It seems quite certain now that all Europeans carry non-trivial ancient admixture from somewhere east of the Urals. We mostly share this genetic component with South Amerindians, but also with Siberians and East Asians. However, possibly because of its age, the precise levels of this influence across Europe are difficult to measure, and it's not yet clear who brought it to Europe and when.
The mystery deepened recently when it was shown by Kamberov et al. that Europeans lack a ~30,000-year-old, East Asian-derived variant of the EDAR gene which appears at high frequencies in all East Asian and Amerindian populations, and is also present in groups with well documented minor East Asian and Amerindian ancestry. For more background on that see this post at Gene Expression.
So something definitely doesn't add up. Perhaps the analyses showing Amerindian-like admixture in Europeans are flawed? Or maybe this EDAR mutation is actually much younger than 30,000 YBP, and the eastern groups that apparently migrated to Europe came at a time when it didn't exist or was still very rare?
Then again, maybe Europeans don't carry this mutation because by and large we don't have East Asian admixture? In other words, perhaps the mysterious eastern component shared by Europeans, Amerindians and East Asians came from a now extinct population in Siberia? If so, this component might have been picked up by the (East Asian EDAR carrying) ancestors of Amerindians as they moved into the Americas. In fact, perhaps whoever carried this component blocked the entry of any (East Asian EDAR carrying) East Eurasians proper into Europe at a critical time when population densities in West Eurasia were very low?
So the other thing I'm getting at is that Amerindians and East Asians might be ancient hybrid groups, just like Europeans and South Asians. Indeed, David Reich has made some comments to that effect, and it seems we might soon see a paper on the topic.
In any case, what is certain is that we're still in for some major surprises when it comes to our deep genetic ancestry. That's because no matter how many statistically sound studies come out showing signals of various types of prehistoric admixture in Europeans and others, only ancient DNA from C14 dated remains can ultimately verify and explain such results.
References...
Gene Expression: Is Girls’ Generation the outcome of the Pleistocene mind?
Yana G. Kamberov et al., Modeling Recent Human Evolution in Mice by Expression of a Selected EDAR Variant, Cell, Volume 152, Issue 4, 691-702, 14 February 2013, 10.1016/j.cell.2013.01.016
See also...
Europeans are a three-way mix, with a whopping 20-40% ancient North Asian ancestry
ADMIXTURE and STRUCTURE tests aren’t formal mixture tests
As I believe I commented before (if not in this blog somewhere else), I suspect that the Native American arrow is pointing in the wrong direction and that that issue and others are indications of the high rate of fallibility of the "Mix" algorithms, which need a lot of polishing at the very least and cannot be considered more than a "beta" or maybe even an "alpha" stage in spite of the enthusiasm of some about them.
ReplyDeleteHowever there is another issue: there are many genetic indicators (Y-DNA, mtDNA and autosomal DNA as measured with STRUCTURE/ADMIXTURE) telling of low-level (but still significant) admixture in NE Europeans of Uralic ancestry, including North Russians. However the North Russian pie chart in this paper also lacks the East Asian variant of EDAR, meaning that either it is low in West Siberian Natives (not shown in the map, as are not shown European Uralic peoples) or that some sort of phenotype ("racist") selection against it took place in the Far North of Europe.
I think this ancient admixture is something Central Siberian or Central Asian, and it's shared by Europeans, Amerindians and East Asians. It might well be the same thing as what the proto-Uralics were before they mixed with Europeans and East Asian EDAR carrying eastern Siberians.
ReplyDeleteI believe it was selected against also. The average cup-size of Eastern European women is among the highest in the world, if not the highest. I mean looking at the map, EDAR appears abent in many SE Asian populations as well but this doesn't mean there hasn't been contact/admixture with populations with the EDAR gene.
ReplyDeleteThe map I posted above shows an absence of this mutation in Papuans, who don't have East Asian admixture, but it's found in all the other Southeast Asian samples, including Oceanians with East Asian admixture.
DeleteAh, yeah I see now. Sorry, I was looking at the display on the right.
DeleteConsider the following. The recent origin of Amerindians from Siberia is unlikely (Amerindians don't have blood group B, Y-DNA N and O, but they have mtDNA X and B, which are rare to non-existent in Siberia). At the same time, a connection with Europe to the exclusion of East Asia is something that we observe across multiple genetic systems (autosomal "Amerindian" component, mtDNA hg X, hg B - sister haplogroup to West Eurasian hg U, mtDNA hg C1, Y-DNA hg Q and R). EDAR achieves its highest frequencies in the Americas, so that's probably where it originated. Amerindians also have the ancestral EDAR allele. So, a polymorphic EDAR +/- Amerindian population split into an East Asian EDAR+ branch and a European EDAR- carrying branch. We may find some derived EDAR alleles in ancient European remains just like we find shovel-shaped incisors (most frequent in Amerindians and East Asians and rooted in the same EDAR gene) in Gravettian, Catalhoyuk and other Paleolithic and Neolithic remains in Western Eurasia.
ReplyDelete