baby, particularly genes affecting (1) gestation and birth conditions, and, (2) brain size. We're wondering how (1) and (2) relate as they evolve.

(1) is already embodied in the mother. Her genes affecting gestation time, birth canal size/configuration, and duration of labour must apply to baby whether or not baby actually inherits them. The father's genes have absolutely no role in this. He has probably contributed some genes which had applied to his birth, but they can't apply to this impending birth.

(2) is largely determined at conception, by both mother and father. Mother's genes will propagate better if she has a relatively easy labour, thereby increasing her odds of having additional babies. Father's genes could propagate through additional babies even if delivering his oversized babies maims each mother.

I've outlined what is happening superficially and stopped, because I feel there is a dynamic in this I fail to see.

Prior to modern medicine, women dying in child labor was not unusual. A couple that has multiple children, the birth is different for each child.

There's also no doubt there there was selective pressure against extremely high birth weight and large heads because women died in child birth. Of course, from the low end there was selective pressure to increase birth weight (for viability) and head/brain size (less certain). Such presures are known as stabilization.

Availability of C-sections has removed the selective pressure against large size, so it would be no surprise, in the generations that follow, if we see directional movement of average birth size as well as larger heads.

I can imagine humans as a species a few centuries from now, where natural child birth isn't even possible anymore, but we've continued to get smarter with time due to genetics.

I'm gonna abandon my question, because I don't even know what I'm asking.

Originally Posted by Barbi

A brain no matter how large it is could be pass through the canal, it is the size of the skull that perhaps makes the difference.

That's not how it appears to me. The head seems to begin emerging while the brain is "far" behind. The head is acting like a firm brain within a more flexible container. At this point, delivery often stalls. The great moment appears to be not so much the whole head popping out, but the brain sliding forward within the head, which has already partially emerged.

In all three classes, and for a few adaptations, evolution is heading in a different direction. For example, embryos release chemicals to stimulate the placenta to pass on excessive amounts of nutrients. The mother has chemicals that oppose the embryo's chemicals, since that would weaken her.

There is advantage to the father in having the baby emerge really well developed, but that adds risk to the mother. So the different parties are subject to different evolutionary trends.

However, despite this and overall, evolution works more towards cooperation between the three parties to ensure successful reproduction.

In all three classes, and for a few adaptations, evolution is heading in a different direction. For example, embryos release chemicals to stimulate the placenta to pass on excessive amounts of nutrients. The mother has chemicals that oppose the embryo's chemicals, since that would weaken her.

There is advantage to the father in having the baby emerge really well developed, but that adds risk to the mother. So the different parties are subject to different evolutionary trends.

However, despite this and overall, evolution works more towards cooperation between the three parties to ensure successful reproduction.

The mother has chemicals that oppose the embryo's chemicals so the embryo doesn't end up taking all of the mother's nutrients since it would lead to starvation of the mother. Her chemicals act as a start and stop switch so nutrients are both supplied to mother and embryo. It is not heading in a different direction but a more cooperative one between mother and embryo.

How do (1) and (2) relate as they evolve? Can our large brains be justified in purely genetic terms? As an escalating conflict (or cooperation if you wish) of interests surrounding gestation and delivery?

Advantage to paternal genes the baby inherits, you mean. Since we're focusing on the problem of birth canal vs. brain size, we can almost regard these babies as adopted-out at birth.

I dunno about well-developed. Would you call a large brain well-developed when it suffers so much birth trauma the child's retarded? But since some degree of brain damage is normal and unremarkable, perhaps we're optimized for this. I mean the prenatal brain could have some redundancy or surplus, so it develops "perfectly" after the inevitable crush. I find it odd that C-section children, all else being equal, have the same IQs as those born vaginally.

The chemicals the baby creates to increase nutritive flow, and the chemicals the mother creates to stop that, create a balance. But the balance could be achieved if neither interfered chemically in the first place. The reason the two sets of chemicals exist, is a conflict between mother and offspring.

The advantage of a better developed baby is higher survival. But it comes at a price to the mother. The mother might die with her first baby, and never get the chance to reproduce again. So this creates a conflict. Father is benefited by more developed baby, while mother is harmed. Evolution can strike a balance, but not necessarily the best balance. Evolution is, after all, a pretty clumsy mechanism.

