But, not cast(e) in stone

Khap or caste panchayats that zealously guard against marriages outside their caste or gotra often claim that such alliances violate age-old social norms. The four-varna caste system, supposedly described in the Vedas and other texts, is often cited to justify marriages within castes or clans.

Sociologists and anthropologists offer reformative solutions like education and improving the status of women in societies practising gotra or caste system. It is time we look inside our DNA — literally so — for deeper understanding of the problem. That’s precisely what Indian scientists have done and found that though the caste system or social classification as it is practiced today has existed for a long time, it has not existed forever.

The study of genetic information frozen in our DNAs is far more important than trivial, headline grabbing applications such as digging lineage of celebs like Prince William as highlighted recently. Mitochondrial DNA, passed from a mother to her children, has emerged as a valuable tool to study human evolution in the past two decades. One inherits it only from the mother and it does not change very much from generation to generation.

This means a person’s mitochondrial DNA is identical to that of his or her direct maternal ancestor dozens of generations ago, and this knowledge is being used to connect people across centuries and continents. In the past one decade, scientists from the Hyderabad-based Centre for Cellular and Molecular Biology (CCMB) along with their international collaborators have used genetic data from diverse population groups to give us an idea of how Indians have evolved.

It seems the first set of modern humans to have migrated to the Indian subcontinent were the Andamanese 65,000 to 75,000 years ago. They then migrated to coastal areas in South India and mixed with Dravidian population groups. Scientists refer to these first inhabitants of India as Ancestral South Indians (ASI). The second wave of migration from Africa took place 40,000 to 45,000 years ago. During migration this group probably split into two — one inhabiting Europe and the other heading towards Middle East and then India.

This group has been dubbed Ancestral North Indians (ANI). This explains why ASIs don’t show any genetic affinity to groups outside the Indian subcontinent and ANIs show 30 to 70 percent genetic affinity to West Asians, Middle Easterners, Europeans and Caucasians. Most Indian population groups descended from a mixture of these two genetically divergent populations — ASI and ANI. This study had major implications for Indian history because it clearly showed that the origin of genetic diversity found in South Asia is much older than 3,500 years when the Indo-Aryans were supposed to have migrated to India. This means, genetically speaking, there was no Aryan invasion at all.

Now CCMB scientists have been able to put a date to admixture between ASI and ANI — crucial for a fuller understanding of Indian history. The admixture, according to findings of the study published by Dr Kumarasamy Thangaraj and colleagues this month, probably took place 1,900 to 4,200 years ago.

The most remarkable aspect of the mixture is its pervasiveness. It affected not just traditionally upper-caste groups, but also traditionally lower-caste and isolated tribal groups such as Bhils or Palliyars, all of whom are united in their history of genetic mixture in the past few thousand years. The time-frame implies that India experienced a demographic transformation during this period —  from being a region in which major population mixture was common to one in which mixture even between closely related groups became rare as reflected in a shift to endogamy (a key attribute of the caste system).

The fact that Indians evolved from randomly mixed groups suggests that social classifications like the caste system did not exist in the same way before the mixture. In other words, the present-day structure of the caste system came into being only relatively recently. But once established, the caste system became genetically effective because mixture across groups became very rare. The Vysya community from Andhra Pradesh, which has experienced negligible gene flow from neighbouring groups for 3,000 years, is an illustrative example of this. Many population groups have evolved in genetic isolation during this period.

It is time we as a society learn from the new evidence emerging from genetic studies. We need to revise our notions about how India evolved in the past few thousand years. The current understanding of pre-history of India is based on Rig Veda which is believed to have been written at different times because earlier parts do not have any specific reference to the caste system. Similarly the notion of an Aryan invasion is based on Max Muller’s linguistic studies implying migration of Indo-European speakers from Central Asia. Genetic data does not support such notions. Historians and sociologists need to look beyond ancient texts and work with geneticists for a clearer understanding of our past.

Besides necessitating revisions in history, genetic studies are of utmost importance for medical research. The high incidence of genetic and population-specific diseases that is characteristic of present-day India is a result of the system of strict endogamous marriages. 

The frequency of genetic mutation increases when people marry within the community. This leads to genetic disorders. Vysyas of Andhra Pradesh who have been marrying within the group for several hundred generations suffer from a typical problem. When anesthesia is administered to any member of the community for surgery, they take much longer than others to come out of it. Some of them could suffer paralysis too.

Similarly, Parsis seem to  have a higher frequency of breast cancer. Several other population groups suffer from genetic disorders. Greater awareness could lead to genetic counselling and options beyond closed communities while marrying.

As regards, caste panchayats the message is clear: celebrate India’s genetic diversity and encourage inter-caste marriages.

The writer is a science journalist and author based in New Delhi