This Wall et al. paper is the third study in a row on Neanderthal ancestry in modern humans in which East Asians clearly top the list as the most Neanderthal-admixed group. The reasons for this aren't yet clear. The study also picked up low level Neanderthal influence in the Maasai of Kenya, which was most likely the result of significant and relatively recent admixture from Eurasia into these Africans (estimated at around 30% in each Maasai genome).
By using the high coverage Denisova genome, we are able to show that the admixture rate into East Asians is 40% higher than into Europeans. We conclude that admixture between Neanderthals and modern humans did not occur at a single time and place, as suggested by GREEN et al. (2010). Some of it had to have occurred after the separation of East Asians and Europeans. Further, we show that there was significant Neanderthal admixture into the Maasai population of East Africa, probably because of secondary contact with a non-African population rather than admixture directly from Neanderthals.
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Our new method for identifying introgressed Neanderthal fragments in human populations detected 226 different putative Neanderthal regions. The relative frequencies of these putative Neanderthal haplotypes in the 42 sampled modern human individuals then provide estimates of the relative contributions of Neanderthal DNA to the gene pools of contemporary human populations. We found that on average the ‘Neanderthal haplotypes’ were at higher frequency in the East Asians than in the Europeans (9.6% vs. 6.4%; p = 3.0 x 10-4, permutation test), consistent with the D-statistic results presented in Figure 3. We also found evidence for a small, but statistically significant, Neanderthal contribution to the genomes of the Maasai (p = 4.9 * 10-4), but did not find a significant difference in Neanderthal haplotype frequency between the East and South Asian samples (p >0.05).
Jeffrey D. Wall et al., Higher levels of Neanderthal ancestry in East Asians than in Europeans, Genetics: Early Online, published on February 14, 2013 as 10.1534/genetics.112.148213
See also...
Oetzi more Neandertal than modern Europeans because his ancestors came from...North Africa?
I can't see anywhere that figure of 40% at the D-stats: Europeans mark c. 0.65 and East Asians c. 0.75 (fig. S1, fig. S3), what, if my maths are correct, makes East Asian only 15% more Neanderthal than Europeans on average.
ReplyDeleteAlso, as I see it, that can well be explained by either of the following factors (or both): (a) founder effect among East Asians (known to have rather low genetic diversity) or (b) African admixture among Europeans. In favor of the latter weights that Tuscans (slightly more African than Northern Europeans, all at low levels, of course) show somewhat less Neanderthal input than CEU (about 0.5 points in the D-stats, equivalent to 8% more Neanderthal admixture among CEU relative to TSI). Against however weights that GIH (apparently unmixed with Africans at all) have similar (but slightly higher) figures to CEU.
So IMO what weights the most is an East Asian founder effect but low-level African admixture in Europeans also weights somewhat at South+West Eurasian levels.
The study says 40% on two separate occasions so it's unlikely to be a typo. But it might be.
DeleteI don't think it's a typo but I fail to see the evidence. I hoped you could point me to that "blind spot".
DeleteFrom a quick look just now I have no idea how they got 40%, but I'll have another look later today when I finish my next blog entry.
DeleteErratum: should be "fig. 3 and fig. S1" instead of "fig. S1 and fig. S3", sorry.
ReplyDeleteSome of you are mentioning that you fail to see the evidence behind this finding. Well, you do realize that this is just a blog mentioning what a study found, right? This is not the original source of the material being discussed.
ReplyDeleteUnless you subscribed to the site, or the article itself, not sure how genetics.org does it's business, then how could you see much of anything? If you are only basing your opinion on what is mentioned in this blog article, then, and I'm sugar coating it here, you are jumping to conclusions. However, even if you clicked the link to the abstract at the top of the article, you are not seeing enough of the picture to formulate that kind of opinion, to say the least. An abstract is a formal but brief outline designed to give the reader a general understanding of the purpose of the data collected in an observational study or experiment and the conclusions deduced as well as any hypothesis that might have been formed as a result of the study and any theories the study might pertain to, or an experimental hypothesis, the relevant experimental methods and data, conclusions, and any theories that the hypothesis might pertain to in a scientific experiment. However, in any case, there will be few details given in an abstract. That is not the purpose of the abstract. By the time the reader finishes reading an abstract, he or she will normally know whether or not they need to continue with the full report for their purposes.
Spanky: the article is freely available, at least I have no problem accessing it right now. You got me a bit cold (several months after I commented first) but I'm pretty sure that I was talking based on the paper and supporting information and not just on what Davidski wrote here nor the abstract.
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