OUT OF AFRICA THEORY AND EARLY MODERN HUMANS
There are various theories describing how migration patterns played a part in the development of early humans. The traditional, widely-accepted "Single Origin, Out of Africa Theory" of human evolution posits that: 1) earliest hominids evolved in Africa; 2) Australopithecus species evolved into Homo species in Africa; 3) early Homo species migrated to Asia and the Old World from Africa between a million and two million years ago; and 4) Homo sapiens also evolved in Africa and migrated outward from there.
The traditional "Out of Africa" theory holds that there were two migration of African-originating species. First, Homo erectus began slowly moving into the Middle east, Europe and Asia around 1.8 million years ago. And second, Homo sapiens began migrating into the same areas starting around 100,000 year ago. Scientists that uphold this theory argue that all modern humans have evolved from African Homo sapiens.
Charles Q. Choi wrote in Live Science: “Modern humans expanded out of Africa, spreading rapidly across most of the world's lands to colonize all continents except Antarctica, reaching even the most remote Pacific islands. A number of scientists conjecture this migration was linked with a mutation that transformed our brains, leading to our modern, complex use of language and enabling more sophisticated tools, art and societies. The more popular view suggests hints of such modern behavior existed long before this exodus, and that humanity instead had crossed a threshold in terms of population size in Africa that made such a revolution possible.” [Source: Charles Q. Choi, Live Science, February 22, 2011]
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “Unraveling the first migrations of anatomically modern humans out of Africa has invoked great interest among researchers from a wide range of disciplines. Available fossil, archeological, and climatic data offer many hypotheses, and as such genetics, with the advent of genome-wide genotyping and sequencing techniques and an increase in the availability of ancient samples, offers another important tool for testing theories relating to our own history. In this review, we report the ongoing debates regarding how and when our ancestors left Africa, how many waves of dispersal there were and what geographical routes were taken.” [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016]
Websites and Resources on Hominins and Human Origins: Smithsonian Human Origins Program humanorigins.si.edu ; Institute of Human Origins iho.asu.edu ; Becoming Human University of Arizona site becominghuman.org ; Talk Origins Index talkorigins.org/origins ; Last updated 2006. Hall of Human Origins American Museum of Natural History amnh.org/exhibitions ; Wikipedia article on Human Evolution Wikipedia ; Evolution of Modern Humans anthro.palomar.edu ; Human Evolution Images evolution-textbook.org; Hominin Species talkorigins.org ; Paleoanthropology Links talkorigins.org ; Britannica Human Evolution britannica.com ; Human Evolution handprint.com ; National Geographic Map of Human Migrations genographic.nationalgeographic.com ; Humin Origins Washington State University wsu.edu/gened/learn-modules ; University of California Museum of Anthropology ucmp.berkeley.edu; BBC The evolution of man" bbc.co.uk/sn/prehistoric_life; "Bones, Stones and Genes: The Origin of Modern Humans" (Video lecture series). Howard Hughes Medical Institute.; Human Evolution Timeline ArchaeologyInfo.com ; Walking with Cavemen (BBC) bbc.co.uk/sn/prehistoric_life ; PBS Evolution: Humans pbs.org/wgbh/evolution/humans; PBS: Human Evolution Library www.pbs.org/wgbh/evolution/library; Human Evolution: you try it, from PBS pbs.org/wgbh/aso/tryit/evolution; John Hawks' Anthropology Weblog johnhawks.net/ ; New Scientist: Human Evolution newscientist.com/article-topic/human-evolution;
Websites and Resources on Neanderthals: Wikipedia: Neanderthals Wikipedia ; Neanderthals Study Guide thoughtco.com ; Neandertals on Trial, from PBS pbs.org/wgbh/nova; The Neanderthal Museum neanderthal.de/en/ ; The Neanderthal Flute, by Bob Fink greenwych.ca. Websites and Resources on Prehistoric Art: Chauvet Cave Paintings archeologie.culture.fr/chauvet ; Cave of Lascaux archeologie.culture.fr/lascaux/en; Trust for African Rock Art (TARA) africanrockart.org; Bradshaw Foundation bradshawfoundation.com; Australian and Asian Palaeoanthropology, by Peter Brown peterbrown-palaeoanthropology.net. Fossil Sites and Organizations: The Paleoanthropology Society paleoanthro.org; Institute of Human Origins (Don Johanson's organization) iho.asu.edu/; The Leakey Foundation leakeyfoundation.org; The Stone Age Institute stoneageinstitute.org; The Bradshaw Foundation bradshawfoundation.com ; Turkana Basin Institute turkanabasin.org; Koobi Fora Research Project kfrp.com; Maropeng Cradle of Humankind, South Africa maropeng.co.za ; Blombus Cave Project web.archive.org/web; Journals: Journal of Human Evolution journals.elsevier.com/; American Journal of Physical Anthropology onlinelibrary.wiley.com; Evolutionary Anthropology onlinelibrary.wiley.com; Comptes Rendus Palevol journals.elsevier.com/ ; PaleoAnthropology paleoanthro.org.
Out of Africa, Multiregional and Assimilation Models
Charles Q. Choi wrote in Live Science: “The most bitterly debated question in the discipline of human evolution is likely over where modern humans evolved. The out-of-Africa hypothesis maintains that modern humans evolved relatively recently in Africa and then spread around the world, replacing existing populations of archaic humans. The multiregional hypothesis contends that modern humans evolved over a broad area from archaic humans, with populations in different regions mating with their neighbors to share traits, resulting in the evolution of modern humans. The out-of-Africa hypothesis currently holds the lead, but proponents of the multiregional hypothesis remain strong in their views.”[Source: Charles Q. Choi, Live Science, February 22, 2011]
Chris Stringer wrote in The Guardian: The idea of multiregional evolution” is ”an updated version of ideas from the 1930s. It envisaged deep parallel lines of evolution in each inhabited region of Africa, Europe, Asia and Australasia, stretching from local variants of H. erectus right through to living people in the same areas today. These lines did not diverge through time, since they were glued together by interbreeding across the ancient world, so modern features could gradually evolve, spread and accumulate, alongside long-term regional differences in things like the shape of the face and the size of the nose. [Source: Chris Stringer, The Guardian, June 19, 2011]
“The assimilation model “took the new fossil and genetic data on board and gave Africa a key role in the evolution of modern features. However, this model envisaged a much more gradual spread of those features from Africa than did mine. Neanderthals and archaic people like them were assimilated through widespread interbreeding. Thus the evolutionary establishment of modern features was a blending process rather than a rapid replacement.”
Migration of haplogroups ADN-Y
Out of Africa Theory and Homo Sapiens
Modern humans first arose at least 300,000 years ago in Africa, with oldest modern human fossils, from Morocco, dated to 300,000 years ago. Where the first modern humans originated and how they crossed the Sahara and dispersed from Africa has long been controversial. Earlier research suggested the migration from Africa started between 70,000 and 40,000 years ago. A study published in the mid 2010s suggested that modern humans might have begun their migration to Asia and Europe as early as 130,000 years ago, and expanded out of Africa in multiple waves. [Source: Charles Q. Choi, Live Science, May 28, 2015]
Some scientists believe that modern humans developed from archaic homo sapiens that migrated out of Africa about 100,000 years ago, replacing older homo species (archaic homo sapiens ) . Others argue that modern humans evolved out from Homo erectus populations in different parts of the world with some genetic exchange between groups.
DNA studies show that the group that became Africans and the group that became non-Africans split apart 189,000 years ago, much earlier than it was thought that non-Africans left Africa. According to DNA evidence the first group of hominids that left Africa had less than 50 members.
The warmest period of the last major interglacial period was around 125,000 years ago, when sea levels were 20 to 30 feet higher than they are today. Areas of Africa, the Middle East and West Asia that are desert today were covered by tropical deciduous forests and savannas dotted with numerous lakes. These habitats may have provided corridors for early Homo sapiens to migrate out of Africa.
The oldest confirmed fossils of modern humans are 300,000 years old from North Africa and 40,000 years old from Asia and Europe. Tool evidence pushes the dates further back in time. DNA studies back the Out of Africa Theory. The most conclusive are based on samples of mitochondrial DNA taken from more than a thousand men all over the world. Mitochondrial DNA is passed down from generation to generation by men in the Y chromosome. It shows that the further ethnic groups are from Africa the more different they are. Based on mitochondrial DNA data people today from Sudan, Ethiopia and Southern Africa are the closest lineal descendants of the first homo sapiens. Additionally, the fact that people of African descent have a greater of variation of certain genes suggest that they had more time to develop these variation, which means people must have evolved in Africa first.
