R1a1a update: there's something special about the Southern Baltic

A very coherent picture is emerging of the genetic history of Central and Eastern Europe, based on Y-DNA, autosomal DNA and craniofacial studies (see links below). One of the major discoveries has been the high diversity of the Y-chromosome haplogroup R1a1a in the Southern Baltic region, centered on modern-day Poland. This area harbors inflated frequencies of a number of R1a1a clades, defined by newly discovered SNPs and/or STR haplotypes (see here). Indeed, the diversity of R1a1a here is much greater than I ever expected to see. Interestingly, it's also a zone of extreme genetic homogeneity, with little admixture from other parts of Eurasia. I would say that it shows no important post-Neolithic influence from Asia. Even the minimal Siberian input in this part of Europe seems to date back to the Neolithic (see here).

This is all very important, because it defines the Southern Baltic region as a major hotspot for R1a1a differentiation and expansion. The other option, of course, is that there were multiple waves of migrations into this area from the late-Neolithic until historic times, which somehow didn't impact on the autosomal character of the native populations. Moreover, the large variety of related R1a1a types brought by these migrations would've had to plummet in frequency, or even go extinct, everywhere else. That seems extremely unlikely.

Based on the information I've picked up to date, the two R1a1a clades to watch are R1a1a1i (Z280+) and R1a1a1h (Z93+). These paternal lines appear to be signals of multiple migrations from West Eurasia to the east, as far as present day Mongolia and South Siberia. It seems the European Z280 took the northern route, while the West Asian Z93 moved across the south. Associating such markers with specific groups is always tricky, but I'd say that Z280 will probably turn up in the North Europid Andronovo skeletons, once they are tested accordingly. I also expect to see it in remains from the Corded Ware culture of Central and Eastern Europe, which has been described by archeologists as partly ancestral to the Andronovo tribes. I have little clue about Z93 in this context. Perhaps it was part of the genetic makeup of the Indo-Aryans? But I can't see that being confirmed anytime soon, because ancient DNA from that part of the world might be difficult to extract, due to the warm climate.

To complicate matters, it appears that later groups moving from the east "picked up" R1a1a along the way, and brought it back to West Asia and Europe. For instance, Z93 is showing a very high correlation with Turkic groups. Moreover, the Turks moved west along both the southern and northern routes mentioned above, and most likely erased much of the Z280 in the steppe zone. I've put together two maps that try and explain what took place. It's early days yet, but I'm very confident this version of events will be confirmed beyond any doubt in the near future with more extensive data, hopefully including full genome sequences of the Andronovo mummies.






As far as I know, the recently completed full genome sequences of a Russian and German both carried R1a1a1i-Z280. That was obviously a coincidence, but it's fascinating how Z280 keeps popping up in samples from across the former Corded Ware zone.

See also...

European admixture in ancient East Asians (aka. two-rooted canines carried by early Indo-Europeans to China)

Poland's genetic links to the ancient Indo-Europeans

The kurgan invasion of Europe...or was that the Corded Ware expansion from Europe?

Horse genetics and the Indo-European and Altaic expansions

Ancient Siberians carrying R1a1 had light eyes

Craniometric links between Central European Funnelbeaker folk and early Indo-European steppe tribes