Genetic Evolution in South Indian Caste Populations

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Anthropologists have long been interested in the relationship between biology and culture. The Hindu caste system, which established preferred mating practices among the populations of India, is a good example of the impact of social processes on human biology. Numerous investigators have studied the effect of the caste system on genetic variation. Yet the generalizations from this body of work remain unconvincing for several reasons. First, many of the polymorphisms assayed are indirect measurements of DNA variation, are sampled from only a few loci, and are not selectively neutral. Second, many studies do not estimate significance levels or confidence intervals, leaving the findings suspect. Finally, no systematic comparisons have been made with continental populations (i.e., Africans, Asians, and Europeans) using a large, uniform set of DNA polymorphisms. To date, no one has taken advantage of the recent advances in molecular biology to address unresolved questions of long-standing importance to human evolution in India. The proposed research will critically investigate the genetic evolution of South Indian caste populations by (1) formulating and testing hypotheses of the effect of caste subdivision on genetic variation; (2) using a variety of mitochondrial and nuclear DNA polymorphisms; and (3) making direct comparisons to continental populations. The study will analyze mitochondrial DNA, Y-chromosomal DNA, and autosomal DNA polymorphisms with differing rates of mutation from a sample representing individuals in 4 castes spanning the caste hierarchy and 2 tribal populations. Comparisons will be made to our existing data from caste and continental populations.