R1a1a, what is best in life?

300px-R1a1a_distributionOver at Greg Cochran’s blog he’s been posting on Indo-Europeans. He’s had many of these ideas for a long time, but after I recounted to him some more information from ASHG 2014 it crystallized a lot in terms of specifical detail. For example, the Kalash of Pakistan share a lot of drift with “Ancestral North Eurasians” (ANE). By “a lot”, I mean in the same range as North Caucasus and Eastern European groups. Other HGDP samples from Pakistan are somewhat lower in their signals, but it still noticeable.* In Iosif Lazaridis’ presentation at ASHG 2014 he outlined the likelihood that the widespread distribution of ANE ancestry in Europe probably had something to do with the migrations of the Yamna culture, from which derived the Battle Axe Culture. The genetic variation you see in eastern and central Europe today is representative of the Yamna people. They know because they have ancient samples from those regions. The Yamna themselves are a mix of an Armenian-like Middle Eastern population, and “Eastern Hunter-Gatherers” (EHG) which resemble those to the west but have a higher fraction of ANE (so the are WHG + ANE, while the Armenian-like population is similar to, but not exactly the same as, the “European First Farmers” (EFF).

But that’s not the point of this post. There were two Y chromosome posters which were of interest. One showed a Bayesian skyline plot which illustrated that many of the Y chromosomal lineages you know and love went through very rapid population expansion on the order of 5 to 10 thousand years ago. A second poster had a phylogeny of Y chromosomes derived from high coverage whole genome sequencing. They had four individuals from the R1 lineages, two of them from R1a1a. One individual was Indian and the other was Russian. The coalescence was ~5,000 years ago. The individual who did this analysis was not aware of the Bayesian skyline plot poster, so she immediately ran off to look at it when I told her. The coalescence with R1b for the R1a individuals was ~10,000 years ago.

I know that there are lots of debates about clocks and calibration when it comes to Y chromosomes. But the archaeology, ancient DNA, autosomal work, and uniparental lineages are all coming together with a coherent picture. The Y chromosomal data strongly suggests that we’re talking about “star phylogenies” in the recent human male past.

* And for what it’s worth the Kalash are not descended from the soldiers of Alexander. Rather, they seem an early example of the admixture which led to modern South Asians. Their drift from other populations is due to them being isolated and endogamous.

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