Single Dispersal from Africa
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: One “topic of ongoing controversy relates to whether the first modern humans to leave Africa were part of a unique dispersal event or whether in fact there were multiple waves of dispersal out of Africa to populate the rest of the world. A single dispersal model states that anatomically modern humans migrated out of Africa to the rest of Eurasia as a single wave exiting via a single route, whether North or South. As discussed previously, variants of the single dispersal model differ in their timing, for example, after 50,000 years ago with complete population replacement under the upper Paleolithic model, versus those postulating as early as 100,000–125,000 years ago based on the Skhul and Qafzeh remains and climatic data. They also differ on the exact route taken, for example, single coastal dispersal models 50,000–75,000 years ago versus models governed by the location of discovered archeological artifacts, such as the Jebel Faya and Nubian models, based on artifacts found in present-day United Arab Emirates and North-East Africa, respectively. [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]
“Under all of these models, genetic evidence suggests that migration out of Africa was accompanied by a severe bottleneck in the initial migrating group(s), drastically reducing the genetic diversity before a rapid expansion. The serial founder effect model is one possible description of a single dispersal model, by which the dispersal out of Africa occurred initially via a single migrant group and continued in an iterative way as individuals dispersed into unoccupied regions, expanded in population size, and gave rise to new groups of founder individuals who again expanded into unoccupied areas. This serial founder process could give rise to the patterns of increasing genetic drift and decreasing genetic diversity observed in groups as geographic distance from Africa increases. ~
“However, recent work by Pickrell and Reich has shown that the inverse correlation observed between heterozygosity and geographic distance can be generated under further historical models that all deviate in some way from the serial founder effect model and yet not as extreme as the multiple dispersals model. Primarily, they present models of dispersal characterized by fewer bottlenecks and more pervasive admixture that can also account for the patterns of heterozygosity we see in global populations. ~
“East Asia is a key region when considering the nature of the first modern human dispersals. Under a single dispersal model, the peopling of East Asia is hypothesized to have occurred via a single wave, with, for example, Aboriginal Australians surmised to have diversified from within this East Asian wave of individuals. Recent whole-genome studies reveal a split between Europeans and Asians dating to 17,000–43,000 years ago, which seems in conflict with archeological evidence from greater Australia (Australia and Melanesia, including New Guinea), suggesting the presence of Anatomically modern human occupation in this region around 50,000 years ago. This evidence casts doubt on the single wave dispersal framework, as it has been suggested that this would allow insufficient time for Anatomically modern humans to have migrated to greater Australia. Addressing this idea, Wollstein et al investigated several dispersal hypotheses relating to the colonization and demographic history of Oceania. Using dense SNP array data and by simulating different demographic models for the occupation of this region, they found that the most parsimonious scenario involved a split of New Guineans from a common Eurasian ancestor population, rather than a separate early migration event. ~
Multiple Dispersals from Africa
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “Lahr and Foley were the first to propose that anatomically modern humans populated the world via multiple rather than a single wave of expansion from a morphologically variable population in Africa. Under their multiple dispersals model, there was an initial dispersal between 50 and 100,000 years ago through South Arabia to Southeast Asia (the Southern route) and a second migration following the Northern route, through the Levant, that led to the colonization of the rest of Eurasia between 40,000 and 50,000 years ago. They suggested that each of these dispersals was different in terms of the associated artifacts, with the first migration into the Arabian Peninsula affiliated with Middle Paleolithic stone tools and the later expansion through the Levantine corridor into Europe consistent with the appearance of upper Paleolithic tools. Later work by Field and Lahr used a geographical information system-based model, incorporating climatic data from 74,000 to 59,000 years ago, to show that both a Northern and a Southern route out of Africa would have been possible given environmental barriers. [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]
“More recently, McEvoy et al tested the multiple dispersals hypothesis by applying a LD-based approach to ∼200,000 SNPs in 17 global populations. They estimated the split time between these populations using mathematical models that relate the split time to FST between populations and the effective population size (Ne) of populations, assuming a simple bifurcating tree model. By testing divergence times in West and East Eurasian populations simultaneously, they found evidence for a more complex Out of Africa scenario than that suggested by a single dispersal model. Namely, they demonstrated a significant difference in estimates of African/European and African/East Asian divergence times (40,000 and 36, 000 years ago, respectively). These dates are more recent than those previously proposed but nonetheless may indicate that Europe and East Asia were occupied by separate Anatomically modern human dispersals. The same technique was used in recent work to explore divergence times between Europe and Africa and Australo-Melanesia and Africa. The split time for European and East African populations (57,000–76,000 years ago) was again estimated to be somewhat more recent than that for East Asia and Africa (73,000–88,000 years ago), and significantly more recent than that between Australo-Melanesians and Africa (87,000–119,000 years ago) even after accounting for Denisovan introgression into the ancestors of Australo-Melanesians. According to the authors, this is again inconsistent with a single wave dispersal and suggests that Australo-Melanesian populations retain signals of an ancient divergence from Africa. This fits well with the discovery of artifacts associated with human colonization at the Huon Peninsula of Papuan New Guinea and the Mungo Man remains, the oldest Anatomically modern human found in Australia, dated at 40,000 years ago. ~
“Templeton stressed the importance of genetic interchange under a multiple dispersals scenario.149 His model suggests that ancestors of modern humans, some of which did not necessarily have Anatomically modern human features, expanded out of Africa many times during the Pleistocene and that these expansions were never sufficient to remove the genetic contributions of previous dispersals, resulting in interbreeding between dispersing groups rather than population replacement. Further support for this model was recently provided by Reyes-Centeno et al who used morphological data from Holocene human cranial samples found in Asia, in conjunction with genetic data, to evaluate models of modern human dispersals out of Africa.They concluded that a single dispersal model was likely too simplistic and, as with other studies, found that modern humans first went south upon leaving African and only later took the Northern route in a second expansion wave. Recently published work providing evidence for modern human introgression into the ancestors of East Asian Neanderthals 100,000 years ago also gives support for the multiple dispersals hypothesis. ~
“In the same vein, it has been suggested that some isolated Southeast Asian/Oceania populations, such as Papuans and Andamanese and Malaysian Negritos, represent relic populations of a first wave Out of Africa. Some of this evidence is in light of autosomal DNA studies that have indicated Southeast Asia was settled by multiple waves of peoples, the first most related ancestrally to modern day groups such as the Onge and the second more closely related ancestrally to modern day East Asians. However, it remains challenging to disentangle whether differences in inferred ancestry are the result of long-term physical isolation and low population sizes rather than a separate wave of Out of Africa migration. ~
“Genetic evidence for an early Southern exit was presented by Rasmussen et al who analyzed a lock of hair from a 100-year-old Australian Aborigine. Applying D statistics to segregating sites in the genomes of modern Africans, Europeans, and Asians, they provided evidence for an early branching of Australian Aborigines 75,000–62,000 years ago. These results suggest that the ancestors of Australian Aborigines are some of the best modern day representatives of a possible early human dispersal into East Asia, although such a conclusion is still a matter of controversy. ~
“Opponents of an early migration into Australia and Oceania assert that if an early migration had taken place before Anatomically modern humans spread into Eurasia, then we would not expect to see evidence of Neanderthal admixture in these genomes given our current understanding of the Neanderthal geographic range. A conciliatory explanation for the fact that Australo-Melanesians have similar levels of Neanderthal admixture as other non-African populations has been proposed by Weaver, who has speculated that the Neanderthal genetic component present in Australasians may be the result of introgression from another group that was in direct contact with Neanderthals. ~
Out of Africa and Back Again
Genetic analysis of a skull in Romania suggests that a group of early humans may have returned to the continent, leaving their mark on people there today. Bill Condie wrote: A new study of two teeth from a 35,000-year-old woman found in Pestera Muierii cave in Romania, show that at least some humans returned to the African continent. [Source: Bill Condie, Cosmos, May 21, 2016 ***]
“The discovery, published in the journal Scientific Reports, could explain why today’s North Africans are genetically related to people from Europe and Asia, as well as to other Africans. Scientists from the University of the Basque Country and University of Uppsala studied the mitochondrial genome of the Pestera Muierii woman, known as PM1. They found she belonged to a genetic group, or haplotype, called Basal U6 – one that many modern North Africans have descended from. ***
“Analyses of present-day human mitogenomes suggest that some populations initiated a migration back to North Africa around 45,000 years ago. However, the scarcity of remains in North Africa has prevented researchers from obtaining direct evidence of such a migration. "It was very surprising and interesting to find an individual this old carrying a U6 haplotype," Emma Svensson of the University of Uppsala told reporters. "Since the U6 haplogroup today is most common in North African populations we didn't expect to find it in such an ancient human from Romania."” ***
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “Another major difficulty in using DNA from modern individuals to the study of Out of Africa migrations is the high proportion of non-African ancestry in modern-day Africans. The first indicators of what is termed the “back to Africa” migrations were obtained from phylogeny and phylogeography of mtDNA haplogroups U6 and M1, which have an origin outside Africa and are currently largely distributed within North and East Africa. [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]
“There is now robust evidence for recent migrations back to Africa from non-African populations, as exemplified by high levels of non-African ancestry in present-day Horn of Africa (Ethiopia, Eritrea, Djbouti, and Somalia) and Southern Africa, where Eurasian ancestry proportions can be as high as 40%–50% in, for example, some Ethiopian populations. What is less clear, however, is both the number and the timing of these migrations, as there seems to be a lack of consensus among archeological, mtDNA, Y chromosome, and genomic studies. Using genome-wide data, back to Africa admixture into the Horn of Africa was dated using special software programs to around 3,000 years ago, coinciding with the origin of the Ethiosemitic languages. Others have argued for older, perhaps additional, back to Africa migrations using both autosomal and mtDNA analyses. Any such admixture complicates the ability to study the Out of Africa hypothesis using the genomes of modern day groups. For example, it is plausible that Eurasian gene flow into Africa, together with the high genetic drift reported for East Asians compared to Europeans, might explain the reduced African/European compared to African/East Asian divergence times mentioned in the previous work supporting multiple dispersals out of Africa. ~
“Intriguingly, the genome of a 4,500-year-old Ethiopian individual (thus predating the 3,000 years ago Eurasian backflow) named Mota has recently been published. Given that this specimen represents the first aDNA sample from Africa, it will likely become crucial for understanding African genetic diversity and accounting for confounding factors when using DNA from modern populations to reconstruct ancient events. However, the power to draw precise inference from a single such sample is likely limited, so that any resulting conclusions should be treated with caution.” ~
Candelabra Versus Multiregional Hypothesises