Tesla, Einstein, Newton, Bohr, Russell, Whitehead and every Nobel Prize winner you can think of were pretty clever. But every single one of them sees further than others only by "standing on the shoulders of giants".

We can be pretty certain that there were plenty of people many centuries ago who had the raw 'genius' or intelligence to make great discoveries - but not in maths or physics. People who'd not yet learned to use zero were in a very poor position to invent calculus or any other sophisticated mathematical or scientific process.

There are always supremely intelligent people. But their skills can come to the fore only in societies that accumulate and transmit the acquired body of knowledge to each successive generation.

This is why humans dominate. We have the best combination of tool use and community support. Wolves form into decent communities too, but alas no tool use. Racoons are good with tools, but not so much at forming communities.

Originally Posted by Barbi

Humans have been around for a long time but it wasn't until education was provided to the whole population where everyone learned to read and write that the capacity to write all of our knowledge into books was the key to our success. Every generation contributed to adding and building more information and this allowed specialization in all those areas of interest that allowed all of the wonderful inventions and discoveries that is valuable to mankind.

This is the biggest contributing factor that separates us from other species in that we can learn knowledge from all the generations before us that contributed to the pool of information. In other species, information is limited in that there is no mechanism that allows every bit of knowledge a place that it can be stored for future generations. Instincts are limited to how much information can be passed on to future generations and is designed for improving the odds of survival whereas our system allows information to be built for future inventions and discoveries.

It's almost like we evolve faster, because our knowledge evolves faster.

The first time someone discovered and proved that the Sun was the center of the solar system, and a generation came to believe it, the old idea immediately suffered total annihilation. The new idea "survived" at nearly 100% rate. Evolution's version of the same accomplishment would require some marginal percentage difference in survival rates to persist over maybe 2000 generations. It's no wonder we seem so far ahead of the other animals right now.

Some clocks are only right twice a day, but they are still right when they are right.

There is no doubt that humans have evolved faster because of our knowledge. The invention of electricity that allowed us to live in an ideal temperature in our homes and work environment was a huge contributor in that humans did not have to spend so much time trying to be comfortable with the gradients of temperature that other species must deal with in nature. With that not a factor we humans now could spend a great deal of time inventing and creating new ideas that allowed our success.

The chemicals the baby creates to increase nutritive flow, and the chemicals the mother creates to stop that, create a balance. But the balance could be achieved if neither interfered chemically in the first place. The reason the two sets of chemicals exist, is a conflict between mother and offspring.

The advantage of a better developed baby is higher survival. But it comes at a price to the mother. The mother might die with her first baby, and never get the chance to reproduce again. So this creates a conflict. Father is benefited by more developed baby, while mother is harmed. Evolution can strike a balance, but not necessarily the best balance. Evolution is, after all, a pretty clumsy mechanism.

Considering how life is believed to have started, I would never label it a clumsy mechanism. This view might stem from the fact that science doesn't know all of the intricate details in their understanding of it so far so it appears that it is clumsy right now.

Generate lots of offspring and award the prize of further reproduction to the ones that have a current minor advatnage and a bit of luck. Repeat ad infinitum. Tell me Barbi, what is not clumsy about that?

Generate lots of offspring and award the prize of further reproduction to the ones that have a current minor advatnage and a bit of luck. Repeat ad infinitum. Tell me Barbi, what is not clumsy about that?

In nature, how many of those offspring actually live to old age without reproducing? Probably none since predation is how those species that feed on them are needed so they can produce future offspring too. It is not clumsy when you consider it from the predator/prey mechanism which is how the food chain works.

Of course it is clumsy. The clue is in the element of chance that is present. If you design an aircraft you don't work on the basis that only some of them will make it to their destination with their passengers alive and well. That would be incompetent, clumsy design.

You are only seeing it from one side of the coin. Say you had to design an mammal but the rules of the game is a certain percentage of them must die for predation purposes. You wouldn't want them all perfect in design since this makes it difficult to give your percentage of the ones that must be killed for predation purposes. In order to keep the game going for generations, you would want a selected few to reproduce so more energy needs to be put into their design to make it work effectively.

