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Around 70 generations ago, Indians stopped inter-marrying and created endogamous caste groups.

Among the most exciting discoveries in recent years has been in the field of genetics and genomics, as the deciphering of the Indian genetic code has yielded fascinating insights into, “Who We Are and How We Got Here”. That’s the title of Harvard scientist David Reich’s recent book on human origins as pieced together from our DNA.

I may be biased, but the chapters about India — based on the work of Priya Moorjani, K. Thangaraj, Lalji Singh, Vagheesh Narasimhan and numerous other collaborators — are the most fascinating. Over the past decade, these scientists have uncovered compelling evidence showing that most people in India arose from a mixture of two ancestral populations that they call Ancestral North Indian (ANI) and Ancestral South Indian (ASI), and that the ANI component tends to be higher among upper-caste and northern Indians. Other researchers have added greater detail to the picture, showing that in addition to ANI and ASI, Andaman and Nicobar Islanders, Tibeto-Burmans and Austro-Asiatic groups contribute to the great Indian population mix.


Also read: Are Dalit women less or more mobile than upper caste women in India? Jatis hold the answer


Of course, the biggest mystery that ancient DNA can help solve is identifying the Harappans and telling us what happened to them. One 4,500-year-old skeleton from Rakhigarhi is proving to be crucial in this puzzle as the person who it belonged to carried ASI genes, and none from ANI. The coming years will see a lot more discoveries as geneticists and archaeologists get to know each other better, and as polemicists and ideologues reckon with greater and more incontrovertible evidence about our origins.

Here’s what our DNA tells us: More than 4,000 years ago, ANI and ASI didn’t intermarry much. For roughly the next 2,000 years, they widely intermarried, resulting in almost all their descendants (that is, us) being a mixture of ANI and ASI. Then, around 70 generations ago, our ancestors stopped inter-marrying and created endogamous groups that we know as castes. Indians started marrying within their own caste groups around 2,000 years ago.


Also read: Does Rakhigarhi skeleton DNA confirm Dravidian ancestry or reignite Aryan invasion debate?


Who the Harappans were might be of academic and political interest, but the genomics of caste has immense utility for public health and indeed, for how we want to shape our future.

Reich puts it very well. India, he writes, “is composed of a large number of small populations”. He points out that caste groups living side by side in the same village for hundreds of years are two to three times more genetically differentiated compared to people living at the opposite ends of Europe.

Thangaraj and his co-researchers found that of the 263 endogamous groups they studied, more than 81 had greater “identity by descent” scores than the Askhenazi Jews and Finns, among the world’s best-known endogamous groups. Of these, 14 groups had estimated populations of over a million. Now, because certain types of genetic diseases arise because of endogamy — either because people marry close relatives or because they have descended from common ancestors — we can identify and reduce the risk of their occurrence. He cites the example of how diseases like Tay-Sachs syndrome, once widely prevalent among Ashkenazi Jews, have virtually disappeared after the introduction of a community genetic testing programme.


Also read: Address jati, and not just caste, to fix rural welfare schemes like MGNREGA


Potential couples can query a genetic database to know the risks of known genetic diseases in their offspring.

Simple genetic testing is now almost as affordable as an MRI scan. The challenge though is to know what to look for. Ashkenazi Jews have identified a list of diseases that their community is particularly prone to. That list, though, won’t work for other populations. We have around 5,000 endogamous groups in India — which means we need to create 5,000 lists of diseases. To create a list, we must sequence the genomes of 200 individuals from each group and correlate them with observations of genetic diseases prevalent in that community. If we have a national genomic database for all 5,000 communities, a simple genetic test will help uncover any risk of genetic diseases that the individual or couple can expect. Setting up a national genomic database ought to be a part of India’s public health policy.

So, public health is yet another reason to dissolve caste. Inter-caste marriages are a good thing. We, Indians, were forged when the ANI, ASI and others mixed freely for 2,000 years. Then came caste, and divided us into numerous small populations.

Will this change? The bad news is that across India, only 5-6 per cent of marriages are inter-caste. The Indian Human Development Survey, which covers over 42,000 households across India, found that this number hadn’t changed much between 2004-5 and 2011-12. Mizoram (55 per cent), Meghalaya (46 per cent), Sikkim (38 per cent), Jammu & Kashmir (35 per cent) and Gujarat (13 per cent) had the highest inter-caste marriage rates, while Madhya Pradesh (1 per cent), Himachal Pradesh, Chhattisgarh and Goa (2 per cent each) and Punjab (3 per cent) had the lowest. Another survey, conducted by the Lok Foundation and CMIE, shows that while south Indian states have higher inter-caste marriage rates compared to the national average, Tamil Nadu stands out with only 3 per cent.


Also read: More than husbands, educate moms-in-law if you want to change arranged marriages in India


But there is some good news. The Lok Foundation survey reveals that more Indians are accepting inter-caste marriages for their children. Interestingly, of all factors, women with more years of education tend to be more accepting of inter-caste marriages for their children. So if you are thinking of marrying someone outside your caste, your chances improve if your would-be mother-in-law is educated.

(Disclosure: A member of my immediate family works for a company that provides genetic testing services)

The author is the director of the Takshashila Institution, an independent centre for research and education in public policy.

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3 COMMENTS

  1. It has both pros and cons..to simplify main affect: reduction in rare disorder as well as complex disorder load we are seeing presently…cons: appearance of newer and unique, altogether absent rare disorders (especially recessive traits), that remained restricted so far due to structure and isolation due to initial settlements and then conserved population structure…so not that simply straightforward..

  2. I am a big fan of Nitin Pai.
    His articles are always brain churning and elicit thoughts away from the routine.
    In India we have been marrying inter-caste since time immemorial.
    The “Gandharva Vivaha” was quite common all over India.
    You find its mention even in Upanishadas.
    The most famous example being that of Shakuntala marrying Dushyanta.
    The marriage has been eulogised in Mahabharata as well as in Abhijñānashākuntala.
    Shakuntala, parentage unknown, grew up as a Brahmin and married the King, a Kshatriya.
    They sired Bharata who is ancestor of Pandavas and Kauravas.
    The marriages in India although have been mostly within a caste but never in the same “gotra”.
    The genealogy in India especially for marriages is not based on caste but on “gotra” making sure that genetic problems do not occur in our society in the future.
    Our society has been very conservative when it comes to marrying in the same “gotra” which tells about your ancestors.
    We have been a very scientifically evolved society.
    Do you not find dark skinned North Indians and fair skinned South Indians?
    And mind you these are not exceptions.
    Name any love story of last two thousand years and it would be inter-caste one.
    In Maharashtra many Brahmins have blue eyes. We all know the ancestory.
    Comparison between a handful of Europeans with genetically vastly different millions of Indians needs to be taken with a pinch of salt.

    • Col, you’re appropriating the study in the wrong sense. I mean you’re painting an Hindutuva face and saying, ” See we had it in our Vedas, Scriptures, which are obviously fictional. It is your Vedas, Gita blah blah advocates Vedas. So don’t appropriate for the sake your benefit.

      You say, Indians are marrying within their caste but not within their ‘Gotras’, it is been explicity mentioned in the article the DNA might recur if couples are from same ancestor. Tracing ‘Gotras’ would reveal they are from similar ancestors.

      So, from this study it is evident, Aryans infused their conservative Culture into the Existing Harappans (Dravidians). Times up Col, break your preconceived myths and try to understand the Scientific reality.

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