Caste system: an indigenous invention in South India? Patrilineage and demographic events seem to have brought in social strata and restricted gene pools, not external intervention What is the origin of the caste system in India? This has been a contentious subject in the history of our country. Was this an import from outside? A strong group of scholars think that it was the doing of the people who came from West Asia who migrated and settled here around 3000 â€“ 4000 years ago. This â€˜externalâ€™ or â€˜subjugationâ€™ model has been the received wisdom. On the other hand, there are other scholars who suggest it to be the result of â€œcultural diffusionâ€ among the original inhabitants themselves (anthropologists use the hard-to-pronounce term autochthones, meaning literally sons of the soil, to describe them). Not imported In other words, social hierarchy or stratification is not an imported imposition but an indigenous invention. This alternate model would then posit the caste system to have been with us be much earlier, namely in people who were already in India in the Pleistocene era, between 30,000 â€“ 10,000 years ago. How does one address this question of the origin of the caste system in India? A recent paper by G. Arun Kumar (of the Genographic Laboratory of Madurai Kamaraj University (MKU) Madurai) and others, published in the Journal PLoS ONE on November 28, 2012 (accessible free online at <PLOS ONE 7(11): e50269.doi:10.1371/journal.pone.0050269>) has taken a combination of genetic and anthropological analysis to address this question. And it concludes that social stratification was already present among the Adivasis or tribal groups of Tamil Nadu well before the â€˜Aryanâ€™ migration. In other words, it was and has been an indigenous invention. I asked Professor Ramasamy Pitchappan, the Principal investigator of this project about the details of this study, its methods, results and logic behind the analysis and the conclusions. Prof. Pitchappan was earlier at MKU for long years, and is now at the Chettinad Academy of Research and Education, Chennai. He has been working on the Genographic project for quite some time. He pointed out that they took advantage of two important facts. One is the anthropological fact that the caste system is sustained by patrilineage. In other words, it runs through, and is sustained by the male lineage through generations. The second is the genetic fact that fathers pass on their Y chromosomes in the genome only to their sons, and not to daughters. (Mothers have no such chauvinistic piggery. They pass their X chromosomes both to sons and daughters, plus they pass on their cellular energy factories called mitochondria as well, as matrilineage; no sex-based distinction here). This twin paternal inheritance of restricting the caste designation and the Y chromosome has allowed Pitchappan and collaborators to study over 1,680 people in chosen parts of Tamil Nadu. Many are tribals living in isolation, practicing hunting/gathering, foraging and seasonal dry land agriculture and marrying strictly endogamously within their own sub-tribes (Paliyan, Pulayar, Irulas, Kadar, Thoda, Vanniyar). Analysis of their Y chromosomes across generations, and also of their socio-cultural habits was done by the researchers. This was further compared with non-tribals (for example Brahmins, Sourashtrians, Vadamas, who are thought to be of Indo- European linguistic group). Revealing results The results were revealing. They found strong evidence for genetic structure associated primarily with the mode of subsistence; in other words, fathers passed on their occupation and way of life to their sons. Plus, since the group analyzed specifically one part of the Y chromosome that does not get diluted by recombination, they could do what geneticists refer as coalescence analysis, which allowed them to understand the genetic ancestry of traits and habits. This let them suggest that social stratification of these indigenous sons of the soil had already occurred between 4000 to 6000 years ago, well before the West Asian influx. The authors note that â€œthe overall Y-chromosome patterns, the time depth of population diversifications and the period of differentiation were best explained by the emergence of agricultural technology in South Indiaâ€. In other words, population differentiation occurred well before the â€˜Varnaâ€™ caste system. Patrilineage and demographic events seem to have brought in social strata and restricted gene pools, not external intervention. Chromosomes tell us the genetic history or parentage. Demography tells us how people divided themselves or mixed with one another and brought forth generations. Factors such as climate history, invention and use of tools and technology, and related methods brought people together and made them stay or move in groups. Culture and sociology have isolated and grouped people into stratified societies, restricting them into â€œgene poolsâ€ which is another way of saying â€˜castesâ€™. Finally, look at the irony of it all. After all, mating and marriage is the mixing of genes; the more diverse such mixing, the greater the variety and enrichment of traits. Genetics tells us that the whole world is but one family, a point that the Maha Upanishad furthered by stating ayam bandhurayam neti ganana laghuchetasam udaracharitanam tu vasudhaiva kutumbakam (Only small men discriminate saying: One is a relative; the other is a stranger. For those who live magnanimously the entire world constitutes but a family). Yet, what a caste or any such social pigeonholing does is to restrict this width of choice from an ocean into a gene pool or even a pond!