Perfection is not and could not be a goal in order for the food chain web to work for long periods of time. Being good enough to be able to produce the next generation in a selected few and making a percentage of them that are contributing to predation requirements is how nature works.

On a planet that recycles energy in order to sustain its living organisms by consuming other living organisms is the main mechanism used on this planet. Perfecting all the organisms would not support this method of recycling energy. There is no other option but to recycle energy through death.

Looking at the end result also shows the clumsiness and imperfection of the evolutionary process. The human appendix? The fact that our breathing and swallowing tubes have openings right nect to each other, so that death by inhaling food is common. Female reproductive distress. Most humans developing nasty back problems. etc. etc.

It is really, really easy to point out all sorts of ways the end result of evolution is imperfect. If there was, in fact, a deity designer who made humans, I would recommend he be drummed out of the engineers union for incompetence.

You are relying on chance mutations and you are relying on elments of chance in the selection process. This is clumsy. I do not see how you can defend any other position.

I defend the predator/prey mechanism of why perfection is not selected. Chance mutations and relying on the elements of chance in the selection process seems to work just fine considering the offspring manage to be born without problems but later to fall due to predation.

Looking at the end result also shows the clumsiness and imperfection of the evolutionary process. The human appendix? The fact that our breathing and swallowing tubes have openings right nect to each other, so that death by inhaling food is common. Female reproductive distress. Most humans developing nasty back problems. etc. etc.

It is really, really easy to point out all sorts of ways the end result of evolution is imperfect. If there was, in fact, a deity designer who made humans, I would recommend he be drummed out of the engineers union for incompetence.

We have 7 billion people on the planet living just fine so no death by inhaling food is not common. Obviously a deity designer does not come into the equation of how life evolved, otherwise we would expect perfection in its creations.

You've reminded me of how reproduction is often contrived - against theories of fitness - to randomization. Why are women evolved so that the very fittest sperm of the pack has a 50% chance of going up the wrong tube? Why don't men evolve a smaller number of sperm, that are relatively huge endurance swimmers? Then selection would be a game of pure fitness. Why are flowering plants playing dice with pollinators?

You've reminded me of how reproduction is often contrived - against theories of fitness - to randomization. Why are women evolved so that the very fittest sperm of the pack has a 50% chance of going up the wrong tube? Why don't men evolve a smaller number of sperm, that are relatively huge endurance swimmers? Then selection would be a game of pure fitness. Why are flowering plants playing dice with pollinators?

Being a good swimmer doesn't gaurantee the most fit genes. Pure fitness requires more energy and since nature appears to have a limit in how much energy an individual is allowed, the disbursement is spread out to meet the basic needs of the organism.

There are answers to all those queries. Do you want to know them, or are they rhetorical questions only?

I'm saying if you roll these questions into one, the picture is of reproduction seemingly contrived to *ensure* 99% failure. And very often the factors employed to self-select are blindly arbitrary and irrelevant to "fitness" in a useful sense. Isn't it curious that a species would spend much energy constructing a dumb-luck lottery to filter its genes through?

Isn't it curious that a species would spend much energy constructing a dumb-luck lottery to filter its genes through?

All reproduction and 'fitness' issues are apparently dumb-luck from the perspective of any given individual at any point on the path. If you look at all those cute little turtles skittering to the sea, you know perfectly well that barely 1% of them will survive to get back and lay their own eggs. From natural systems point of view, all the 'failures' are a good source of protein for a wide variety of predators. And for all deaths, whether reptile, mammal or fungi, the constituent parts of the organism are useful to any number of other organisms.

For humans, I don't see the 'surprising' question. Lots of women and even more children die or are permanently injured during childbirth in current and historical circumstances lacking modern medical support or sophisticated midwifery. (And no comments about the age-old wisdom of communities. It's another matter of mere dumb-luck if you happen to be born in a place where community 'wisdom' does some real rather than imagined good.) Given the complexity and interdependence of our physical and mental functioning, I don't see any other way.

