Saturday, February 21, 2015

Basal Eurasian in Kostenki14

This one's a strange find from last year that was recently followed up on by Haak et al. 2015, it's the idea that Kostenki14, an ancient (~36,000-38,000 BP) West Eurasian (Russia) Upper Paleolithic individual actually shows the Qausi-African Basal Eurasian component

This is quite strange in that for now this has only been found in Early European Farmers who were more or less Neolithic West Asians with a certain degree of Western European Hunter-Gatherer (native European component) ancestry (~30% or less).

When the findings in Seguin-Orlando et al. 2014 to which we owe that diagram above first came out, David Reich who had a key part in Lazaridis et al. as well as Haak et al. went so far as to suggest that Kostenki14's sample was contaminated & that these results perhaps couldn't be relied upon (last paragraph). 

Haak et al. which he had an important role in finally decided to incorporate Kostenki14 and the subject of his Basal Eurasian admixture into their study and for example share the following points:

"The hypothesis of Basal Eurasian ancestry in Kostenki14 needs to be further tested, as the negative D(Mbuti, Han; Loschbour, Kostenki14) statistic could also reflect gene flow between Han<->Loschbour a priori plausible, as these populations are much younger than Kostenki14 and may share intra-Eurasian genetic drift that Kostenki14 lacks because of its age. The possibility of later gene flow between Europeans and eastern non-Africans must be further tested with additional ancient samples from Upper Paleolithic Europe and Asia."

Frankly they're skeptical and even went so far as to suggest that this isn't the same affinity we find in Early European Farmers with ancestors from the Near East; claiming that this in some models even looks like a lineage that split before the split of the Basal Eurasian in West Asians & Early European Farmers from West Asia:

Other models include Kostenki14 sharing in the Basal Eurasian that was in the Early Farmers & many European & West Asian populations today which I frankly find unlikely however they note that no model making Kostenki14 out to be a single branch off fits; as in Kostenk14 can't fit as a simple break off from "West Eurasian Upper Paleolithic" or anything of the sort, instead a 2-way branch for the time being (like Basal Eurasian + WEUP) makes more sense.

Ultimately the study leaves you with honestly not many answers at the very end, we need more data, ancient genomes from East Eurasians might be able to explain this, this could be Kostenki14 being the extremely old individual he is showing affinities for populations whose divergence he long precedes etc etc. And frankly we may need more ancient samples from his timeline and area to make more sense of this find.

I personally find it implausible that this is the same affinity found in Early European Farmers given that Haak et al. itself did a study on the Steppe, relatively not too far off from Kostenki14's location and none of the Eastern European Hunter-Gatherers in the area prior to the arrival of Armenian-like West Asian ancestry in the area showed signs of Basal Eurasian admixture, Western European Hunter-Gatherers across the rest of Europe west of the Pontic-Caspian Steppe also show no signs of such admixture until mixture with the Early European Farmers whose genome is predominantly West Asian ensued.

Anyway, all that can be said at this point is that further study is required & I suppose this is intriguing to say the least.

Reference List:

2. Genomic structure in Europeans dating back at least 36,200 years, Seguin-Orlando et al. 2014


1. You're welcome to see the author of Eurogenes' take on all this from months ago...

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