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “The debate dominating much of the anthropological discourse throughout the second half of the 20th century focused on where and when archaic hominins evolved into modern Homo sapiens, which we refer to as anatomically modern humans (AMH) throughout. Two main hypotheses dominated the discourse: the multiregional and the replacement hypotheses. The original multiregional model was proposed by the anthropologist Weidenreich in 1946 and advocated significant gene flow among subpopulations of Homo erectus living in different parts of the globe throughout the Pleistocene, so that modern humans trace their ancestry to multiple hominin groups living in multiple regions. Confusingly, the term “multiregional” model often has been used synonymously with the so-called candelabra model, originally proposed by Coon in 1962. [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]
“The candelabra model hypothesizes that our early hominin ancestors, after leaving Africa 1 million years ago and migrating to other continents, independently evolved anatomically modern features. Under this model, the modern human form arose autonomously at multiple times and locations worldwide within the last 1 million years, so that modern non-African populations each primarily descended from separate evolutions of these Homo species. This is in contrast to the traditionally proposed multiregional model, which importantly does not propose independent parallel evolution of Anatomically modern humans features. ~
“The main fossil evidence in support of the multiregional and candelabra hypotheses was the discovery of the Dali Man in China. For multiregionalists or candelabra supporters, the mixture of archaic and modern features was evidence of a midway stage between early and modern hominins. That said, these fossils are poorly preserved, and some authors have suggested that these anatomical characteristics are in fact shared by other Homo worldwide, and thus were not unique to Asia. Some genetic studies also offered support to a multiregional and candelabra models, inferring the origin of a few genetic loci outside of the African continent. Examples include the oldest haplotype in the human dystrophin gene, which was found to be absent in Africans, although this was later explained as resulting from adaptive introgression from Neanderthals rather than providing support for the candelabra model.” ~
Candelabra Versus Replacement (Out of Africa) Hypothesis
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “Opposition to the candelabra hypothesis has come from both paleontological and genetic studies. The replacement, or out of Africa (OoA), model proposes a single and relatively recent transition from archaic hominins to Anatomically modern humans in Africa, followed by a later migration to the rest of the world, replacing other extant hominin populations. Under this model, these hominins were driven to extinction, so that most of the genetic diversity in contemporary populations descends from a single or multiple groups of Anatomically modern humans who spread out of Africa sometime in the last 55,000–200,000 years, although debate remains on the precise timings (note that, in light of admixture from extinct hominin groups, the Out of Africa model is consistent with the original multiregional model but not the candelabra model). [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]
“The first genetic evidence consistent with the Out of Africa model was provided by the study of mitochondrial DNA (mtDNA) phylogenetic trees, which identified Africa as the source of human mtDNA gene pool. It was shown that all mtDNA haplogroups outside of Africa can be attributed to either the M or N haplogroups, which arose around 60,000–65,000 years ago in South Asia and are thought to descend from the L3 haplogroup postulated to have arisen in East Africa around 80,000 years ago. This was supported by further studies of mtDNA, Y chromosome, and autosomal regions that suggested the existence of a common African ancestor. More recently, multilocus studies of genome-wide data have demonstrated that genetic diversity decreases as a function of geographic distance from East or South Africa, for example, as shown by an approximately linear decrease in heterozygosity and increase in linkage disequilibrium (LD), a finding consistent with the Out of Africa model. ~
“Several further replacement models exist, which differ in their emphasis. Harding and McVean, for example, proposed a more complex meta-population system for the origins of the first Anatomically modern humans. The authors highlight evidence suggesting that the ancestral African population from which modern humans arose was genetically structured, so that extant populations at the time contributed unequally to the gene pool of individuals migrating out of the continent. The effects of ancient population structure on patterns of modern day genetic variation have also been suggested in several more recent papers, which assess the impact of ancient hybridization on modern day genetic diversity through modeling and data-driven analyses. In addition to genetic studies, structure in the ancestral African population has also been supported through archeological and palaeoenvironmental models. ~
Timing of Out of Africa
Modern humans first arose at least 300,000 years ago in Africa. When and how they dispersed from there has been controversial and a topic of fierce debate in the academic community, with geneticists suggesting the exodus started between 40,000 and 70,000 years ago but fossils, artifacts and archaeological evidence saying they left much earlier than that. Many scientists believe that Homo sapiens began migrated out of Africa between 50,000 and 150,000 years ago, replacing species that evolved from Homo erectus , including perhaps Neanderthals. There is strong evidence they reached Australia, at least by 65,000 years ago. A burial site that age has been found there.
Katherine Sharpe wrote in Archaeology: For years, archaeologists and geneticists have been troubled by the fact that their time lines for key events in human evolution don’t always match up. While archaeologists rely on the dating of physical remains to determine when and how human beings spread across the globe, geneticists use a DNA “clock” based on the assumption that the human genome mutates at a constant rate. By comparing differences between modern and ancient DNA, geneticists then calculate when early humans diverged from other species and when human populations formed different genetic groups. [Source: Katherine Sharpe, Archaeology, December 17, 2012 +||+]
“The DNA clock is a powerful tool, but its conclusions—for example, that modern humans first emerged from Africa about 60,000 years ago—can disagree with archaeological evidence that shows signs of modern human activity well before that date at sites in regions as far-flung as Arabia, India, and China.” A “revised clock also supports archaeological signs of modern human activity from more than 60,000 years ago at sites such as Jwalapuram, India and Liujiang, China—evidence that has often been dismissed by geneticists as impossible. While more work is needed to confirm the findings, Scally says that archaeologists who work on such sites should be excited: “It can no longer be said that the genetic evidence is unequivocally against them.”“ +||+ Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “Currently, there are two conflicting proposals that dominate the literature, each differing by several tens of thousands of years and not mutually exclusive. The first claims that the Eurasian dispersal took place around 50,000 –60,000 years ago, reaching Australia by 45,000-50,000 years ago. The second posits that there was a much earlier exodus around 100,000 –130,000 years ago, prior to the eruption of Mount Toba (Northern Sumatra) dated to 74,000 years ago. [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]
“The Toba eruption is important in the context of dating the Out of Africa event, as stone tools thought to be associated with Anatomically modern humans have been found embedded in the volcanic ash. If these tools are indeed from anatomically modern humans, this provides clear evidence that modern humans had reached Southeast Asia before the Toba eruption more than 74,000 years ago. The stone tools discovered in the archeological site Jebel Faya (present-day United Arab Emirates) and the Nubian complex of Dhofar (present-day Oman) have provided further support for an early migration via Arabia. More importantly, the recent discovery of 47 human teeth in the Fuyan Cave in Daoxian (Southern China), dated to 80,000–120,000 years ago and unequivocally assigned to modern humans, supports the dispersal of Anatomically modern humans throughout Asia during the early Late Pleistocene. However, it remains to be seen if individuals among these groups contributed genetically to modern populations or represent another failed exodus similar to that proposed in the Levant, a question that DNA analyses are uniquely capable of shedding light on assuming genetic information can be interrogated reliably from these samples. Other pieces of archeological evidence that may help place Anatomically modern humans in the Far East over 70,000–120,000 years ago are the human remains from Zhirendong (South China), the teeth from Late Pleistocene Luna Cave, the famous Southern Chinese Liujiang skeleton, which seems to have anatomically modern features, and the Callao man, a human foot bone, discovered in Philippines that dates to 67,000 years ago.~
“Genetic studies have as yet been unable to settle the conflicting archeological evidence for these different dates, which can also be classified as pre-Toba (100,000–130,000years ago) or post-Toba (around 50,000–60,000 years ago). Given the lack of ancient DNA (aDNA) data temporally and spatially, such genetic-based approaches have focused on inference using modern DNA. Studies based on reconstructing mtDNA phylogenies have suggested a date for modern humans leaving Africa between 60,000-40,000 years ago, while dates inferred from STR analysis also fall within these estimates, positing an expansion date of around 50,000 years ago for central African, European, and East Asian populations. Time estimates from whole-genome sequencing data have been more variable and depend largely on the choice of model used. For example, studies using the allele frequency spectrum, identity-by-state, or coalescent-based models suggest a divergence time of 60,000–50,000 years ago, while analyses based on the pairwise sequencing Markovian coalescent (PSMC) model suggest that the divergence began 100,000–80,000 years ago, with gene flow occurring until 20,000 years ago. ~
“A key issue in the estimation of Out of Africa dates using autosomal data is that the Yoruba of West Africa are commonly used as the reference point for Anatomically modern human departure from East Africa, despite mtDNA and autosomal studies indicating a deep time separation of West and East African populations. Furthermore, many approaches assume that modern human groups are related via a simple bifurcating tree, which is likely an over simplistic view of human history. Another fundamental problem with many of the estimates used to date divergence times is that they are highly dependent on the choice of mutation rate, which can be estimated using a wide number of different approaches that often yield disparate values. The accumulation of heritable changes in the genome has traditionally been calculated from the divergence between humans and chimpanzees at pseudogenes, assuming a divergence time of around 6–7 million years ago (phylogenetic mutation rate 2.5 × 10−8/base/generation). With the advent of deep sequencing, it is now possible to directly calculate the mutation rate among present-day humans from parent-offspring trios. Using this method, the mutation rate has been estimated at 1.2 × 10−8/base/generation, half of the phylogenetic mutation rate, thus doubling the estimated divergence dates of Africans and suggesting that events in human evolution have occurred earlier than suggested previously. More recently, Harris reported that the rate of mutation has likely not been stable since the origin of modern humans, revealing higher mutation rates (particularly in the transition 5 -TCC-3 to 5 -TTC-3 ) in Europeans relative to African or Asian populations thus suggesting it may be too simplistic to assume the mutation rate is consistent across different populations. In addition to this, there is also considerable uncertainty in terms of the effect of paternal age at time of conception in the mutation rate with respect to ancestral populations. Recent work has attempted to mitigate some of these difficulties by instead calibrating estimates against fine-scale meiotic recombination maps. Using eight diploid genomes from modern non-Africans, Lipson et al calculated a mutation rate of 1.61 ± 0.13 × 10−8, which falls between phylogenetic and pedigree-based approaches. ~
“aDNA is becoming another major tool in appropriate calibration of mutation rate estimates and is likely to greatly refine our understanding of population divergence times, as it allows direct comparison of present-day and accurately dated ancient human DNA. For example, Fu et al used 10 whole mtDNA sequences from ancient Anatomically modern humans spanning Europe and East Asia from 40,000 years ago to directly estimate the mtDNA substitution rates based on a tip calibration approach. Using an amended mitochondrial substitution rate of 1.57 × 10−8, they dated the last major gene flow between Africans and non-Africans to 95,000 years ago. Later work utilized high coverage aDNA from a 45,000-year-old western Siberian individual called Ust’-Ishim and a technique based on modeling the number of substitutions in relation to the PSMC inferred history, which led to slightly higher estimates of 1.3–1.8 × 10−8 per base per generation. It is likely that an increasing availability of ancient samples from different time periods will assist in further refining these estimates.” ~
Origin of Modern Humans: Eastern or Southern, or Northern Africa?
