SOCIOBIOLOGY AND HLA GENETIC-POLYMORPHISM IN HILL TRIBES, THE IRULA OF THE NILGIRI HILLS AND THE MALAYALI OF THE SHEVROY HILLS, SOUTH-INDIA

Two endogamous tribes of Tamil Nadu, South India, the Irula of the Nil giri hills and the Malayali of the Shevroy hills, were studied for the ir sociobiology and HLA polymorphism. For sociobiological studies 166 marriages in the Irula and 368 marriages in the Malayali were recorded . The number and spatial distribution of patrilineal clans and their m arriageable range (number of clans from which the brides came) were st udied. Eight clans in the Irula and 16 clans in the Malayali were iden tified. Of these the Kuppar of the Irula and the Malayan of Malayali w ere the largest clans, and both of them had the greatest marriageable range. The numerical strength and the resultant spatial distribution c orrelated well with the marriageable range. HLA-A, B, and DR polymorph ism was studied on 191 Irula and 42 Malayali following standard proced ures. HLA typing revealed high frequencies (>10%) of alleles HLA-AZ, A 9, A11, B17, B35, B40, DR2, and DR7 in both tribes, but the Irula had elevated HLA-A10, B8, and DR8 frequencies and the Malayali had elevate d HLA-A31, B7, DR4, and DR5 frequencies. Two-locus haplotypes A10-B8 a nd A2-B5 were identified in both tribes, but A11-B40 and A2-B53 were p resent only in the Irula and A33-B44 and B15-DR6 were present only in the Malayali. The sociobiology of the Irula was correlated to the HLA genetic profile. The Irula sample was stratified based on dan and HLA data; The Kuppar dan was closer to the Kalkatti, the second largest da n, than to the Pungar and the Sambar clans. Thus the numerical strengt h and spatial distribution of various exogamous clans, presumably a re sult of migration during different periods of history, is reflected in the marriageable range and thus in the genetic distance. In studying HLA or any other genetic polymorphism of an endogamous tribe or caste, one needs to consider the social structure, spatial distribution, and marriageable range.