Many mysteries about human origins will be solved thanks to the advent of full genome sequencing. Hammer et al. found archaic admixture in Africans on just 61 genomic regions, each about ~20kb in length.From LiveScience via Razib:
I'm willing to bet that once scientists turn their attentions to full genomes, they will have substantial and indisputable evidence for genetic divergence between stretches of human DNA that simply too deep to be explained in a conventional Out-of-Africa timeframe.
If there was substantial archaic admixture in Africa c. 35ka, according to Hammer et al.'s estimate, and coinciding with the (intrusive?) appearance of Upper Paleolithic modern humans such as Hofmeyr, then full genome sequencing will provide the smoking gun evidence for it. Such an event would simultaneously solve many mysteries about the African population, such as its apparent higher effective population size, greater allele diversity, and recombination rate.
Our species might have also hybridized with a now-extinct lineage of humanity before leaving Africa, according to findings this year from Hammer and his colleagues. Approximately 2 percent of contemporary African DNA might have come from a lineage that first diverged from the ancestors of modern humans about 700,000 years ago. For context, the Neanderthal lineage diverged from ours within the past 500,000 years, while the first signs of anatomically modern human features emerged only about 200,000 years ago.
Hammer noted that he and his colleagues were very conservative with their analysis, only looking for lineages that diverged even more from modern humans than Neanderthals. "It's possible there may be others we can detect that are more closely related to modern humans," Hammer told LiveScience.
"We've probably just scratched the surface of what we might find," Hammer added. "We only looked at a small number of regions of the genome. This coming year, you'll see a lot of progress made with full genome data. This year, we should be able to confirm what we found and go way beyond that."I started talking about "Afrasians" mixing it up with "Palaeoafricans" as a major cause for African genetic diversity back in 2005. From a 2006 treatment:
It is clear that the small early modern human population must have inhabited a correspondingly small geographical region, so it is not surprising that in their movements within Africa they would have interbred with the pre-existing humans. After all, humans lived in Africa for a long time before the emergence of the moderns, and there is no reason to believe that all the African branches of humanity were wiped out to be replaced by the advancing moderns.
I predict that in the coming years, we will learn much more about the different strata of genetic ancestry contained in Africans, as well as Europeans and East Asians. Note, also, that there is no candidate for the source population of the archaic contribution of West Africans. This, again, is not surprising, because western Africa has a much less advantageous climate than eastern Africa for bone preservation, in addition to being less well researched. Even in Europe, where anthropological science is the oldest, and cave surveys have been numerous, there are still only a handful of well-preserved Neanderthal specimens. Hopefully, some of the archaics of Africa remain to be discovered.Some of these archaics have indeed been found.
All indications point in the direction that the Afrasian/Palaeoafrican theory is about to be confirmed. I purposefully decided to name the major recent component in our species' ancestry "Afrasian", because I did not want to take a strong stand on where this component originated (Africa or Asia). My reticence to jump on the recent Out-of-Africa bandwagon with both feet, seems to have been well-justified, as Out-of-Arabia seems to be an increasingly strong possibility: from the LiveScience piece, once again:
"I hope that our findings will stimulate research in South Asia — India in particular — to find the remains of early anatomically modern humans in that part of the world,"archaeologist Hans-Peter Uerpmann from Eberhard Karls University in Tubingen, Germany, told LiveScience.
"Our focus this year will be on gathering evidence to reconstruct the paleoclimate in southern Arabia during the ice age that lasted between 75,000 and 60,000 years ago," paleolithic archaeologist Jeffrey Rose at the University of Birmingham in England told LiveScience. This will help researchers determine how friendly or hostile the climate was back then "to help understand the fate of these early humans on the Arabian Peninsula."
If these ancient peoples eventually died off in Arabia, they would just be a failed migration out of Africa. However, if they survived, they may be the ancestors "to all non-African people living on Earth," Rose said. "Only further exploration throughout Arabia will answer these questions."These Middle Stone Age inhabitants of Arabia may not just be the ancestors only of everyone outside Africa, but of many within Africa itself.
"If these ancient peoples eventually died off in Arabia, they would just be a failed migration out of Africa".
ReplyDeleteNot necessarily so. They could well have died off in Arabia but, by that time, have moved far beyond that region.
"These Middle Stone Age inhabitants of Arabia may not just be the ancestors only of everyone outside Africa, but of many within Africa itself".
I agree. I am fairly sure the distribution of Y-DNA indicates E originated outside Africa. All its 'relations' are outside that continent. And several M and N haplogroups also look very likely to have moved into Africa. I'm yet to be convinced of your theory that L3 originated outside Africa though.
Here my proposal:
ReplyDeleteFirst ancient modern humans originate in South Africa, like the genetics of the San people and the Blombos cave suggests. They were relatively pacific tribes, hunting, gathering and using coastal resources. This will explain why non-L3 hunter gatherers today do not train as warriors nor practice ritual fights (Moreno, 2011).
Second, they spread along the eastern african coast towards the red sea, between africa and arabia, where L3 arises. The shape of the red sea, with its richness in seafood, provokes population growth along the coast on both sides of the red sea.
Among the L3 haplotype a tribe of incipient warriors appears, probably as a cause of the increased population density, and this tribe of incipient warriors (M,N) spreads inside and outside of africa. This will explain why non-african hunter gatherers practice ritual fights and most of them train as warriors (Moreno, 2010,2011).
I believe the causes for most of the present day diversity in Human DNA, were the practices of deliberate inter-species hybridization among ancient agriculturalists. Most of the so-called archaic hominids, such as Neanderthal, Erectus, Denisovans, etc., were unnatural & biologically unsuccessful hybrids ~created by Homo Sapiens. That's why genetic remnants of various types of lower apes are found in many 'modern' Humans. Evidence of inter-species hybridization is found in a variety of distinctive types, which were historically concentrated continentally among some indigenous tribes; but now that Earth has become so populated, & with the aid of technology (transportation especially), we now have even more varied combinations of different genes within specific individuals and/or ethnic groups. Blood types, factors, & groups, give us some clues about the origins & chronologies of some of the most identifiable hybrids. In other words, I believe that humans were deliberately bred (by humans, not by aliens, lol) with various lower apes or Rhesus macaque monkeys, mostly in the regions where those animals are native, & at various times throughout the eras of very early agricultural development. Breeding and hybridization is/was of prime importance to agriculturalists, & often a great source of delight, pride, & satisfaction, to people experimenting with them.
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