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “Although the African origin of anatomically modern human is now largely accepted, debate has continued over whether the anatomically modern form first arose in East, South, or North Africa. Support for an East African origin is provided by the discovery of the [second] oldest unequivocally modern human fossils to date in Ethiopia: the Omo I from Kibish first discovered by Richard Leakey in 1967 dated to 190,000 and 200,000 years ago and the Herto fossils dated to between 160,000 and 154,000 years ago. [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]
“Evidence for a Southern origin has largely been provided by genetic rather than archeological studies. Henn et al analyzed genomes from extant hunter-gatherers from sub-Saharan Africa: pygmies of central Africa, click-speaking populations of Tanzania in East Africa (Hazda and Sandawe), and the Khomani Bushmen of Southern Africa. Their analyses of LD and heterozygosity patterns suggested Southern hunter-gatherers were among the most genetically diverse of all human populations, lending support to a Southern African origin of anatomically modern humans.
“Schlebusch et al also considered patterns of LD in South Africa, observing the same high levels of genetic diversity, low levels of LD, and shorter runs of heterozygosity as mentioned in the previous studies. However, by incorporating additional samples throughout the rest of Africa, they showed that LD-based statistics fail to pinpoint a specific origin point, as LD levels were similarly low in other parts of the continent besides South Africa, indicating that different groups of individuals within different regions are important. This suggests that the population history within sub-Saharan Africa is likely too complex to localize the origins of H. sapiens using these approaches and available data. Similarly, Pickrell et al showed an ancient link between the Southern African Khoe-San and the Hadza and Sandawe of East Africa, suggesting that both Eastern and Southern Africa are equally consistent candidates as an origin locality of modern humans. ~
“A more recent study jointly analyzed paleo-climatic records and estimates of effective population size from the whole-genome sequences of five Khoe-Sans and one Bantu individual along with 420,000 Single Nucleotide Polymorphisms (SNPs) from worldwide groups. Although unable to resolve a Southern or Eastern origin, using coalescent-based modeling, they suggest that Southern African populations have had high effective population sizes throughout their history, which might result in lower levels of LD relative to other parts of Africa, irrespective of where Anatomically modern humans arose. This corresponds well with climatic records, which find that Western and central Africa were affected by a dry climate with increasing aridity, around 100,000 years ago, leading to a decline in the effective population size of West African populations (ancestors of the Bantu-speaking and non-African populations) but not vastly altering the effective size of South Africans (ancestors of the Khoe-San). The incorporation of climatic data has also been important in mtDNA analyses aiming to resolve a clear location of origin. In a paper focusing on the distribution of mtDNA haplogroups, Rito et al propose that the most recent common ancestor (MRCA) of modern mtDNA likely arose in Central Africa before splitting into Southern African groups such as the Khoe-San (L0) and central/East African groups (L1’6). This is in good agreement with the aforementioned autosomal studies, which postulated an early split between the Khoe-San and more Northern African populations, although they did not advocate a MRCA in Central Africa. ~
Up until recently, little focus has been given to North Africa as a potential origin point of the Anatomically modern human form, despite the discovery of early anatomically modern humans, Jebel Irhoud remains in Morocco dated to 160,000 years ago [and 300,000 years ago], Focus on the region changed with the publication of a revised Y chromosomal phylogenetic tree based on resequencing of male-specific regions of the Y chromosome from four relevant clades. The revised phylogeny found that the deepest clades were rooted in central and Northwest Africa, suggesting this region was more important than previously thought. Fadhlaoui-Zid et al went on to analyze both Y chromosome and genome-wide data from North Africa, the Middle East, and Europe. They found some evidence for a recent origin of human populations in North Africa but stressed how high levels of migration, admixture, and drift in North Africans make interpretation extremely challenging. ~
“It is important to note that many genetic-based approaches such as these are limited in their ability to answer questions of this nature given that extant human populations are likely poor representatives of populations residing in these regions during pre-Anatomically modern human time periods. For instance, populations can be quite mobile, and thus the geographic location of modern humans groups may differ from that of their ancestors in the past. Archeological and paleontological approaches, as well as DNA from ancient human remains, can go some way to guiding inference but are also limited given the scarcity of sites. For example, an origin of Anatomically modern humans in Western or central Africa cannot be ruled out but to our knowledge, there is currently no archeological data available to address this as a candidate region.” ~
World’s Oldest Modern Human Fossils Found in Morocco
Our concept of human origins was thrown for a major loop in 2017 with the announcement of the discovery of modern human fossils, dated to 300,00 years ago, about 100,000 years older than any other known remains of our species, Homo sapien, in an old mine on a desolate mountain in Morocco. Both the date of the fossils — skulls, limb bones and teeth from at least five individuals — and their location were surprises — “a blockbuster discovery.” [Source: Will Dunham, Reuters, June 8, 2017 ^]
Will Dunham of Reuters wrote: “The antiquity of the fossils was startling - a “big wow,” as one of the researchers called it. But their discovery in North Africa, not East or even sub-Saharan Africa, also defied expectations. And the skulls, with faces and teeth matching people today but with archaic and elongated braincases, showed our brain needed more time to evolve its current form. “This material represents the very root of our species,” said paleoanthropologist Jean-Jacques Hublin of Germany’s Max Planck Institute for Evolutionary Anthropology, who helped lead the research published in the journal Nature.
“Before the discovery at the site called Jebel Irhoud, located between Marrakech and Morocco’s Atlantic coast, the oldest Homo sapiens fossils were known from an Ethiopian site called Omo Kibish, dated to 195,000 years ago. “The message we would like to convey is that our species is much older than we thought and that it did not emerge in an Adamic way in a small ‘Garden of Eden’ somewhere in East Africa. It is a pan-African process and more complex scenario than what has been envisioned so far,” Hublin said. ^
“The Moroccan fossils, found in what was a cave setting, represented three adults, one adolescent and one child roughly age 8, thought to have lived a hunter-gatherer lifestyle. These were found alongside bones of animals including gazelles and zebras that they hunted, stone tools perhaps used as spearheads and knives, and evidence of extensive fire use. An analysis of stone flints heated up in the ancient fires let the scientists calculate the age of the adjacent human fossils, Max Planck Institute archaeologist Shannon McPherron said. ^
Genetic Evidence of the Out of Africa Theory of Modern Men
Chinese researchers Feng Zhang, Bing Su, Ya-ping Zhang and Li Jin wrote in an article published by the Royal Society: “ The ‘out of Africa’ hypothesis asserts that modern humans originate from an ancestral population in Africa, which expanded and spread out of Africa and completely replaced archaic human populations (H. sapiens or H. erectus) outside Africa (Cann et al. 1987; Wilson & Cann 1992). Some anthropologists have claimed that anthropological evidence in China supported a regional evolution from H. erectus to modern human (Wu 1988). However, the phylogenetic tree of human mtDNA variations suggested that the ancestor of modern humans came out of Africa (Cann et al. 1987). From then on, more and more genetic data have been accumulated, most of which supported the out of Africa hypothesis (e.g. Bowcock et al. 1994; Hammer 1995; Tishkoff et al. 1996; Chu et al. 1998; Quintana-Murci et al. 1999; Su et al. 1999; Ingman et al. 2000; Ke et al. 2001). [Source: “Genetic studies of human diversity in East Asia” by 1) Feng Zhang, Institute of Genetics, School of Life Sciences, Fudan University, 2) Bing Su, Laboratory of Cellular and Molecular Evolution, Kunming Institute of Zoology, 3) Ya-ping Zhang, Laboratory for Conservation and Utilization of Bio-resource, Yunnan University and 4) Li Jin, Institute of Genetics, School of Life Sciences, Fudan University. Author for correspondence (firstname.lastname@example.org), 2007 The Royal Society ***]
As the mtDNA data supporting the out of Africa hypothesis were formerly restricted to the control region and RFLP in the coding region, Ingman et al. (2000) utilized the complete mtDNA sequences of 53 humans of diverse origins in tracing human evolution. As before, the newly generated mtDNA phylogeny indicated an African origin of modern humans (Ingman et al. 2000). ***
By analysing the markers on NRYs in over 1000 male individuals, Underhill et al. (2000) constructed a parsimonious genealogy to trace the evolution of modern humans. According to the phylogenetic tree, all the tested men from outside Africa share the same mutation (M168), which arose in Africa between 35 000 and 89 000 years ago. There are three parallel mutations (M89, M130 and Y Alu polymorphism, YAP) downstream of M168. Ke et al. (2001) examined these markers in 12 127 men from 163 populations in Asia and found that every sample had inherited one of these markers. This finding indicates that all of them are descendants of a relatively recent common ancestor in Africa, which supports a complete replacement of local archaic populations by modern humans from Africa from the perspective of paternal lineages. ***
Migration of Early Modern Humans Out of Africa
DNA studies of people living today indicate that modern humans migrated from Eastern Africa to the Middle East, then Southern and Southeast Asia, then New Guinea and Australia, followed by Europe and Central Asia. Perhaps they didn't enter Europe because that region was dominated by Neanderthals. According to research by geneticist at the University of Cambridge in the mid 2000s all modern humans descend from a small number of Africans that left Africa between 55,000 and 60,000 years ago. Another DNA less reliable study determined that an intrepid group of 500 hominids marched out of Africa about 140,000 years ago and they are the ancestors to all modern people today. [Source: Guy Gugliotta, Smithsonian magazine, July 2008]
These studies are based on genetic variations found in different population groups. People in sub-Saharan Africa have more genetic variation than non-Africans. The number of people and the date for the 140,000 year figure was arrived by studying genetic variations in 34 populations around the world, coming up with a rate of genetic change and extrapolated back in time. The fact that people in sub-Saharan Africa have more genetic variation than non-Africa indicated humans that have lived in Africa have lived there longer than other people have lived in their homelands.
The earliest known mutation to spread outside Africa is M168, which developed about 50,000 years ago. It is found in all non-Africans. M9 is a marker common in Eurasians. It appeared in the Middle East or Central Asia about 40,000 years ago. M3 is a marker that developed among Asian people around 10,000 years ago and reached the Americas.
