Recent African origin of modern humans

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Schematic representation of one theory of divergence and interbreeding of different groups. The horizontal axis shows geographic location; the vertical axis shows time in millions of years ago. Blue areas show presence at a given time and place. Early modern humans are shown spreading from Africa across the globe, but also interbreding at different places with other descendants of Homo heidelbergensis, namely Neanderthals, Denisovans, and unknown archaic African hominins (top right).[1]
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The recent African origin of modern humans theory argues that a recent group originating in Africa spread to the rest of the world and replaced archaic human groups, such as the Neanderthals. It is typically contrasted with the multiregional origin of modern humans theory, according to which the modern humans originated from several different archaic human groups who lived in different regions.

Political correctness

The recent African origin of modern humans is a more politically correct theory than the multiregional theory, since it argues for a more "uniform" current humanity and thus race denialism. Other politically correct aspects include that this occurred relatively recently and only occurred once, again supporting a "uniform" humanity.

Giving prominence to Africa over other regions may also be seen as politically correct.

Likely partly because of this, the theory has been very popular among Western anthropologists and in Boasian anthropology.

This may also be an explanation for why disproportionate money and fieldwork have been spent on Africa compared to other regions, in turn possibly causing bias regarding findings.[2]

Enough time for the development of different human races?

One politically correct reason for arguing for "young" modern humans is that this is argued to mean that there has not been enough time for the development of different human races. However, as stated below in this article, various findings support much older ancestries than previously assumed.

Furthermore, even short time periods can cause great genetic changes, which has been argued to be the case for humans, such as after the development of agriculture. See Arguments regarding the existence of races: Enough time?

Older African origin of archaic human groups theories

Multiregional theories have often argued for a common African origin for the different archaic human groups, but one which is much older than that proposed in the recent African origin theories.

Thus, the expression "Out of Africa" is ambiguous, since it can refer to different argued emigrations by different human groups from Africa.

There are also theories that dispute that archaic human groups such as Homo erectus originated in Africa.

Recent findings

Origins and dispersals of anatomically modern humans

A 2017 study stated support for that the earliest divergence between different populations of anatomically modern humans in Africa occurred 350,000 to 260,000 years ago, much earlier than previous estimates.[3]

Evidence presented in 2017 was argued to support that "the extreme age of the bones makes them the oldest known specimens of modern humans and poses a major challenge to the idea that the earliest members of our species evolved in a “Garden of Eden” in East Africa one hundred thousand years later. “This gives us a completely different picture of the evolution of our species. It goes much further back in time, but also the very process of evolution is different to what we thought,” Hublin told the Guardian. “It looks like our species was already present probably all over Africa by 300,000 years ago. If there was a Garden of Eden, it might have been the size of the continent.”"[4]

Recent evidence has been argued to support that anatomically modern humans dispersed in more than one wave of migration out of Africa.[5]

One aspect of the politically correct view has been that humans from Africa began colonizing the world only around 50,000-60,000 years go. However, recent findings have been stated to support the presence of anatomically modern humans in China around 100,000 years ago. "It is also not clear why modern humans would have reached East Asia so long before they reached Europe, where the earliest remains are about 45,000 years old. Martinón-Torres suggests that humans could not gain a foothold in Europe until Neanderthals there were teetering on extinction. The frigid climate of Ice Age Europe may have erected another barrier to people adapted to Africa, says Petraglia."[6]

Evidence presented in 2017 was argued to support that "important characteristics of humans actually developed in east Asia [...] there might have been times of intense intermingling as those early humans in Asia moved out of and back into Africa, with no single event when modern humans came into being. That means that modern humans are made up of the DNA of ancestors from both Asia and Africa, if the researchers are correct."[7]

Interbreeding with archaic humans

Recent genetic evidence has proven some level of interbreeding of anatomically modern humans with Neanderthals, Denisovans, archaic groups in Africa, and possibly other archaic groups, and so in its most strict and politically correct form, the recent African origin of modern humans theory has been discredited.[8][9][10] This makes the ancestry and genetics of different human groups much more complicated, heterogeneous, and older than previously thought.

A 2017 study found that a higher degree of Neanderthal-originating genetics in modern humans is associated with having a skull shape having a higher degree similarity with Neanderthal skull shape. Furthermore, this was associated with the shape of different brain regions and the study suggested that "Neanderthal-derived genetic variation is neurologically functional in the contemporary population."[11]

The multiregional theory has been popular in East Asia, since the recent African origin theory is argued to be unable to explain phenomena such as similarities between East Asian Homo erectus and modern East Asians. A 2016 article in Nature stated that most Chinese palaeontologists think that "hominins descended from H. erectus in Asia interbred with incoming groups from Africa and other parts of Eurasia, and their progeny gave rise to the ancestors of modern east Asians".[12] This would make the ancestry and genetics of different human groups even more complicated, heterogeneous, and older.

Other recent findings

Evidence in 2017 was stated to support the presence of (archaic) humans in the Americas 130,000 years ago, over 100,000 years earlier than previously thought.[13] There are also other recent controversial findings and theories on early settlers of the Americas, as discussed in the Amerindians article.

