Gene Expression

If you read this weblog you are aware that I have a fascination with the intersection of human history and human evolutionary genetics. There are many questions I have about the finding from evolutionary genomic studies that light skin evolved at least twice independently in Eurasia within the last 20,000 years or so at the extremities. The selection coefficients are large, so I am confused as to why even minimal gene flow did not result in equilibration and homogenization of the allelic profiles of the populations. I have posited that the answer has to do with very low population densities verging upon nil in Central Asia. From The Horse, the Wheel, and Language: How Bronze-Age Riders from the Eurasian Steppes Shaped the Modern World (a book I can not recommend enough!):

…On the Ukok plateau, where the early Afanasievo cemetery at Bertek 33 was found, the Afanasieva immigrants occupied a virgin landscape-there were no earlier Mesolithic or Neolithic sites. Afanasievo sites also contained the earliest bones of domesticated cattle, sheep, and horses in the Altai.

Cemeteries of the local Kuznetsk-Altai foragers like Lebedii II were located in the forest and forest-meadow zone higher up on the slopes of the Altai….

i-512db7ad86f577e632d4fe263373b254-ukok.jpgThe Ukok Plateau is about 2000 kilometers from the Ural-Volga regions from which the Afanasievo likel originated. It seems that around 3500 BCE they “leap-frogged” across what would become the northern Kazakh steppe for the pine forests of south Siberian fringe. The point though is this: this sort of volkswanderung only became possible with the emergence of the nomadic herder lifestyle. The selective sweeps which one infers from evolutionary studies likely occurred before the Afanasievo trek….

Related: The Horse, the Wheel, and Language: How Bronze-Age Riders from the Eurasian Steppes Shaped the Modern World.

Comments

  1. #1 Luis
    April 26, 2008

    …the answer has to do with very low population densities verging upon nil in Central Asia.

    Certainly, specially north of the “oasis area” of Uzbekistan and neighbours. This does not just apply to IE expansion eastward but also to Turco-Mongol expansion westward later on. Kazakhs apparently are surprisingly low in Western genetics and that can only be explained because of those extremely low population densities in the steppe and semideserts that constitute that country, that allowed Turco-Mongols to replace almost totally whatever peoples were there before.

  2. #2 razib
    April 26, 2008

    This does not just apply to IE expansion eastward but also to Turco-Mongol expansion westward later on. Kazakhs apparently are surprisingly low in Western genetics and that can only be explained because of those extremely low population densities in the steppe and semideserts that constitute that country, that allowed Turco-Mongols to replace almost totally whatever peoples were there before.

    hm. there’s no signature of pre-turco-mongol ancestry in the kazakhs? i know there is among the uzbeks and what not (seeing as the tajiks and groups like the yangbonis are still around).

  3. #3 Luis
    April 27, 2008

    there’s no signature of pre-turco-mongol ancestry in the kazakhs?

    There is but it’s a lot lower than in neighbours like Uzbekistan. Of all former USSR Central Asia, Kazakhs seem the least “westerner” (and more “easterner”) of all (maybe together with little Kirgizisan), and the difference is very marked.

    I’ve seen some other stuff that goes in the same line but the handiest example may be the Mc Donalds’ world maps (2005), where Kazaks are like 50% “easterner” (mostly C, but also O and Q), while Uzbeks are only like 15% that. Such contrast can’t but be caused by the difference of density in the semidesertic Kazakhstan and the more hospitable Uzbekistan, settled since at least Neolithic times.

    The difference is even more marked if you look at haplogroup R (thought to be associated with the previous rulers of the area: the Indoeuropeans): Kazakhs are like 5% R, while Uzbeks are like 25% (in both cases R1a makes up the larger share). Instead, if you look at clades like J or H, the difference is irrelevant (what might mean they are a recent Silk Road arrival or that they were shared by groups not displaced by the Turks).

  4. #4 Pastoral Nomad
    April 29, 2008

    And not just there:

    Y-chromosomal haplogroups composition and frequencies were analyzed in Northern and Southern Altaians. In the gene pool of Altaians a total of 18 Y-chromosomal haplogroups were identified, including C3xM77, C3c, DxM15, E, F*, J2, I1a, I1b, K*, N*, N2, N3a, O3, P*, Q*, R1*, R1a1, and R1b3. The structured nature of the Altaic gene pool is determined by the presence of the Caucasoid and Mongoloid components, along with the ancient genetic substratum, marked by the corresponding Western and Eastern Eurasian haplogroups. Haplogroup R1a1 prevailed in both ethnic groups, accounting for about 53 and 38% of paternal lineages in Southern and Northern Altaians, respectively. This haplogroup is thought to be associated with the eastward expansion of early Indo-Europeans, and marks Caucasoid element in the gene pools of South Siberian populations. Similarly to haplogroup K*, the second frequent haplogroup Q* represents paleo-Asiatic marker, probably associated with the Ket and Samoyedic contributions to the Altaic gene pool. The presence of lineages N2 and N3a can be explained as the contribution of Finno–Ugric tribes, assimilated by ancient Turks. The presence of haplogroups C3xM77, C3c, N*, and 03 reflects the contribution of Central Asian Mongoloid groups. These haplogroups, probably, mark the latest movements of Mongolian migrants from the territory of contemporary Tuva and Mongolia. The data of factor analysis, variance analysis, cluster analysis, and phylogenetic analysis point to substantial genetic differentiation of Northern and Southern Altaians. The differences between Northern and Southern Altaians in the haplogroup composition, as well as in the internal haplotype structure were demonstrated.

    http://www.unboundmedicine.com/medline/ebm/record/17633562/full_citation/%5BGene_pool_differences_between_northern_and_southern_Altaians_inferred_from_the_data_on_Y_chromosomal_haplogroups%5D

  5. #5 Luis
    April 30, 2008

    Certainly Altai is, like Uyghuristan, an eastern pocket of partly western ancestry (assuming R1a is “western”, as it’s also very high in South Asia – but yes: I tend to accept the Kurgan model as very valid).

    But haplogroup N needs not to be Finno-Ugric at all. That’s only in Europe (and maybe Western Siberia). N has a wide distribution mostly through Northern Eurasia and it is markedly strong also among Mongols (specially “old Mongols”, like Buryats), among other Siberian peoples. N is also found in lesser ammount, but occasionally with high diversity, in East Asia and it’s directly related to typical East Asian haplogroup O. So your conclussions in this aspect are surely wrong. Most probably Fino-Ugric ethnicity was formed at the Urals, maybe in direct correlation (but diferent male ancestry lines) with the formation of Indo-European one (it’s been posited once and again that Uralic and IE languages are related or at least were for long in intimate sprachbund, what is coincident with what we know of their adjacent archaeological urheimats).

  6. #6 Pastoral Nomad
    May 1, 2008

    Haplogroup N is not N1c or N1b, as it is stated in the abstract:

    “”The presence of haplogroups C3xM77, C3c, N*, and 03 reflects the contribution of Central Asian Mongoloid groups.””

  7. #7 David Marjanovi?
    May 9, 2008

    Be very, very, very careful in correlating genes to languages. They are not inherited the same way.

    yangbonis

    Yaghnobi. An Iranian language, considered the descendant of Sogdian.

  8. #8 bursa evden eve nakliyat
    March 28, 2009

    but also O and Q), while Uzbeks are only like 15% that. Such contrast can’t but be caused by the difference of density in the semidesertic Kazakhstan and the more hospitable Uzbekistan, settled since at least Neolithic times

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