Based on genetic evidence gathered by National Geographic magazine and scientists from around the globe it has been determined that modern humans originated in southern Africa around 200,000 years ago and made to West Africa about 70,000 years ago and the Middle East about 50,000 years ago, advancing rapidly through southern and southeast Asia and reaching Australia also around 50,000 years ago but not reach East Asia and Siberia until 30,000 years ago and southern Europe until 20,000 years. From Siberia modern humans reached North America about 15,000 years ago and migrated southward reaching South America between 13,000 and 15,000 years ago. The group living today with the closest links to our 200,000-year-old ancestors in southern Africa are the Khoisan hunter-gatherers of southern Africa. [Source: National Geographic, November, 2009]
Some scientists feel the migration out of Africa was also accompanied by revolutions in behavior and technology such as more developed social networks and advanced tools and sophisticated language that gave them ability to prosper in new lands and in some cases drive out hominids that already lived there.
Migration Routes Out of Africa
Modern humans first arose at least 300,000 years ago in Africa. When and how they dispersed from there has been controversial and a topic of fierce debate in the academic community, with geneticists suggesting the exodus started between 40,000 and 70,000 years ago but fossils, artifacts and archaeological evidence saying they left much earlier than that. The currently accepted theory backed up archaeological evidence is that the exodus from Africa followed the “southern route” along Arabia's shores, or possibly through its now-arid interior. Genetic evidence — and some archaeological evidence — supports the “northern route” theory that they traveled through modern-day Egypt, Israel-Palestine to Europe and Asia.
Charles Q. Choi wrote in Live Science: “Scientists had suggested two routes for the exodus from Africa. One, known as the northern route, has humans exiting through what is now Egypt and Sinai. The other, the southern route, brought humans through what is now Ethiopia and Arabia. The available evidence for either migratory path remains inconclusive”. [Source: Charles Q. Choi, Live Science, May 28, 2015]
“The northern route as the preferred way from Africa is supported by the fact that all non-Africans possess DNA from Neanderthals, who were present along the northern route in the eastern Mediterranean at the time. This new finding is also in agreement with the recent discovery of modern human fossils in Israel close to the northern route that date to about 55,000 years ago. Although there is genetic and archaeological evidence that some people did take the southern route out of Africa, perhaps those people got no farther than Arabia, or left no genetic trace in modern Eurasians.”
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote:“ The consensus view is that if modern humans did exit Africa via a single dispersal, there were two possible routes (not mutually exclusive) at the time: a Northern route, through Egypt and Sinai, and a Southern route, through Ethiopia, the Bab el Mandeb strait, and the Arabian Peninsula. So far, neither archeological nor genetic evidence has been able to resolve this question with confidence.” [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016]
Northern Route Out of Africa
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “Some of the earliest remains of Anatomically modern humans anywhere outside of Africa, the Skhul and Qafzeh hominins, were found in the Levant (present-day Israel) and dated to 120 and 100,000–90,000 years ago, respectively. It has been suggested that these fossils represent an early exit of modern humans approximately 120,000 years ago, traveling across the Sinai Peninsula to the Levant. The next human remains found in the region include the Manot1 cranium, which was dated to around 55,000 years ago, demonstrating a considerable gap in the fossil record of Anatomically modern human occupation in the Levant. This, in conjunction with climatic records, indicating a global glacial period 90,000 years ago, has led some authors to suggest that if the first humans did exit early via the Levant they did not survive, and that the Skhul and Qafzeh hominins are the remnants of this failed exodus. Other authors emphasize the possibility that this group could have already left the Levant before the glacial period 90,000 years ago. That said, the recent presentation of archeological material, primarily stone tools and assemblages dated to 100,000–80,000 years ago, from an empty corner of the Arabian Peninsula suggests early settlements may have been widely distributed and that even if Skhul and Qafzeh do represent a failed exodus, it was broader and more complex than previously thought. [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]
“In addition to the evidence from the archeological and climatic record, genetic studies have also suggested some support for a Northern route. A study of Y chromosome haplogroup distributions together with 10 microsatellite loci and 45 binary markers in different African and Near Eastern populations found that the Levant was the most supported route for the primary migratory movements between Africa and Eurasia. In a more recent paper, Pagani et al sequenced the genomes of 100 Egyptians and 125 individuals from five Ethiopian ethnic groups (Amhara, Oromo, Ethiopian Somali, Wolayta, and Gumuz).64 After attempting to mask West Eurasian genetic components inherited via recent non-African admixture within the last 4,000 years ago, they showed that modern non-African haplotypes were more similar to Egyptian haplotypes than to Ethiopian haplotypes, thus suggesting that Egypt was the more likely route in the exodus out of Africa migration, assuming the efficacy of their masking procedure. However, as noted earlier, one limitation of such studies that analyze modern DNA is that extant populations may not be good representatives of past populations due to factors such as population replacement, migrations, admixture, and drift.” ~
Oldest Known Human Fossil Outside Africa Discovered in Israel
Hannah Devlin wrote in The Guardian: “A human upper jawbone fossil with several teeth and stone tools, dated to between 177,000 and 194,000 years old, were found in a cave in Israel, meaning that modern humans left Africa far earlier than previously thought, prompting scientists to rethink theories about earllu human migration. The fossil is almost twice as old as any previous Homo sapiens remains discovered outside Africa. [Source: Hannah Devlin, The Guardian, January 25, 2018 |=|]
“The fossil, a well-preserved upper jawbone with eight teeth, was discovered at the Misliya cave, which appears to have been occupied for lengthy periods. The teeth are larger than average for a modern human, but their shape and the fossil’s facial anatomy are distinctly Homo sapiens, an analysis of the fossil in the journal Science concludes. |=|
“Sophisticated stone tools and blades discovered nearby suggest the cave’s inhabitants were capable hunters, who used sling projectiles and elegantly carved blades used to kill and butcher gazelles, oryx, wild boars, hares, turtles and ostrich. The team also discovered evidence of matting made from plants that may have been used to sleep on. Radioactive dating places the fossil and tools at between 177,000 and 194,000 years old. “Hershkovitz said the record now indicates that humans probably ventured beyond the African continent whenever the climate allowed it. “I don’t believe there was one big exodus out of Africa,” he said. “I think that throughout hundreds of thousands of years [humans] were coming in and out of Africa all the time.” |=|
“Reconstructions of the ancient climate records, based on deep sea cores, show that the Middle East switched between being humid and extremely arid, and that the region would have been lush and readily habitable for several periods matching the age of the Misliya fossil.” |=|
177,000-Year-Old Israeli Human Fossils and Out of Africa Theory
Hannah Devlin wrote in The Guardian: “Until recently, several converging lines of evidence – from fossils, genetics and archaeology – suggested that modern humans first dispersed from Africa into Eurasia about 60,000 years ago, quickly supplanting other early human species, such as Neanderthals and Denisovans, that they may have encountered along the way. |=|
“However, a series of recent discoveries, including a trove of 100,000 year-old human teeth found in a cave in China, have clouded this straightforward narrative. And the latest find, at the Misliya cave site in northern Israel, has added a new and unexpected twist. “What Misliya tells us is that modern humans left Africa not 100,000 years ago, but 200,000 years ago,” said Prof Israel Hershkovitz, who led the work at Tel Aviv University. “This is a revolution in the way we understand the evolution of our own species.”
“The discovery also raises intriguing questions about the fate of the earliest modern human pioneers. Genetic data from modern-day populations around the world strongly suggest that everyone outside Africa can trace their ancestors back to a group that dispersed around 60,000 years ago. So the inhabitants of the Misliya cave are probably not the ancestors of anyone alive today, and scientists can only speculate why their branch of the family tree came to an end. |=|
“Prof David Reich, a geneticist at Harvard University and an expert in population genetics and ancient DNA, said: “It’s important to distinguish between the migration out of Africa that’s being discussed here and the “out-of-Africa” migration that is most commonly discussed when referring to genetic data. This [Misliya] lineage contributed little if anything to present-day people.” “These early exits are sometimes termed ‘unsuccessful’ or ‘failed’,” said Stringer. “Some of these groups could have gone extinct through natural processes, through competition with other humans, including later waves of modern humans, or they could have been genetically swamped by a more extensive 60,000 year old dispersal.” |=|
177,000-Year-Old Israeli Human Fossils and Multiple Migrations Out of Africa
Hannah Devlin wrote in The Guardian: “The find suggests that there were multiple waves of migration across Europe and Asia and could also mean that modern humans in the Middle East were mingling, and possibly mating, with other human species for tens of thousands of years. |=| “Misliya breaks the mould of existing scenarios for the timing of the first known Homo sapiens in these regions,” said Chris Stringer, head of human origins at the Natural History Museum in London. “It’s important in removing a long-lasting constraint on our thinking.” [Source: Hannah Devlin, The Guardian, January 25, 2018 |=|]
“The idea of multiple dispersals is supported by recent discoveries such as the teeth unearthed in China, human fossils in Sumatra from around 70,000 years ago, archaeological evidence from Northern Australia at 65,000 years and fossils previously discovered near Misliya dating to 90,000-120,000 years ago. The scenario also raises the possibility that the eastern Mediterranean may have acted as a crossroads for encounters between our own ancestors and the various other human species, such as Neanderthals, who had already reached Europe. “We’re like a train station that everyone’s passing through,” said Hershkovitz. |=|
“Scientists have already shown that interbreeding with Neanderthals, whose lineage diverged from our own 500,000 years ago, occurred some time in the past 50,000 years.As a legacy, modern-day Eurasians carry 1-4 percent of Neanderthal DNA. However, a recent analysis of DNA taken from a Neanderthal leg bone found in a German cave hinted at much earlier encounters between the two species, dating back more than 200,000 years. The new fossil adds plausibility to this theory. “It means modern humans were potentially meeting and interacting during a longer period of time with other archaic human groups, providing more opportunity for cultural and biological exchanges,” said Rolf Quam, Binghamton University anthropology professor and a co-author of the study.” |=|
DNA Study Supports Humans Leaving Africa Via Egypt on the Northern Route
DNA from Ethiopians and Egyptians suggests modern humans left Africa through Egypt. Charles Q. Choi wrote in Live Science: “To see which route the ancestors of all humans outside of Africa might have taken, the researchers sequenced the genomes of 225 people from northeast Africa — 100 Egyptians and 125 Ethiopians. They then compared this data with DNA from East Asians, South Asians and Europeans — specifically, Han Chinese, Gujarati Indians and Tuscan Italians, respectively. They also compared this data with DNA from modern West Africans from south of the Sahara, which should generally reflect the ancient sub-Saharan gene pool. [Source: Charles Q. Choi, Live Science, May 28, 2015]
“The scientists noted that both modern Egyptians and Ethiopians have recently experienced migrations from outside Africa, and the interbreeding that resulted might increase their genetic similarity with those migratory people. To account for this, the researchers removed any genetic sequences that might have come from these recent migrations. . The scientists detailed their findings online today (May 28) in the American Journal of Human Genetics.
