October 29, 2013

Intra-African variation in Neandertal admixture is due to non-African admixture

I haven't read this, but the idea seems to be that variation between Africans in Neandertal admixture can be wholly explained by recent admixture with Eurasians (who already had this type of admixture). This is not very surprising, given that Neandertals were a Eurasian-distributed species, so that admixture with them cannot have taken place in Africa.

The finding that Africans don't vary in their Neandertal admixture suggests that the source cannot have been an unknown African hominin related of Neandertals (in which case we'd expect to see variation in Africans). I don't know of any anthropologically plausible African cousin of the Neandertals, but, of course, the lack of anthropological evidence does not mean non-existence (cf. Denisovans as an anthropologically invisible Neandertal relative in Eurasia).

Genome Biol Evol. 2013 Oct 25. [Epub ahead of print]

Apparent Variation in Neanderthal Admixture among African Populations is Consistent with Gene Flow from non-African Populations.

Wang S, Lachance J, Tishkoff S, Hey J, Xing J.

Abstract

Recent studies have found evidence of introgression from Neanderthals into modern humans outside of sub-Saharan Africa. Given the geographic range of Neanderthals, the findings have been interpreted as evidence of gene exchange between Neanderthals and the modern humans descended from the Out-of-Africa (OOA) migration. Here we examine an alternative interpretation in which the introgression occurred earlier within Africa, between ancestors or relatives of Neanderthals and a subset of African modern humans who were the ancestors of those involved in the OOA migration. Under the alternative model, if the population structure among present-day Africans predates the OOA migration, we might find some African populations show a signal of Neanderthal introgression while others do not. To test this alternative model we compiled a whole-genome data set including 38 sub-Saharan Africans from eight populations and 25 non-African individuals from five populations. We assessed differences in the amount of Neanderthal-like SNP alleles among these populations and observed up to 1.5% difference in the number of Neanderthal-like alleles among African populations. Further analyses suggest that these differences are likely due to recent non-African admixture in these populations. After accounting for recent non-African admixture, our results do not support the alternative model of older (e.g., >100 kya) admixture between modern human and Neanderthal-like hominid within Africa.

Link

4 comments:

barakobama said...

Is there evidence in autosomal DNA they have any West Eurasian(European, Near eastern, north African) ancestry or any other type of non African ancestry. I know that east Africans have a lot of southwest Asian ancestry their high amount of Y DNA J1, southwest Asian in globe13 and K12b, and sometimes Caucasian skull shapes.

What is a Neanderthal is there real proof it was s species or many related breeds. If we had a Densovian skull would it be classified as a Neanderthal. So many Neanderthal skulls are so different way different skulls of humans around the world today. So I don't think it is smart to generalize Neanderthals from the few DNA samples of Neanderthals there are.

Onur said...

Is there evidence in autosomal DNA they have any West Eurasian(European, Near eastern, north African) ancestry or any other type of non African ancestry.

The full paper is available here:

http://gbe.oxfordjournals.org/content/early/2013/10/25/gbe.evt160.full.pdf+html

See the result of the ADMIXTURE analysis in Figure 3 at the end of the paper. There you will see that the said Negroid groups are indeed clearly non-Negroid-admixed (probably ultimately from Eurasia in all of them).

eurologist said...

What is a Neanderthal is there real proof it was s species or many related breeds. If we had a Densovian skull would it be classified as a Neanderthal. So many Neanderthal skulls are so different way different skulls of humans around the world today.

barakobama,

Not really. Most of the differences between Neanderthal skull morphology are well documented in time and space: Iberia seems to show the first transition towards Neanderthal features, followed by ~Central Europe around 300,000 - 150,000 ya, with the E, SE, the Levant, and West Asia lagging until around 60,000 ya (and even then there was a W-E cline in features that distinguish Neanderthal from heidelbergensis).

Both mt-DNA and autosomal DNA show low population numbers and at least three (but likely four, when anatomy is included) subgroups (SW, W and N Europe; SC/ SE Europe; extreme E Europe and NW Asia; the Levant [and perhaps Iran etc.]).

Yet, all of these are clearly Neanderthal - anatomically, from their mt-DNA branches, and autosomically.

In addition, there were likely groups farther east related to the original heidelbergensis, and to E Asian erectus. Denisova may have been a hybrid of sorts between any of these - it will take more ancient DNA samples to clarify.

All of them likely could successfully interbreed with each other and with AMHs - so one has to be careful with the "species" nomenclature.

mikej2 said...

Wondering the Finnish result I made a simple statistics based on the distribution list of Eupedia, pointing out what is the common proportion of all yDna haplotypes between neighbouring countries and Maris, who seem to be the least mixed FU-people there. These are percetages for Finns:

Maris 62
Estonia 58,5
Lithuania 57,5
Latvia 53,5
Sweden 44,5
Norway 40
Denmark 38,5

To make a comparison, I took Latvians and made the same

Lithuania 90,5
Maris 85
Estonia 83,5
Finland 53,5
Norway 48,5
Sweden 44,5
Denmark 37,5