An important preprint has just appeared at bioRxiv. the item includes ancient DNA via four Estonian Corded Ware Culture (CWC) individuals via two different sites. These CWC samples belong to Y-haplogroup R1a-Z645, which can be the most common type of R1a inside the planet today, including South Asia, despite a relatively recent coalescent time of 5,400 yr BP. One of the samples can be further classified as belonging to R1a-Z283. Almost 100% of the modern-day Eastern as well as Central European R1a belongs to This specific subclade.
The brand-new data also includes an Comb Ceramic Culture (CCC) male that will belongs to R1a5-YP1272. This specific might be an extinct line, or one that will can be at This specific point extremely rare in Eastern Europe. via the paper:
All four of the Estonian CWC individuals could be assigned to the R1a-Z645 sub-clade of hg R1a-M417 which together with N can be one of the most common Y chromosome haplogroups in present-day Estonians (33%)  . Importantly, This specific R1a lineage can be only distantly related to the R1a5 lineage we found inside the CCC sample. The finding of high frequency of R1a-M417 in Estonian CWC samples can be consistent with the observations made for some other Corded Ware sites that will, along with Late Bronze Age remains associated with Sintashta Culture, also show high frequency of hg R1a-M417 [2,25]. … The coalescent time for the R1a-Z645 clade, estimated via modern data at 5,400 yr BP (95% CI 4,950–6,000) 43 , predates the time when the CWC individuals carrying the R1a-Z645 lineages lived in Estonia (4,000–4,800 yr BP). The fact that will all four of the CWC male individuals via two distinct sites in Estonia belonged to This specific recently expanded R1a branch, different via the one carried by CCC, suggests that will admixture between CWC farmers as well as CCC hunter-gatherers may have been limited at least inside the male lineages during the early stages of farming in Estonia.
at This specific point, can anyone explain to me how the authors came to This specific conclusion? Was the item based on their ADMIXTURE output?
Furthermore, the presence of a genetic component associated with Caucasus hunter-gatherers as well as later with people representing the Yamnaya Culture in Eastern hunter-gatherers as well as Estonian CCC individuals means that will the expansion of the CWC cannot be seen as the sole means for the spread of This specific genetic component, at least in Eastern Europe.
If the item can be indeed based on ADMIXTURE, then they genuinely need to back the item up with some robust formal stats as well as qpAdm, because ADMIXTURE can be not a formal mixture test. Moreover, they used the projection (P) option in their ADMIXTURE analysis. I’m not a huge fan of This specific option when running fine scale intra-continental analyses, because I find that will the item usually results in severe projection bias. In some other words, the test samples are treated differently via the reference samples, as well as essentially show results that will they shouldn’t. Speaking of projection bias, I’m quite certain that will their Principal Component Analysis (PCA) suffers via the item. The ancient samples look like they’re being pulled into the middle of the plot, so much to ensure that will one of the foragers basically clusters with modern-day Lithuanians, while the CWC individuals appear too western. They need to fix This specific.
I do note that will the authors used the lsqproject option when running their PCA. A lot of people assume that will once they do This specific they’ve taken care of projection bias. This specific can be not so. lsqproject doesn’t solve This specific problem; the item just makes sure that will missing markers don’t skew the projection. Citation… Saag et al., Extensive farming in Estonia began through a sex-biased migration via the Steppe, bioRxiv, March 2, 2017, doi: https://doi.org/10.1101/112714
Baltic Corded Ware: rich in R1a-Z645