“If the southern route was the main path out of Africa, Ethiopians should be more genetically similar to Eurasians. Instead, the researchers found that Egyptians were more genetically similar to Eurasians, suggesting the northern route was the predominant way out of Africa. The researchers estimated that Eurasians genetically diverged from Egyptians 55,000 years ago, Ethiopians 65,000 years ago and West Africans 75,000 years ago. "The most exciting consequence of our results is to have unveiled an episode of the evolutionary past of all Eurasians, therefore potentially improving the knowledge of billions of people on their deep biological history,"study lead author Luca Pagani, a molecular anthropologist at the Wellcome Trust Sanger Institute and the University of Cambridge in England, told Live Science.”
Cretan Tools Point to 130,000-Year-Old Sea Travel
Zach Zorich wrote in Archaeology magazine, “A research team led by Thomas Strasser of Providence College and Eleni Panagopoulou of the Greek Ministry of Culture announced the discovery of stone tools at two sites on the island of Crete that are between 130,000 and 700,000 years old. Rough axes and other tools, found close to shelters on the island's south coast, resemble tools made by Homo heidelbergensis and Homo erectus The tools were found during a survey of caves and rock shelters near the village of Plakias by archaeologists from the American School of Classical Studies at Athens and the Culture Ministry. "Up to now we had no proof of Early Stone Age presence on Crete," said senior ministry archaeologist Maria Vlazaki, who was not involved in the survey. She said it was unclear where the hominids had sailed from, or whether the settlements were permanent. "They may have come from Africa or from the east," she said. "
The stone tools found on of Crete may be evidence of one of the world's first sea voyages by human ancestors, the Greek Culture Ministry. They show that early human ancestors boated across at least 40 miles of open sea to reach the island, the earliest indirect evidence of seafaring. "If hominins could move around the Mediterranean before 130,000 years ago, they could cross other bodies of water as well," says team member Curtis Runnels of Boston University, who helped analyze the tools. "When similar finds on other islands are confirmed, the door will be opened to the re-evaluation of every assumption we have made about early hominin migrations." [Source: Zach Zorich, Archaeology magazine, January/February 2011]
AP reported: “Crete has been separated from the mainland for about five million years, so whoever made the tools must have traveled there by sea. That would upset the current view that human ancestors migrated to Europe from Africa by land alone. "The results of the survey not only provide evidence of sea voyages in the Mediterranean tens of thousands of years earlier than we were aware of so far, but also change our understanding of early hominids' cognitive abilities," the ministry statement said. [Source: AP, January 3 2011]
The previous earliest evidence of open-sea travel in Greece dates back 11,000 years (worldwide, about 60,000 years — although considerably earlier dates have been proposed).
Southern Route Out of Africa
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “In contrast, mtDNA studies have traditionally favored a Southern route across the Bab el Mandeb strait at the mouth of the Red Sea. From there, modern humans are thought to have spread rapidly into regions of Southeast Asia and Oceania. For example, two studies have concluded that individuals assigned to haplogroup L3 migrated out of the continent via the Horn of Africa. Furthermore, Fernandes et al. analyzed three minor West-Eurasian haplogroups and found a relic distribution of these minor haplogroups suggestive of ancestry within the Arabian cradle, as expected under a Southern route. That being said, many mtDNA studies, including these, are based on the premise that haplogroup L3 represents a remnant Eastern African haplogroup. Groucutt et al have recently theorized that L3 does not provide conclusive evidence for a shared African ancestor, given human demographic history is likely to be less “tree-like” than has been consistently assumed by mtDNA analyses. As an example, they showed that L3 could have arisen inside or outside of Africa if gene flow occurred between the ancestors of Africans and non-Africans following their initial divergence. [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]
“Short Tandem Repeats (STR) and analysis of LD decay in combination with geographic data have also been used to support a Southern route via a single wave serial bottleneck model. Under this model, it is thought that a group crossed the mouth of the Red Sea and traveled along the Southern coast of the Arabian Peninsula toward India as “beachcombers,” exploiting shellfish and other marine products. Migrations then continued in an iterative wave as populations dispersed and expanded into uninhabited areas. This is consistent with a glacial maximum occurring during this time period, which caused sea levels to fall allowing potential passage across the mouth of the Red Sea. ~
“From an archeological perspective, evidence indicative of maritime exploitation is extremely limited. The discovery of artifacts from the Abdur Reef Limestone in the Red Sea and archeological sites in the Gulf Basin that indicate long-standing human occupation earlier than 100, 000 years ago may offer some evidence; however, whether these represent the activities of the ancestors of modern-day human groups is still an open question. Furthermore, Boivin et al caution that while coastal regions may have been important, a coastal-focused dispersal would still have been problematic and not necessarily conducive to rapid out of Africa dispersal.” ~
Tools in Arabia Imply an Early African Migration Using the Southern Route
Stone tools found in United Arab Emirates, dated to between 125,000 and 55,000 years ago, resembles African artifacts from around the same time, suggesting that early humans left Africa earlier than thought. Mary Beth Griggs wrote in Discover:. According to project archaeologist Anthony Marks of Southern Methodist University, southern Arabia would not have been a forbidding destination at the time. “We now know that 130,000 years ago, the Indian Ocean monsoons pushed farther north, and Arabia became grassland,” says Marks, who thinks the shifting climate opened new territory for human exploration. Although some researchers suspect that earlier hominins, not modern humans, made the stone tools, Marks is hopeful that future digs in Arabia, Iran, and western India will unearth still more evidence of humanity’s bold, early route out of Africa. [Source: Mary Beth Griggs, Discover, December 22, 2011]
Ian Sample wrote in The Guardian: “A spectacular haul of stone tools discovered beneath a collapsed rock shelter in southern Arabia has forced a major rethink of the story of human migration out of Africa. The collection of hand axes and other tools shaped to cut, pierce and scrape bear the hallmarks of early human workmanship, but date from 125,000 years ago, around 55,000 years before our ancestors were thought to have left the continent. The artefacts, uncovered in the United Arab Emirates, point to a much earlier dispersal of ancient humans, who probably cut across from the Horn of Africa to the Arabian peninsula via a shallow channel in the Red Sea that became passable at the end of an ice age. Once established, these early pioneers may have pushed on across the Persian Gulf, perhaps reaching as far as India, Indonesia and eventually Australia. [Source: Ian Sample, The Guardian January 27, 2011 |=|]
“A team led by Hans-Peter Uerpmann at the University of Tübingen in Germany uncovered the latest stone tools while excavating sediments at the base of a collapsed overhang set in a limestone mountain called Jebel Faya, about 35 miles (55km) from the Persian Gulf coast. Previous excavations at the site have found artefacts from the iron, bronze and neolithic periods, evidence that the rocky formation has provided millennia of natural shelter for humans. The array of tools include small hand axes and two-sided blades that are remarkably similar to those fashioned by early humans in east Africa. The researchers tentatively ruled out the possibility of other hominins having made the tools, such as the Neanderthals that already occupied Europe and north Asia, as they were not in Arabia at the time. |=|
“The stones, a form of silica-rich rock called chert, were dated by Simon Armitage, a researcher at Royal Holloway, University of London, using a technique that measured how long sand grains around the artefacts had been buried. Another strand of the archaeologists' work, described in Science, focused on climate change records and historical sea levels in the area. They show that between 200,000 and 130,000 years ago, a global ice age caused sea levels to fall by up to 100 metres, while the Saharan and Arabian deserts expanded into vast, inhospitable wastelands. But as the climate warmed at the end of the ice age, fresh rains fell on Arabia, opening up the region to human occupation. "The previously arid interior of Arabia would have been transformed into a landscape covered largely in savannah grasses, with extensive lakes and river systems," said Adrian Parker, a researcher at Oxford Brookes University and co-author of the paper. |=|
“The revival of Arabia coincided with record lows in sea level, which left only a shallow stretch of water about three miles wide at the Bab al Mandab Straits separating east Africa and the Arabian peninsula. Uerpmann said early humans may have walked or waded across, but added: "They could have used rafts or boats, which they certainly could make at that time." The new arrivals would have found good hunting grounds at the end of their journey, with plentiful wild asses, gazelles and mountain ibex, Uerpmann said. |=|
“The discovery has sparked debate among archaeologists, some of whom say much stronger evidence is needed to back up the researchers' claims. "I'm totally unpersuaded," Paul Mellars, an archaeologist at Cambridge University, told Science. "There's not a scrap of evidence here that these were made by modern humans, nor that they came from Africa." Chris Stringer, a palaeontologist at the Natural History Museum in London, said: "The region of Arabia has been terra incognita in trying to map the dispersal of modern humans from Africa during the last 120,000 years, leading to much theorising in the face of few data. "Despite the confounding lack of diagnostic fossil evidence, this archaeological work provides important clues that early modern humans might have dispersed from Africa across Arabia, as far as the Straits of Hormuz, by 120,000 years ago." |=|
90,000-Year-Old Human Middle Finger Bone Found in Saudi Arabia
In 2016, archaeologists in Saudi Arabia announced the discovery of a human fossil bone — the middle section of the middle finger — which was dated to be 90,000 years old, the oldest evidence modern humans on the Arabian Peninsula, an official from the Saudi Commission for Tourism and National Heritage told Al-Arabiya. The Saudis claimed it was the oldest human bone ever found. [Source: Jack Moore, Newsweek, August 19, 2016 -]
Jack Moore wrote in Newsweek: “Researchers from a joint Saudi-U.K. project, which included the Saudi archaeologists and University of Oxford experts, made the find at the Taas al-Ghadha site near to the northwestern Saudi city of Tayma. The project is an extension of the Green Arabia Project, which is studying sites near ancient lakes in the Nafud desert. Archaeologists began digging in the area in 2012. -
“Its historic discovery suggests that human life dated back as far as 325,000 years, head of the Saudi Commission for Tourism and National Heritage Ali Ghabban said. He did not elaborate on why the find of a 90,000-year-old bone led to this assumption. The Board of the Saudi Commission for Tourism and National Heritage, said that the discovery is “considered an important achievement for the Saudi researchers who participated in these missions and one of the most important outcomes of Prince Sultan’s support and care for the archaeology sector in the Kingdom.” -
While the Saudis are claiming to have found the oldest ever human bone, the oldest bone ever discovered belonging to the lineage that developed into human beings, the Homo genus, is a jaw bone found in Ethiopia in 2015. It is dated to 2.8 million years ago. The oldest modern human discovered at that time was a 195,000-year-old fossil from Ethiopia. Since then 300,000-year-old modern human fossils have been found in Morocco.
