GENETIC-VARIATION IN INDIA

In the last 25 years a number of genetic studies on the populations of the Indian subcontinent have been conducted. Unfortunately, most of t he studies covered a limited number of genetic systems, and only a few provide information on the genetic differentiation and population str ucture of some regional caste, tribal, religious, and urban groups. De spite a recent report suggesting that in eastern India genetic affinit y does not show any large degree of congruence with sociocultural hier archy, three distinct surveys reported here indicate that geographic p roximity, ethnohistory, and biosocial and cultural affiliation are imp ortant determinants of genetic affinity. Gene differentiation studies are few, but from the information of some previous papers and results presented in this special issue of Human Biology, the pattern of diffe rentiation is becoming clear. In general, genetic differentiation in p opulations of India is low (0.26-1.7%), but overall genetic differenti ation in 18 mixed populations of India is higher (2.23%), similar to t he largest single study on 16 tribal groups from central India (2.18%) . The tribal population of South India shows the highest F-ST value (4 .1%), and this value is similar to a study of the Dhangar caste group. The reason for this high F-ST value is not clear. One possibility may be (semi-) isolation associated with such factors as random inbreedin g and drift, which can cause high levels of genetic differentiation am ong the tribal groups of India and among the castes such as Dhangar. H owever, further studies are needed to explore the causes of such high values of genetic differentiation, especially in these populations.