500K SNP Europe-wide study of genetic structure
This is a very important study, the first one to use both a large number of markers and a wide and fairly representative sample of Europeans from across the continent.
My main observations after reading this study are:
* relative genetic homogeneity in Europe, with a fairly small percentage of variance explained by geographic differentiation
* clinal, rather than racial apportionment of European genetic variation, with no emerging separated clusters (except the Finns, who stand at some distance along the first eigenvector)
* south-north (but not east-west) decrease in genetic variation and heterozygosity indicating that Europe was populated on a south-north axis, rather than an east-west one.
* clear clustering of individuals from different ethnic groups within the European continuum, indicating that ethnic groups are not only cultural, but to some extent biological entities.
* Some ethnic groups are clearly distinguishable from each other (e.g. Swedes vs. Spaniards); some groups are partitioned into fairly disjoint sets (Spain I vs. Catalans in Spain II); others mutually overlap (e.g., British and Irish); while others overlap asymetrically (e.g., some former Yugoslavs in the Greek cluster, but not vice versa).
Regarding the Greeks (from the northern part of the country), their closest neighbors are the two Italian groups (IT1 and IT2 (Marches)) on the one side, and former Yugoslavs on the other.
Interestingly Italians neighbor Spaniards on the other side; whereas former Yugoslavs neighbor Czechs.
A straightforward explanation for this pattern is that the Italian groups has mixed Western and Eastern Mediterranean affiliations; the latter stemming from either Neolithic farmers or Greek (or Etruscan, etc.) colonists.
Former Yugoslavs are mostly disjoint from Greeks, except some who seem to be Slavicized Greeks, consistent with their descent from indigenous Balkan populations on one hand and Slavic immigrants more akin to Czechs and Poles on the other. Thus, they occupy an intermediate position between Greeks and Czechs.
From the paper:
Hierarchical analysis of molecular variance (AMOVA) [17]
revealed that clustering the individuals according to four geographic
groups—north (NO, SE, FI), north-west/central (IE, UK,
DK, NL, DE1, DE2, AT, CH, FR), east (HU, RO, PO, CZ), and
south (PT, ES1, ES2, IT1, IT2, YU, EL)—explained an average
of 0.17% (95% coefficient interval: 0.0% to 0.91%) of the total
genetic variance, whereas individual subpopulation affiliation
explained 0.25% (95% coefficient interval: 0.0% to 1.25%).
Overall, our study showed that the autosomal gene pool in
Europe is comparatively homogeneous but at the same time
revealed that the small genetic differentiation that is present
between subpopulations is characterized by a significant
correlation between genetic and geographic distance. Furthermore,
the qualitative nature of these results is in close agreement
with expectations based on human migration history in
Europe. The major prehistoric waves of human migration in
Europe followed south and southeastern to north and northwestern
directions [1], including the first Paleolithic settlement
of the continent by anatomically modern humans [18], most of
the postglacial resettlement during the Mesolithic [19], and the
farming-related population expansion during the Neolithic [18,
20]. Thus, both the level and the change in neutral autosomal
variation in Europe can be expected to roughly follow southernto-
northern gradients as we observed, with the possible exception
of population isolates as observed for the Finns.
Genetic Map of Europe
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Originally Posted by Sphere