Oman Artifacts Suggest Early Humans Traveled Inland in Arabia Rather Along the Coast
Charles Q. Choi wrote in Live Science: “More than 100 newly discovered sites in the Sultanate of Oman apparently confirm that modern humans left Africa through Arabia long before genetic evidence suggests. Oddly, these sites are located far inland, away from the coasts. "After a decade of searching in southern Arabia for some clue that might help us understand early human expansion, at long last we've found the smoking gun of their exit from Africa," said lead researcher Jeffrey Rose, a paleolithic archaeologist at the University of Birmingham in England. "What makes this so exciting is that the answer is a scenario almost never considered." [Source: Charles Q. Choi, Live Science, November 30, 2011 *]
“The international team of archaeologists and geologists made their discovery in the Dhofar Mountains of southern Oman, nestled in the southeastern corner of the Arabian Peninsula. "The coastal expansion hypothesis looks reasonable on paper, but there is simply no archaeological evidence to back it up," said researcher Anthony Marks of Southern Methodist University, referring to the fact that an exodus by the coast, where one has access to resources such as seafood, might make more sense than tramping across the desert.. *\
“The 100-to-200 artifacts they found there were of a style dubbed Nubian Middle Stone Age, well-known throughout the Nile Valley, where they date back about 74,000-to-128,000 years. Scientists think ancient craftsmen would have shaped the artifacts by striking flakes off flint, leading to distinctive triangular pieces. This is the first time such artifacts have been found outside of Africa. *\
“Subsequent field work turned up dozens of sites with similar artifacts. Using a technique known as optically stimulated luminescence dating, which measures the minute amount of light long-buried objects can emit, to see how long they have been interred, the researchers estimate the artifacts are about 106,000 years old, exactly what one might expect from Nubian Middle Stone Age artifacts and far earlier than conventional dates for the exodus from Africa. *\
“Finding so much evidence of life in what is now a relatively barren desert supports the importance of field work, according to the researchers. "Here we have an example of the disconnect between theoretical models versus real evidence on the ground," Marks said. However, when these artifacts were made, instead of being desolate, Arabia was very wet, with copious rain falling across the peninsula, transforming its barren deserts to fertile, sprawling grasslands with lots of animals to hunt, the researchers explained. "For a while, South Arabia became a verdant paradise rich in resources — large game, plentiful fresh water, and high-quality flint with which to make stone tools," Rose said. *\
“Instead of hugging the coast, early modern humans might therefore have spread from Africa into Arabia along river networks that would've acted like today's highways, researchers suggested. There would have been plenty of large game present, such as gazelles, antelopes and ibexes, which would have been appealing to early modern humans used to hunting on the savannas of Africa. "The genetic signature that we've seen so far of an exodus 70,000 years ago might not be out of Africa, but out of Arabia," Rose told LiveScience. *\
“So far the researchers have not discovered the remains of humans or any other animals at the site. Could these tools have been made by now-extinct human lineages such as Neanderthals that left Africa before modern humans did? Not likely, Rose said, as all the Nubian Middle Stone Age tools seen in Africa are associated with our ancestors. It remains a mystery as to how early modern humans from Africa crossed the Red Sea, since they did not appear to enter the Arabian Peninsula from the north, through the Sinai Peninsula, Rose explained. "Back then, there was no land bridge in the south of Arabia, but the sea level might not have been that low," he said. Archaeologists will have to continue combing the deserts of southern Arabia for more of what the researchers called a "trail of stone breadcrumbs." The scientists detailed their findings online November 30, 2011 in the journal PLoS ONE.” *\
Intermixing with Neanderthals and Denisovans
Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote:“On their migration out of Africa, Anatomically modern humans were not alone, with at least two distinct groups of archaic humans inhabiting Eurasia on their arrival: the Neanderthals and Denisovans. Traditionally, the replacement or the Out of Africa model assumed no intermixing between Anatomically modern humans leaving Africa and archaic hominins such as the Neanderthals. The revised replacement model, however, allows for gene flow with these archaic forms following the Out of Africa dispersal, which is also consistent with the original multiregional model proposed by Weidenreich but still differs from the candelabra model. [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]
“Some of the most exciting outcomes of work on aDNA have been the publication of full Neanderthal and Denisovan genomes. Neanderthals, named after Neander valley in Germany where the species was discovered, are thought to have first appeared 250,000–200,000 years ago, although the exact range is still under debate, and persisted, at least in regions of Southern Europe, until around 30,000 years ago. Initial genetic analyses focused on mtDNA, which is more easily extracted and amplified in ancient samples, and suggested no intermixing between Neanderthals and modern humans as they migrated into Eurasia. However, such analyses that rely on only single-locus data such as mtDNA can suffer from a lack of power. The first draft of the Neanderthal whole genome was published in 2010 where, in a landmark study, Green et al found that Neanderthals interbred with modern humans, contributing detectable segments of their genomes (1.5%–2.1%) to present-day populations outside of Africa. More recent estimates, based on mutation rate estimates refined by precise data for recombination rates as described previously, date this admixture to within 35,000–49,000 years ago. These new dates, which are more recent than previously published estimates,119 are in good agreement with recent work that suggested Neanderthal admixture with modern humans was not restricted to the time period of the Out of Africa migration in the Near East but instead may have also occurred more recently in Europe. Applying D statistics, which measure correlations in allele frequencies due to shared drift and/or admixture, to DNA extracted and enriched from the Oase 1 human mandible found in Romania and dated to 37,000–42,000 years ago, Fu et al found that 6%–9% of the Oase 1 genome was derived from Neanderthals. Analyzing the lengths of segments in Oase 1 of likely Neanderthal ancestry, they inferred that Neanderthal introgression into this individual occurred in the previous four to six generations (Fig. 1).123 The authors caution that Oase 1 likely did not contribute to modern humans but nonetheless it provides a striking example of relatively recent Neanderthal introgression. Interestingly, Kuhlwilm et al have recently provided evidence for modern human introgression into the ancestors of Neanderthals from the Altai Mountains 100,000 years ago in the Near East, although not in Europe, thus suggesting that a group of Anatomically modern humans might have left Africa before 100,000 years ago. This is also in agreement with the Daoxian remains, and other fossil remains described previously that helped place the Anatomically modern humans in East Asia in the early Late Pleistocene. ~
“Analysis of a hominin finger phalanx discovered at the Denisova Cave of the Altai Mountains in Southern Siberia confirmed the existence of a genetically distinct group of archaic humans related to Neanderthals, named the Denisovans. The Denisovan lineage was classified based on genetic evidence and estimated to have diverged genetically from Neanderthals 381,000–473,000 years ago assuming a simple bifurcating tree.109 One startling discovery was that despite being discovered and identified in Siberia, the Denisovan genome was found to share detectable segments of DNA (3%–5% of the genome) in common with modern-day Near Oceanians, including New Guineans, Australians, and Mamanwas (a Negrito group from the Philippines). Since then, Denisovan introgression has been detected in further populations, for example, those from East Eurasia and Native America, suggesting the extent of Denisovan ancestry in modern populations is likely more widespread than has been previously thought. There is some evidence that haplotypes associated with archaic human introgression have been maintained in modern groups as a result of them providing advantageous genetic variation. For example, a recent study proposes that a haplotype that is adaptive to hypoxic conditions in high altitude Tibetans has a structure consistent with introgression from a Denisovan or Denisovan-related individuals, suggesting that gene flow with other hominins may be important in human adaptation to local environments.” ~
See Separate Articles on Neanderthals and Denisovans
Modern Humans in Australia 65,000 Years Ago Challenges Migration Models
Fossils of similar age have been found in Asia but the oldest modern human fossils found in Europe are about 45,000 years old. This means that modern humans made its way its way from across Asia and took boats to Australia around 20,000 years before they traversed a much shorter distance to Europe. One explanation for the delay in occupying Europe is the presence of Neanderthals there.
Recently discovered archaeological evidence suggesting the first Australians arrived at least 65,000 years ago, Gemma Tarlach wrote, in Discover magazine, is “at odds with the conventional date for our species leaving Africa, and adds fuel to the growing bonfire of what was the evolutionary timeline for Homo sapiens. For decades, the hoary old story of human evolution and migration went something like this: An archaic version of Homo sapiens evolved in Africa around 200,000 years ago, and eventually amassed enough random advantageous mutations to get upgraded to version 2.0 (thanks, natural selection!), aka modern Homo sapiens, by about 100,000 years ago. Then, the timeline gets a bit iffy. Many paleoanthropologists had long argued that our species didn’t leave Africa until 60,000 years ago — some put the date even later, around 40,000 years ago. That’s what the archaeological evidence told them, and that’s what they stuck hard and fast to. [Source: Gemma Tarlach, Discover, July 19, 2017]
“Since the 1990s, however, a growing number of studies — increasingly driven by genetic evidence — have painted a very different picture of human evolution and migration. Most recently, in 2016 a landmark genomic study of 400 Papua New Guineans suggested that modern Homo sapiens may have arrived in the region 120,000 years ago. And earlier this month, the sequencing of ancient mitochondrial (maternally-inherited) DNA extracted from a Neanderthal femur hinted that African Homo sapiens were interbreeding with European Neanderthals more than 200,000 years ago.
