SMBE 2012

By Razib Khan | June 24, 2012 7:34 pm

Dienekes has summaries up of human-related abstracts of Society for Molecular Biology & Evolution 2012.

1) Remember these are not papers, and some of the abstracts may never become papers, at least in recognizable form

2) Speaking of which, Estimating a date of mixture of ancestral South Asian populations:


Linguistic and genetic studies have demonstrated that almost all groups in South Asia today descend from a mixture of two highly divergent populations: Ancestral North Indians (ANI) related to Central Asians, Middle Easterners and Europeans, and Ancestral South Indians (ASI) not related to any populations outside the Indian subcontinent. ANI and ASI have been estimated to have diverged from a common ancestor as much as 60,000 years ago, but the date of the ANI-ASI mixture is unknown. Here we analyze data from about 60 South Asian groups to estimate that major ANI-ASI mixture occurred 1,200-4,000 years ago. Some mixture may also be older—beyond the time we can query using admixture linkage disequilibrium—since it is universal throughout the subcontinent: present in every group speaking Indo-European or Dravidian languages, in all caste levels, and in primitive tribes. After the ANI-ASI mixture that occurred within the last four thousand years, a cultural shift led to widespread endogamy, decreasing the rate of additional mixture.

To comments on this. The ~1,200 estimate for large-scale admixture is just nearly impossible to credit. Historically the only group which are likely candidates for this would be the Jatts of Punjab, who have myths of descents from the last pre-Islamic Central Asian populations which intruded upon the Indian subcontinent. In fact, if 1,200-4,000 represents an interval, the expected value is ~2,600 years ago. Approximately the time of the Buddha. This seems rather too recent to be plausible. But…the authors do note that there may be older admixture events. If the signal they’re picking up is the Indo-Aryan expansion, then that is somewhat plausible, in that it seems that as lage as that period large swaths of the eastern Indo-Gangetic plain and much of Central India were in the process of becoming part of greater Aryavarta.

  • http://dispatchesfromturtleisland.blogspot.com ohwilleke

    “If the signal they’re picking up is the Indo-Aryan expansion, then that is somewhat plausible, in that it seems that as lage as that period large swaths of the eastern Indo-Gangetic plain and much of Central India were in the process of becoming part of greater Aryavarta.”

    Also, if on “day one” of Indo-Aryan expansion into a particular region there is zero ANI-ASI admixture, it could easily take a thousand years for the stable equilibrium admixture percentages that might be represented by a 2,600 year old admixture date to be realized.

    Admixture is frequently modeled as a point event, but at ancient historic era time scales, the length of time during which admixture is happening relative to the relative age of the event is material.

    A suspect that a typical admixture event probably follows something like an S shaped logistic curve.

  • Balaji

    Large scale ANI/ASI admixture is likely to have happened in Pakistan more recently than 1,200 years ago. Pakistan became predominantly muslim after the Islamic conquest of the Subcontinent and Islamic elites have imported kafir slaves and concubines throughut history causing significant gene flow into Islamic regions. For example the countries of North Africa from Egypt to Morocco have 20 to 30% sub-Saharan admixture a significant amount of which is likely due to this practice. Similarly a good part of the approximately 25% ASI in Pakistan is likely due to the importation of slaves and concubines from India. In fact ANI/ASI admixture in Pakistan continues to this day as the Muhajir migrants from the partition of India integrate into the Pakistani population.

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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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