Caste and Colour in India : A genomic pointer to the Aryan Invasion/ Migration Theory ??

Caste and Colour in India : A genomic pointer to the Aryan Invasion/ Migration Theory ??

(This post is under revision/ editing/ additions)

NB: I have referred to caste/ colour etc only for the purposes of identification.

In the last few years a number of genomic research projects have been carried out on South Asian populations. In my opinion, two of these stand out in explaining the extant population mix and caste-related physiognomy. The 2 are:

· Genetic Evidence for Recent Population Mixture in India by Priya Moorjani,* Kumarasamy Thangaraj, Nick Patterson, Mark Lipson, Po-Ru Loh,,Periyasamy Govindaraj, Bonnie Berger, David Reich,and Lalji Singh Sept 2013. http://www.sciencedirect.com/sci...

· Genomic reconstruction of the history of extant populations of India reveals five distinct ancestral components and a complex structure by Analabha Basu, Neeta Sarkar-Roy, and Partha P. Majumder (NIBM and ISI Kolkata ) July 2015.http://www.pnas.org/content/113/...

What I am trying to do here is to present the findings from these 2 research studies in layman’s language (and considering that I am myself a layman in genomics, there could be some mistakes)

Before I get on to the findings of the research projects a little background information is in order. A majority of the world’s current population derives from 3 ancestral races/ lineages: Negroid (dark/ dark curly hair/ dark eyes), Mongoloid (pale/ straight dark hair/ slit eyes) and Caucasoid (white / eyes may be light or dark/ hair may be dark or light and straight or curly) . As the names suggest the three lineages have distinct physical features associated with them. I want to clarify that these are ancestral lineages. Existing population groups will exhibit features that may be a combination of the 3 types depending on the degree of historical mixing or isolation.

In addition there is one more lineage, the Australoid (dark/ dark curly hair) which is not very large but of interest to us in India.

The names of the specific genes applicable to the Indian population are Ancestral South Indian (ASI from Negroid)., Ancestral North Indian (ANI from Caucasoid), Ancestral Tibeto Burman (ATB from Mongoloid) and Ancestral Asia Australoid (AAA from Australoid)

Now the main finding of the 2 research studies are do with the admixture of the genes in the current population and the dates when the admixture started and ended.

1. · Existing population groups of India are a mixture of 2 or more of these 4 groups. (no group is 100% pure ie from a single lineage, though some groups have a very high percentage of a single lineage). A table with details is given in the appendix .
2. · There is a distinct pattern of gene admixture depending on caste / tribe and geography.
3. · ASI and ANI and combinations form the largest part of the non-tribal total population with higher castes showing more ANI and lower caste showing more ASI. This is true both for North India as well as South.
4. · There is a reduction of ANI as we move from North India to South India. And a corresponding increase in ASI as we move from North to South.
5. · The ASI/ANI admixture started only approx 4200 years ago. Before that time there was no ASI-ANI admixture.
6. · ASI is exclusive to South Asia, not found elsewhere. ANI is seen in Iran / Afghanistan/ Central Asia.
7. ·While ASI ANI admixture abruptly stopped about 1900 years ago all over India, the ANI-AAA admixture continued for some more time.
8. · AAA is mostly seen in high percentage in tribals of central and eastern India
9. · ATB is more pronounced in the North East.

Now if you put the points above together, you can see a distinct connection between lineage and caste/ tribal status.

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Appendix. (UC =Upper Caste, MC= Middle caste, TR=tribal)

Populations in bold letters are the ones that have a very high percentage of a single lineage...ie very little admixture.