It's a constant process of cooperative, reinforcing processes with tradeoffs and limitations, all of which come together for a good or bad, wonderful or dreadful outcome. And remember, it's not just the birth the mother and child have to survive unharmed. They also have to get through the next year or so with a diet for the mother adequate to feed the child and maintain her own health. More cooperation, more tradeoffs. And they both have to survive any contagious disease that races through their community.

I think modern people, insulated from the vagaries of good & poor seasons on the land, and well-sheltered and clothed as well as medically shielded by vaccination from the ravages of measles or whooping cough, simply forget just how fragile human life really is.

When you look at life expectancy tables from history, they do not mean that people lived short, miserable lives and died before they were 40. What they mean is that many, many people, lots and lots of people, didn't live until their first, fifth or 15th birthdays. It was quite possible, not uncommon but always sad, for women to bear 8 or more children and never see even the possibility of a grandchild because none of them lived to adulthood. Those vast numbers of people with very, very short lifespans distort the average downwards.

Just remember one simple length-of-life fact. The longer you live, the longer you're likely to live.

Our young are just as vulnerable, if not more so, as the young of any other mammal. And human women are definitely in more danger during childbirth than any other mammal. It's only protection from food scarcity and contagious disease as well as good shelter and clothing that allows us to see almost 100% of our children survive to adulthood. We think of children's funerals as rare and 'wrong'. "A parent shouldn't have to bury a child." Until very few generations ago, children's funerals were frequent, and during epidemics they were the majority of deaths.

"Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill"nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke

Isn't it curious that a species would spend much energy constructing a dumb-luck lottery to filter its genes through?

All reproduction and 'fitness' issues are apparently dumb-luck from the perspective of any given individual at any point on the path. If you look at all those cute little turtles skittering to the sea, you know perfectly well that barely 1% of them will survive to get back and lay their own eggs. From natural systems point of view, all the 'failures' are a good source of protein for a wide variety of predators. And for all deaths, whether reptile, mammal or fungi, the constituent parts of the organism are useful to any number of other organisms.

For humans, I don't see the 'surprising' question. Lots of women and even more children die or are permanently injured during childbirth in current and historical circumstances lacking modern medical support or sophisticated midwifery. (And no comments about the age-old wisdom of communities. It's another matter of mere dumb-luck if you happen to be born in a place where community 'wisdom' does some real rather than imagined good.) Given the complexity and interdependence of our physical and mental functioning, I don't see any other way.

It's a constant process of cooperative, reinforcing processes with tradeoffs and limitations, all of which come together for a good or bad, wonderful or dreadful outcome. And remember, it's not just the birth the mother and child have to survive unharmed. They also have to get through the next year or so with a diet for the mother adequate to feed the child and maintain her own health. More cooperation, more tradeoffs. And they both have to survive any contagious disease that races through their community.

I think modern people, insulated from the vagaries of good & poor seasons on the land, and well-sheltered and clothed as well as medically shielded by vaccination from the ravages of measles or whooping cough, simply forget just how fragile human life really is.

When you look at life expectancy tables from history, they do not mean that people lived short, miserable lives and died before they were 40. What they mean is that many, many people, lots and lots of people, didn't live until their first, fifth or 15th birthdays. It was quite possible, not uncommon but always sad, for women to bear 8 or more children and never see even the possibility of a grandchild because none of them lived to adulthood. Those vast numbers of people with very, very short lifespans distort the average downwards.

Just remember one simple length-of-life fact. The longer you live, the longer you're likely to live.

Our young are just as vulnerable, if not more so, as the young of any other mammal. And human women are definitely in more danger during childbirth than any other mammal. It's only protection from food scarcity and contagious disease as well as good shelter and clothing that allows us to see almost 100% of our children survive to adulthood. We think of children's funerals as rare and 'wrong'. "A parent shouldn't have to bury a child." Until very few generations ago, children's funerals were frequent, and during epidemics they were the majority of deaths.

I would also add the invention of antibiotics gave us a tremendous advantage to surviving past childhood and later to old age since many of us would have died due to common infections that plague society. I know personally that I would have died from a simple urinary tract infection that I have had many times in my life. The tradeoff is that natural selection is not working effectively in our species since so many people didn't die due to modern advantages and are reproducing offspring that have so many ailments or health issues that are not being filtering out to natural selection.