“Then there was the announcement earlier this year that Homo sapiens — albeit not quite version 2.0 — were in Morocco 300,000 years ago — the best evidence yet that our species is considerably older than we thought. Enter The First Australians Question. As one of the corners of the world furthest-flung from Africa, it makes sense that our species would arrive there fairly late in its relentless march across the planet. Many old-schoolers believed humans first set foot in Australia anywhere from 20,000-40,000 years ago.
Humans in the Arctic 45,000 Years Ago?
Ann Gibbons wrote in Science: “In August of 2012, an 11-year-old boy made a gruesome discovery in a frozen bluff overlooking the Arctic Ocean. While exploring the foggy coast of Yenisei Bay, about 2000 kilometers south of the North Pole, he came upon the leg bones of a woolly mammoth eroding out of frozen sediments. Scientists excavating the well-preserved creature determined that it had been killed by humans: Its eye sockets, ribs, and jaw had been battered, apparently by spears, and one spear-point had left a dent in its cheekbone—perhaps a missed blow aimed at the base of its trunk. [Source: Ann Gibbons, Science, January 14, 2016 ^]
“When they dated the remains, the researchers got another surprise: The mammoth died 45,000 years ago. That means that humans lived in the Arctic more than 10,000 years earlier than scientists believed, according to a new study. The find suggests that even at this early stage, humans were traversing the most frigid parts of the globe and had the adaptive ability to migrate almost everywhere. ^
“Most researchers had long thought that big-game hunters, who left a trail of stone tools around the Arctic 12,500 years ago, were the first to reach the Arctic Circle. These cold-adapted hunters apparently traversed Siberia and the Bering Straits at least 15,000 years ago (and new dates suggest humans may have been in the Americas as early as 18,500 years ago). But in 2004, researchers pushed that date further back in time when they discovered beads and stone and bone tools dated to as much as 35,000 years old at several sites in the Ural Mountains of far northeastern Europe and in northern Siberia; they also found the butchered carcasses of woolly mammoths, woolly rhinoceros, reindeer, and other animals. The Russian boy’s discovery—of the best-preserved mammoth found in a century—pushes back those dates by another 10,000 years. A team led by archaeologist Alexei Tikhonov excavated the mammoth and dubbed it “Zhenya,” for the child, Evgeniy Solinder, whose nickname was Zhenya. ^
“The big surprise, though, is the age. Radiocarbon dates on the collagen from the mammoth’s tibia bone, as well as from hair and muscle tissue, produce a direct date of 45,000 years, the team reports online today in Science. This fits with dating of the layer of sediments above the carcass, which suggest it was older than 40,000 years. If correct, this means the mammoth was alive during the heyday of woolly mammoths 42,000 to 44,000 years ago when they roamed the vast open grasslands of the northern steppe of the Siberian Arctic, Pitulko says. Researchers also have dated a thighbone of a modern human to 45,000 years at Ust-Ishim in Siberia, although that was found south of the Arctic at a latitude of 57° north, a bit north (and east) of Moscow. “The dating is compelling. It’s likely older than 40,000,” says Douglas Kennett, an environmental archaeologist who is co-director of the Pennsylvania State University, University Park’s accelerator mass spectrometry facility. However, he would like the Russian team to report the method used to rule out contamination of the bone collagen for dating—and confirmation of the dates on the bone by another lab, because the date is so critical for the significance of this discovery. ^
“Mammoths and other large animals, such as woolly rhinoceros and reindeer, may have been the magnet that drew humans to the Far North. “Mammoth hunting was an important part of survival strategy, not only in terms of food, but in terms of important raw materials—tusks, ivory that they desperately needed to manufacture hunting equipment,” Pitulko says. The presence of humans in the Arctic this early also suggests they had the adaptive ability to make tools, warm clothes, and temporary shelters that allowed them to live in the frigid north earlier than thought. They had to adapt to the cold to traverse Siberia and Beringia on their way to the Bering Strait’s land bridge, which they crossed to enter the Americas. “Surviving at those latitudes requires highly specialized technology and extreme cooperation,” Marean agrees. That implies that these were modern humans, rather than Neandertals or other early members of the human family. “If these hunters could survive in the Arctic Circle 45,000 years ago, they could have lived virtually anywhere on Earth,” says Ted Goebel, an archaeologist at Texas A&M University, College Station.” ^
The find also indicates that early Siberians were 4,660 kilometers (2,895 miles) from what was then a land bridge between modern Russia and Alaska. According to the Siberian Times: “A long distance, for sure, but far from insurmountable, opening the possibility that Stone Age Siberians colonised the Americas at this early point.” [Source: Anna Liesowska siberiantimes.com May 30, 2016]
Where Modern Humans Innate Explorers
“No other mammal moves around like we do,” says Pääbo told National Geographic.“We jump borders. We push into new territory even when we have resources where we are. Other animals don’t do this. Other humans either. Neanderthals were around hundreds of thousands of years, but they never spread around the world. In just 50,000 years we covered everything. There’s a kind of madness to it. Sailing out into the ocean, you have no idea what’s on the other side. And now we go to Mars. We never stop. Why?” [Source: David Dobbs, National Geographic, January 2013]
Elizabeth Kolbert wrote in The New Yorker: “From the archeological record, it’s inferred that Neanderthals evolved in Europe or western Asia and spread out from there, stopping when they reached water or some other significant obstacle. (During the ice ages, sea levels were a lot lower than they are now, so there was no English Channel to cross.) This is one of the most basic ways modern humans differ from Neanderthals and, in Pääbo’s view, also one of the most intriguing. By about forty-five thousand years ago, modern humans had already reached Australia, a journey that, even mid-ice age, meant crossing open water. Archaic humans like Homo erectus “spread like many other mammals in the Old World,” Pääbo told me. “They never came to Madagascar, never to Australia. Neither did Neanderthals. [Source: Elizabeth Kolbert, The New Yorker, August 15, 2011 ]
“It’s only fully modern humans who start this thing of venturing out on the ocean where you don’t see land. Part of that is technology, of course; you have to have ships to do it. But there is also, I like to think or say, some madness there. You know? How many people must have sailed out and vanished on the Pacific before you found Easter Island? I mean, it’s ridiculous. And why do you do that? Is it for the glory? For immortality? For curiosity? And now we go to Mars. We never stop.” If the defining characteristic of modern humans is this sort of Faustian restlessness, then, by Pääbo’s account, there must be some sort of Faustian gene. Several times, he told me that he thought it should be possible to identify the basis for this “madness” by comparing Neanderthal and human DNA.
““If we one day will know that some freak mutation made the human insanity and exploration thing possible, it will be amazing to think that it was this little inversion on this chromosome that made all this happen and changed the whole ecosystem of the planet and made us dominate everything,” he said at one point. At another, he said, “We are crazy in some way. What drives it? That I would really like to understand. That would be really, really cool to know.”“
David Dobbs wrote in National Geographic:: “If an urge to explore rises in us innately, perhaps its foundation lies within our genome. In fact there is a mutation that pops up frequently in such discussions: a variant of a gene called DRD4, which helps control dopamine, a chemical brain messenger important in learning and reward. Researchers have repeatedly tied the variant, known as DRD4-7R and carried by roughly 20 percent of all humans, to curiosity and restlessness. Dozens of human studies have found that 7R makes people more likely to take risks; explore new places, ideas, foods, relationships, drugs, or sexual opportunities; and generally embrace movement, change, and adventure. Studies in animals simulating 7R’s actions suggest it increases their taste for both movement and novelty. (Not incidentally, it is also closely associated with ADHD.) [Source: David Dobbs, National Geographic, January 2013 ]
“Most provocatively, several studies tie 7R to human migration. The first large genetic study to do so, led by Chuansheng Chen of the University of California, Irvine in 1999, found 7R more common in present-day migratory cultures than in settled ones. A larger, more statistically rigorous 2011 study supported this, finding that 7R, along with another variant named 2R, tends to be found more frequently than you would expect by chance in populations whose ancestors migrated longer distances after they moved out of Africa. Neither study necessarily means that the 7R form of the gene actually made those ancestors especially restless; you’d have to have been around back then to test that premise with certainty. But both studies support the idea that a nomadic lifestyle selects for the 7R variant.
“Another recent study backs this up. Among Ariaal tribesmen in Africa, those who carry 7R tend to be stronger and better fed than their non-7R peers if they live in nomadic tribes, possibly reflecting better fitness for a nomadic life and perhaps higher status as well. However, 7R carriers tend to be less well nourished if they live as settled villagers. The variant’s value, then, like that of many genes and traits, may depend on the surroundings. A restless person may thrive in a changeable environment but wither in a stable one; likewise with any genes that help produce the restlessness.
“So is 7R the explorer’s gene or adventure gene, as some call it? Yale University evolutionary and population geneticist Kenneth Kidd thinks that overstates its role. Kidd speaks with special authority here, as he was part of the team that discovered the 7R variant 20 years ago. Like other skeptics, he thinks that many of the studies linking 7R to exploratory traits suffer from mushy methods or math. He notes too that the pile of studies supporting 7R’s link with these traits is countered by another stack contradicting it. “You just can’t reduce something as complex as human exploration to a single gene,” he says, laughing. “Genetics doesn’t work that way.”
Image Sources: Wikimedia Commons except Africa sites, Science magazine, and Middle East migration routes, researchgate.com
Text Sources: National Geographic, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Nature, Scientific American. Live Science, Discover magazine, Discovery News, Natural History magazine, Archaeology magazine, The New Yorker, Time, BBC, The Guardian, Reuters, AP, AFP and various books and other publications.
Last updated September 2018