Epic fail

This is the somewhat dubious conclusion from a new paper by Balanovsky et al. at Human Genetics dealing with, amongst other things, the Y-chromosomes of the Early Bronze Age Yamnaya people:

The currently available dataset does not contradict the hypothesis that R-GG400 marks a link between the East European steppe dwellers and West Asians, though the route and even direction of this migration is disputable. It does, however, demonstrate that present-day West European R1b chromosomes do not originate from the Yamnaya populations analyzed in (Haak et al. 2015; Mathieson et al. 2015) and raises the question of their origin. A Bronze Age origin is more likely than a Neolithic one (Balaresque et al. 2010), but further ancient DNA studies may be necessary to identify this source.

More to the point, the authors are trying to argue the following two rather far-fetched and tenuous positions:

- R1b-GG400, the most common Y-haplogroup in Yamnaya samples sequenced to date, moved into Eastern Europe from West Asia, and therefore the Indo-European homeland was in West Asia

- there was no massive Kurgan expansion deep into Europe from the Pontic-Caspian Steppe, because the most common type of R1b in much of Europe is R1b-L51 and not R1b-GG400.

What they're ignoring is that a wide range of European Upper Paleolithic and Mesolithic foragers, mostly from Eastern Europe, belong to R1b, including R1b-P297, the ancestral lineage to both R1b-GG400 and R1b-L51 (see here and here). On the other hand, not a single West Asian forager or even Neolithic farmer as yet belongs to R1b (see here).

Hence, even though it's still possible that R1b-GG400 moved into Eastern Europe from West Asia, it's no longer a parsimonious or convincing theory because it's contradicted by direct evidence from currently available ancient DNA.

The authors are also ignoring very solid evidence from genome-wide data that Yamnaya, or closely related populations from the Pontic-Caspian Steppe, contributed in a big way to the ethnogenesis of modern-day Europeans. Considering that R1b-L51 is a sister clade of R1b-GG400, it's only logical to think that it could have been one of the main Y-chromosome haplogroups associated with this event.

The paper has some nice data and maps, but it's an epic fail as a whole, because it's basically an exercise in confirmation bias.

Citation...

Balanovsky, O., Chukhryaeva, M., Zaporozhchenko, V. et al., Genetic differentiation between upland and lowland populations shapes the Y-chromosomal landscape of West Asia, Hum Genet (2017). doi:10.1007/s00439-017-1770-2