I shall come on this topic at the week end;
as the topic is about Basques, ancient or current ones, I put here some thoughts of Eurogenes-Davidski (Polako?)
Friday, October 16, 2015
Basques are not simply a fusion of Iberian hunter-gatherers and early farmers
I thought I'd revisit the issue of Basque origins with my new Principal Component Analysis (PCA) of West Eurasia. The useful thing about this PCA is that it gets around two problems that routinely affect PCA featuring ancient samples: projection bias, otherwise known as shrinkage, and exaggerated outcomes for individuals with high counts of homozygous genotypes.
A couple of recent papers argued that Basques were the direct descendants of local hunter-gatherers and early Neolithic farmers who arrived in Iberia from the eastern Mediterranean. This is probably correct for the most part, but it doesn't tell the whole story.
On the PCA above, Basques are quite distinct from Early Neolithic, Middle Neolithic and Copper Age Iberians (marked Iberia_EN, Iberia_MN and Iberia_CA, respectively), because they are significantly more eastern. In fact, they cluster with the only Bronze Age Iberian on the plot (Iberia_BA), which is the same individual that I found to harbor steppe-related ancestry (see
here).
Thus, the story told by the PCA is that Basques are the progeny of Bronze Age Iberians, who, unlike their Copper Age predecessors, experienced a pulse of steppe-related admixture from the east.
Formal statistics back this up. For instance, here's a quote from the recently revised
Mathieson et al. preprint:
However, the statistic f4(Basque, Iberia_Chalcolithic; Yamnaya_Samara,Chimp)=0.00168 is significantly positive (Z=8.1), as is the statistic f4(Spanish, Iberia_Chalcolithic; Yamnaya_Samara, Chimp)= 0.00092 (Z=4.6). This indicates that steppe ancestry occurs in present-day southwestern European populations, and that even the Basques cannot be considered as mixtures of early farmers and hunter-gatherers without it (4).
The key question now is who brought the steppe-related ancestry to Basque country. Were they Indo-Europeans or speakers of Proto-Basque? Also, did they actually come from the steppe, or somewhere nearby, like the Carpathian Basin?
The reason I mention the Carpathian Basin is because, as per the PCA, Basques more or less cluster between Copper Age Iberians and some of the Bronze Age Hungarians (marked Hungary_BA). But this is just one possibility, and I'm not sure at this stage how plausible it looks with, say, formal statistics.
In this analysis I used samples from the
Allentoft et al.,
Gunther et al.,
Haak et al. and
Lazaridis et al. datasets, all of which are publicly available. The latter two are found at the Reich Lab site
here. If you're confused by some of the acronyms in the PCA key, see
here.
Posted by
Davidski
[FONT=monospace, serif]ATP2 ATP3 ATP7 ATP9 ATP12 ATP16 ATP17 ATP20[/FONT]
[FONT=monospace, serif]Neolithic European 80.38 49.49 88.17 67.83 82.82 90.82 99.53 54.34[/FONT]
[FONT=monospace, serif]Gravettian 10.29 12.62 11.82 28.38 0.00 2.30 0.00 0.00[/FONT]
[FONT=monospace, serif]Aurignacian 8.42 3.83 0.00 2.53 17.17 6.36 0.45 10.46[/FONT]
[FONT=monospace, serif]Northern Mideastern 0.00 30.39 0.00 0.00 0.00 0.00 0.00 0.00[/FONT]
[FONT=monospace, serif]Veddoid-Caucasoid 0.00 0.00 0.00 0.14 0.00 0.00 0.00 28.91[/FONT]
[FONT=monospace, serif]Amerindian 0.06 0.00 0.00 0.07 0.00 0.00 0.00 6.28[/FONT]
[FONT=monospace, serif]Northern Mongoloid 0.84 3.66 0.00 0.00 0.00 0.51 0.00 0.00[/FONT]
[FONT=monospace, serif]Australoid 0.00 0.00 0.00 1.04 0.00 0.00 0.00 0.00[/FONT]
[FONT=monospace, serif]Southern Mideastern 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00[/FONT]
[FONT=monospace, serif]Eskimo 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00[/FONT]
[FONT=monospace, serif]Bushman 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00[/FONT]
[FONT=monospace, serif]Taiwanese aborigine 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00[/FONT]
[FONT=monospace, serif]Western Negroid 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00[/FONT]
[FONT=monospace, serif]Southern Mongoloid 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00[/FONT]
[FONT=monospace, serif]Eastern Negroid 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00[/FONT]
[FONT=monospace, serif]Pygmy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
[/FONT]
