The Mesolithic expansion of haplogroups R1a and R1b

When I was checking out those possible R1b-L754 from Arabia, I noticed again the Villabruna-related sample Iboussieres31-2 (ca. 10090-9460 BCE, layer date based on a direct date of Iboussieres39), of mtDNA U5b1, originally reported as of Y-DNA hg. R.

It was later reported as of hg. R1b-L754 based on a derived call for FGC35, listed on ISOGG, but which is neither on the FTDNA nor YFull tree. In fact, the sample is negative for PF6271 (1x G->A), a L754 equivalent.

Based on the currently agreed upon reliable SNPs, it should thus probably be described as Y-DNA R1(*?; xBY14355; xL754?; xPF6292).

The recent Saag et al. (2021) have reported the first evidence for EHG ancestry in northwestern Russia, close to the time it was populated, in the Veretye sample PES001 from Peschanitsa (ca. 10785–10626 calBC), of mtDNA U4a1, Y-DNA R1a-YP1301(pre-YP1272?).

The description of EHG as a mixture of a WHG-like population with an ENA-like, where ENA expansion might have been mediated by different Q lineages (as suggested by Afontova Gora), could suggest an eastward expansion of R1 subclades from Central Europe with post-Swiderian migrations, including R1a-YP4141 in Mesolithic Ukraine and R1a-M459 found later in Neolithic SE Europe; R1b-PF6323 in Early Mesolithic SE Europe; and R1b-pre-V1636 and likely M269 in the Neolithic Middle Volga.

The map of spreading of Post-Swiderian and Post-Krasnosillian sites in Mesolithic of Eastern Europe in the 8th millennia BC. Image from Zalizniak (2017).

This is in line with the traditional accounts (cf. Zalizniak 2017) of a Mesolithic European substrate in the North-Eastern Technocomplex, hence to post-Swiderian expansion of WHG-related communities potentially featuring both hg. R1a and R1b apart from I.

NOTE. The previously reported R1a samples in Moussa et al. (2016), from the Cis-Baikal area, can be discarded – hence any closer connection to the east or the west – since this haplogroup has not been found among many other samples from the area, and the authors seem unable or unwilling to repeat the analysis. On the other hand, the R1b-BY14355 (“pre-PH155”) branch appears first among Neolithic WSHG-like populations from Central Asia, which is compatible with both, an eastern origin of R1b phylogeny, but also a western one, similar to M73 subclades currently found in Asia.

On the other hand, the ancestral call for L754 in Iboussieres31-2 is subjected to deamination and hardly reliable, based on the much older Villabruna sample; there is no call for SNPs defining the levels R1b, L389, L389>P297, L389>V1636, or PF6323; and even if it were a reliable basal R1*, inferring anything from the few samples spanning millennia of Palaeolithic and Mesolithic populations of Northern Eurasia is risible. For all we know, there might have been a million population movements in any direction since the Mal’ta Buret sample of hg. R*.

But, still interesting to keep in mind a potential Western European Mesolithic R1*, in case Swiderian and post-Swiderian samples bring surprises.