The claim that the Proto-Indo-Europeans came from West Asia and largely belonged to Y-haplogroup J2 seems to be popular online nowadays. I won't discuss here in detail the reasons why, but suffice to say it has a lot do with aggressive lobbying on several online forums and blogs by a few people of Southern European extraction, like Dienekes Pontikos.
It was always a shaky proposition, but difficult to debunk thoroughly. Until now.
Thanks to recent advances in both modern and ancient DNA research, we can now safely say that Y-haplogroup J2 was not involved in any rapid, large scale population expansions during the Late Neolithic/Early Bronze Age (LN/EBA), the generally accepted Proto-Indo-European time frame.
It thus fails to meet even the most basic criteria of a Proto-Indo-European diagnostic marker. The Proto-Indo-Europeans, after all, were surely highly patriarchal and patrilineal, and therefore expected to have left a clear signal of their migrations in the Y-chromosomes of many present-day Indo-European speakers.
For instance, an analysis of data from the deep sequencing of human Y-chromosomes as part of the 1000 Genomes Project suggests that not a single major subclade of J2 began expanding even roughly close to the LN/EBA. See here.
In the plot above three lineages jump out at you. E1b, R1a, and R1b. The first is associated with the Bantu expansion, that occurred over the last 4,000 years. The second two are likely associated with Indo-Europeans in both Asia and Europe, respectively. The timescale is on the order of 4 to 5,000 years in the past. The association between culture and genes, or the genetic lineages of males, is rather clear, in these cases. In other instances the growth was more gradual. For example, the lineages likely associated with the first Neolithic pulses, J and G.
Moreover, not a single instance of J2 has been reported from remains classified as belonging to the Andronovo, Battle-Axe, Corded Ware, Khvalynsk, Poltavka, Potapovka, Sintashta, Srubnaya and Yamnaya archaeological cultures. In other words, Kurgan and Kurgan-derived groups generally accepted to be early Indo-European, whch is a view that now has very strong support from ancient genomics. See here and here.
To date, most of these samples have probably come from elite burials. So at some point, when many more non-elite samples are sequenced, we are likely to see J2 among a few supposedly early Indo-European individuals. But so what?
There might be a couple of ways to salvage the Proto-Indo-Europeans = J2 theory. We'd have to argue that...
- the Proto-Indo-European time frame was actually the early Neolithic
and/or
- the Proto-Indo-Europeans were a small group that Indo-Europeanized the steppe Kurgan people, perhaps mainly via female migrations, and then did not partake in the main early Indo-European expansions
But the former is not particularly clever when viewed in the context of historical linguistics data. See here.
For instance, almost all IE language branches testify to a word designating ‘wool’. Since archaeological evidence suggests that wool sheep did not exist until the beginning of the fourth millennium BCE, the existence of the word in PIE would indicate that the disintegration of the proto-language could not have taken place before this date. Similarly, words for concepts such as ‘wheel’, ‘yoke’, ‘honey bee’ and ‘horse’ may be correlated directly with concrete, datable archaeological evidence.
And the latter isn't very parsimonious, and to me looks like special pleading. Why even bother?