In 2018, "Archaeologists in Algeria have discovered stone tools and cut animal bones that may be up to 2.4 million years old, bringing into question East Africa’s title as the cradle of humanity [...] East Africa is widely considered to be the birthplace of stone tool use by our ancient hominid ancestors — the earliest examples of which date as far back as about 2.6 million years ago [...] the findings suggest that the ancestors of modern people were present in north Africa at least 600,000 years earlier than scientists thought. [...] suggest that hominin fossils and Oldowan artifacts as old as those documented in East Africa could be discovered in North Africa as well.''[14]

Evidence presented in 2017 was argued to support that the split between the groups that developed into chimpanzees and humans occurred in Europe rather than in Africa.[15]

Claimed origin of "Behavioral modernity" in Africa

"Behavioral modernity" is an argued set of behavioral and cognitive traits that distinguish recent humans from other groups. There is a debate regarding the relationship between (relatively) anatomically modern humans and behavioral modernity, with older anatomically modern humans groups not necessarily displaying behavioral modernity, based on archeological evidence.

There have been political correct claims that behavioral modernity originated in Africa. "The evidence for significant cultural advancements in Europe earlier than anywhere else in the world is largely ignored by scholars and the public alike, because it does not fit the politically-motivated idea that humanity was an African invention and that the human brain was born there, after which it has remained fixed and resistant to all effects of evolution. If cultural modernity first arose in Europe, after anatomically modern humans spread out of Africa, then the possibility arises that populations who remained in Africa may have been left behind on the brain train. Obviously, this won’t do in a discipline steeped in Boasian cultural relativism.

Over the past few years, the concept of behavioral modernity has become rather unfashionable within the inner-circle of prehistorian scholars. It is probably no coincidence that this concept lost steam after the political implications of behavioral modernity arising in Europe first were realized [...] Frankly, the concept of behavioral modernity was always dubious, and arguably only ever gained popularity as a political tool for the “we’re all the same under the hood” crowd. It was claimed that behavioral modernity was the tipping point when culture took over natural selection and the human brain was locked into its current state. [...] Advancements in human genomic studies have shown that such a concept is manifestly untrue. To believe that the modern human brain has somehow been magically spared from the effects of natural selection is no less an act of faith than to believe that the world was created on October 23, 4004 B.C."[16]

See also

External links


Anatole Klyosov

References

  1. Stringer, C. (2012). "What makes a modern human". Nature 485 (7396): 33–35. doi:10.1038/485033a. PMID 22552077 https://www.ncbi.nlm.nih.gov/pubmed/22552077
  2. Oldest Tools Outside Africa Found, Rewriting Human Story https://www.amren.com/news/2018/07/oldest-tools-outside-africa-found-rewriting-human-story/
  3. Southern African ancient genomes estimate modern human divergence to 350,000 to 260,000 years ago http://science.sciencemag.org/content/358/6363/652
  4. Oldest Homo sapiens bones ever found shake foundations of the human story https://www.theguardian.com/science/2017/jun/07/oldest-homo-sapiens-bones-ever-found-shake-foundations-of-the-human-story
  5. Humans May Have Dispersed Out of Africa Earlier Than Thought https://www.amren.com/news/2014/04/humans-may-have-dispersed-out-of-africa-earlier-than-thought/
  6. Teeth from China reveal early human trek out of Africa https://www.nature.com/news/teeth-from-china-reveal-early-human-trek-out-of-africa-1.18566
  7. Skull found in China could re-write 'out of Africa' theory of human evolution https://www.independent.co.uk/news/science/evolution-theory-out-of-africa-dali-skull-china-homo-erectus-sapiens-latest-a8064306.html
  8. Alves I, Šrámková Hanulová A, Foll M, Excoffier L (2012) Genomic Data Reveal a Complex Making of Humans. PLoS Genet 8(7): e1002837. doi:10.1371/journal.pgen.1002837 http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1002837
  9. Hammer, M.F.; Woerner, A.E.; Mendez, F.L.; Watkins, J.C.; Wall, J.D. (2011). "Genetic evidence for archaic admixture in Africa". Proceedings of the National Academy of Sciences 108 (37): 15123–15128. doi:10.1073/pnas.1109300108 http://www.pnas.org/content/108/37/15123.full
  10. Evolutionary History and Adaptation from High-Coverage Whole-Genome Sequences of Diverse African Hunter-Gatherers. Joseph Lachance, Benjamin Vernot, Clara C. Elbers, Bart Ferwerda, Alain Froment, Jean-Marie Bodo, Godfrey Lema, Wenqing Fu, Thomas B. Nyambo, Timothy R. Rebbeck, Kun Zhang, Joshua M. Akey, Sarah A. Tishkoff. Cell - 3 August 2012 (Vol. 150, Issue 3, pp. 457-469) http://www.cell.com/abstract/S0092-8674%2812%2900831-8
  11. Neanderthal-Derived Genetic Variation Shapes Modern Human Cranium and Brain https://www.nature.com/articles/s41598-017-06587-0
  12. How China is rewriting the book on human origins http://www.nature.com/news/how-china-is-rewriting-the-book-on-human-origins-1.20231
  13. Controversial study claims humans reached Americas 100,000 years earlier than thought https://www.nature.com/news/controversial-study-claims-humans-reached-americas-100-000-years-earlier-than-thought-1.21886
  14. 2.4-Million-Year-Old Tools Found in Algeria Could Upend Human Origin Story https://www.telegraph.co.uk/news/2018/11/30/24-million-year-old-tools-found-algeria-could-upend-human-origin/
  15. Fuss J, Spassov N, Begun DR, Böhme M (2017) Potential hominin affinities of Graecopithecus from the Late Miocene of Europe. PLoS ONE 12(5): e0177127. https://doi.org/10.1371/journal.pone.0177127 http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0177127
  16. Anthropology’s Obsession with African Origins https://www.theoccidentalobserver.net/2017/07/28/anthropologys-obsession-with-african-origins/