tag:blogger.com,1999:blog-7785493.post4455852523905779676..comments2024-01-04T04:11:55.717+02:00Comments on Dienekes’ Anthropology Blog: Archaic introgression in PygmiesDienekeshttp://www.blogger.com/profile/02082684850093948970noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-7785493.post-25173052439556393492016-02-22T03:50:28.703+02:002016-02-22T03:50:28.703+02:00A question for you better educated on this topic. ...A question for you better educated on this topic. I have seen estimates that pygmies diverged over 100,000 years ago from other modern African populations. But couldn't that early date be an artifact of this proposed archaic admixture? If any significant amount of 'other' genes entered the pygmy population relatively recently, wouldn't show up as if they had diverged far earlier than they really did? Tom Bridgelandhttps://www.blogger.com/profile/13098048586042365606noreply@blogger.comtag:blogger.com,1999:blog-7785493.post-1699182833465557762016-02-21T21:47:47.778+02:002016-02-21T21:47:47.778+02:00This comment has been removed by the author.Fiend of 9 worldshttps://www.blogger.com/profile/17712083368615685458noreply@blogger.comtag:blogger.com,1999:blog-7785493.post-31909524784445825052016-02-21T21:42:25.968+02:002016-02-21T21:42:25.968+02:00This comment has been removed by the author.Fiend of 9 worldshttps://www.blogger.com/profile/17712083368615685458noreply@blogger.comtag:blogger.com,1999:blog-7785493.post-57632463436935211272016-02-19T22:57:40.020+02:002016-02-19T22:57:40.020+02:00"I have little doubt that most if not all of ..."I have little doubt that most if not all of the supposedly "old divergences" between African populations are a mirage created by admixture between modern humans and archaic "Palaeoafricans."<br /><br />This doesn't ring true. Y-DNA A and B which are almost exclusively African are more basal, than the Y-DNA CF clade, which makes up the lion's share of non-African Y-DNA. mtDNA L0, L1 and L2 which are almost exclusively African are more basal than Y-DNA M and N which makes up virtually all non-African mtDNA. The peak level of admixture from any single species is small, and except for Neanderthals limited to relict first contact populations. The other reported statistical evidence of archaic admixture also involves a small percentage in an isolated Paleo-African population.<br /><br />The bottleneck in mtDNA between the effective size of M and N v. the effective size of L3 (including M and N) as a whole, corroborates the fact that non-Africans should be less genetically diverse than Africans due to this founder effect. There is no archaeological trace of AMHs outside Africa prior to 125kya. The earliest genetic trace of AMH-Archaic hominin admixture from Altai Neanderthal DNA is 100kya, but there's evidence of modern humans in Africa back to 200kya and Africa is clearly where AMHs evolved. Ancient admixture is too small a factor to substantially distort this basic narrative.<br /><br />African diversity may be elevated by Eurasian back migration to Europe that gives Africa a sliver of Eurasian diversity in addition to pre-existing African diversity. But, there is every reason to think that Africa is more genetically diverse to start with.<br /><br />"A handful or two of archaic genomes from Eurasia needs an ever-more-complex web of admixtures to make sense of; Africa will need no less, and -if morphological variability persistence is any criterion- a lot more."<br /><br />I think that we are very near the end of the road with Eurasian archaic admixture. I'd be very surprised to see more than one additional source of non-African admixture and any such admixture would have to be in a pretty small subset of genetically sampled populations, less than 1% ancestry, and/or from a population that has been population genetically isolated for a long time and not yet been genetically sampled (e.g. some population in an isolated valley in some Chinese mountain range that has been virtually untouched). Any other archaic sources are not just practically, but theoretically impossible to discover.<br /><br />We have one confirmed but not described archaic source in African pygmies within the last 30kya. Previous studies have pointed to at least one more. If we could find more ancient African DNA, I agree that we might be able to find some additional ancient admixture that is older, and that perhaps 1-2 such additional finds might actually happen. (Note that the ancient DNA need not itself be archaic. It would suffice to find ancient AMH DNA that predates the additional archaic hominin admixture event or better yet, ancient AMH DNA immediately before and not long after the additional archaic hominin admixture event). But the window for that to happen is pretty much in parts of Africa that were inhabited by AMHs during the time frame of 40kya to 250kya and even then, we are talking about 3-4 archaic admixture events in all of African history, at least two of which are confined to small Paleo-African populations. Thus, the "Ewok village" of human origins won't get a lot more complex than it already is, and any new tweaks will be smaller in magnitude than what we have already discoveredandrewhttps://www.blogger.com/profile/08172964121659914379noreply@blogger.comtag:blogger.com,1999:blog-7785493.post-67225617453348137172016-02-19T10:33:00.911+02:002016-02-19T10:33:00.911+02:00I am trying to teach a course on human variation a...I am trying to teach a course on human variation and adaptation at the moment, and I feel like the flow of archaic introgression and function papers has turned into a flood over the last six months. Trying to keep my lecture notes up to date is a nightmare - we only yesterday discussed the pygmy phenotype!Athenahttps://www.blogger.com/profile/07792495610209362494noreply@blogger.com