Genetic History of Europe - Relation Between Europeans and Other Populations

Relation Between Europeans and Other Populations

Percentage genetic distances among major continents based on 120 classical polymorphisms

	Africa	Oceania	East Asia	Europe
Oceania	24.7
East Asia	20.6	10
Europe	16.6	13.5	9.7
America	22.6	14.6	8.9	9.5

According to Cavalli-Sforza's work, all non-African populations are more closely related to each other than to Africans; supporting the hypothesis that all non-Africans descend from a single old-African population. The genetic distance from Africa to Europe (16.6) was found to be shorter than the genetic distance from Africa to East Asia (20.6), and much shorter than that from Africa to Australia (24.7). He explains:

...both Africans and Asians contributed to the settlement of Europe, which began about 40,000 years ago. It seems very reasonable to assume that both continents nearest to Europe contributed to its settlement, even if perhaps at different times and maybe repeatedly. It is reassuring that the analysis of other markers also consistently gives the same results in this case. Moreover, a specific evolutionary model tested, i.e., that Europe is formed by contributions from Asia and Africa, fits the distance matrix perfectly (6). In this simplified model, the migrations postulated to have populated Europe are estimated to have occurred at an early date (30,000 years ago), but it is impossible to distinguish, on the basis of these data, this model from that of several migrations at different times. The overall contributions from Asia and Africa were estimated to be around two-thirds and one-third, respectively". —

This particular model used an Out of Africa migration 100,000 years ago which separated Africans from non-Africans followed by a single admixture event 30,000 years ago leading to the formulation of the European population. The admixture event consisted of a source population that was 35% African and 65% East Asian. However the study notes that a more realistic scenario would include several admixture events occurring over a sustained period. In particular they cite the spread of farming from a source population in West Asia 5000–9000 years ago may have played a role in the genetic relatedness of Africans and Europeans since West Asia is sandwiched in between Africa and Central Asia. The model assumed an out of Africa migration 100kya and a single admixture event 30kya. However, most contemporary studies have more recent dates that place the out of Africa migration 50-70kya. The study also involved a direct comparison between Sub-Saharan Africans (Central Africans and Senegalese) and Europeans. North Africans population were omitted from the study as they are known to have both Eurasian and Sub-Saharan admixture. These considerations might help explain the apparent short genetic distance between Europeans and Africans

A later study by Bauchet, which utilised ~ 10 thousand autosomal DNA SNPs arrived at similar results. Principal component analysis clearly identified four widely dispersed groupings corresponding to Africa, Europe, Central Asia and South Asia. PC1 separated Africans from the other populations, PC2 divided Asians from Europeans and Africans, whilst PC3 split Central Asians apart from South Asians.