November 07, 2006

Mongoloid components in Eastern Europe

Slavs and other eastern Europeans are typically Caucasoid although one does not seldom find among them individuals with certain attenuated Mongoloid influences. The extent of Mongoloid admixture in eastern Europe will eventually be determined by autosomal admixture studies which sample the relevant source populations of the Mongoloid component in Europe, namely the Uralic and Altaic speakers of Siberia and Central Asia.

At present, the only study which studied the genomic study of a Slavic sample of Russians (Science 20 December 2002: Vol. 298. no. 5602, pp. 2381 - 2385) determined a 93% membership coefficient in the main Caucasoid cluster, with a 3% membership in the main (East Asian) Mongoloid cluster. Unfortunately Central Asian Turkic and Finno-Ugrian populations from Europe and Asia were not sampled.

The presence of Mongoloid mtDNA types in East Europe is well established, but it should be remembered that movements from the east did not usually involve large numbers of women (*). Therefore, one expects that inference from mtDNA will underestimate the total number of immigrants.

Moreover, as I have pointed out before, Turkic speakers of Central Asia were likely to possess majority components of Caucasoid Y chromosomes associated with Mongoloid mtDNA components. Today, haplogroup C chromosomes make up a large component of Y-chromosome variation in Central Asia (including the famous "Genghis Khan" line), but these were probably added (from the east), late in history, since the Mongol expansion is at the end of the great period of Altaic migrations to the west (Huns, Seljuks, Ottomans, Bulgars, etc.)

As a result a proportion of the eastern immigrants into Europe would be undetectable with Y-chromosome markers, namely the substantial fraction with Caucasoid Y chromosomes and Mongoloid mtDNA. The male immigrants of this type would impart their Y chromosomes in the regions they invaded, but not their maternal mtDNA. In the Altai-Kizhi group, for example, 71% Caucasoid Y chromosomes are associated with 76% non-Caucasoid mtDNA.

Consider a population with 3/4 Caucasoid Y chromosomes and 3/4 Mongoloid mtDNA. Consider that the migrant group consists of 3/4 men and 1/4 women. Under such circumstances we would expect approximately the same rate of Mongoloid mtDNA and Y chromosomes in the recipient population. Moreover, the inferred admixture proportion from the frequencies of Mongoloid mtDNA and Y chromosomes would underestimate the true rate of Mongoloid admixture by a factor of 2.

Unfortunately, the presence of Mongoloid Y chromosomes has not been properly studied until now. In the recent Y chromosome study of the Czech Republic for example, the main Mongoloid Y-haplogroups (C, Q, O) likely to have accompanied the women bearing the 3% Mongoloid mtDNA were not examined and could be part of the Y*, P*, and K* paragroups. Similarly, none of these haplogroups were studied in a recent study on Poland and Germany.

In conclusion:
  • The mtDNA evidence suggests a very low-level introgression of Mongoloid components into Eastern Europe.
  • The extent of this admixture is likely to be underestimated by the genetic profile of the source population and the excess of male migrants.
  • The best estimate of the admixture rate will be determined by autosomal studies that sample relevant Uralic-Altaic source populations, but is probably unlikely to amount to more than a few percentage points.
(*) Except in folk migrations such as those of the Kalmyks.

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