Genetic study on 'southern route'

[Guest guest]

Am. J. Hum. Genet., 72:000, 2003

 

The Genetic Heritage of the Earliest Settlers Persists Both in

Indian Tribal and Caste Populations

 

T. Kivisild,1,7 S. Rootsi,1 M. Metspalu,1 S. Mastana,2 K. Kaldma,1

J. Parik,1 E. Metspalu,1 M. Adojaan,1 H.-V. Tolk,1 V. Stepanov,3 M.

Gölge,4 E. Usanga,5 S. S. Papiha,6 C. Cinniolu,7 R. King,7 L.

Cavalli-Sforza,7 P. A. Underhill,7 and R. Villems1

 

Two tribal groups from southern Indiathe Chenchus and Koyaswere

analyzed for variation in mitochondrial DNA (mtDNA), the Y

chromosome, and one autosomal locus and were compared with six caste

groups from different parts of India, as well as with western and

central Asians. In mtDNA phylogenetic analyses, the Chenchus and

Koyas coalesce at Indian-specific branches of haplogroups M and N

that cover populations of different social rank from all over the

subcontinent. Coalescence times suggest early late Pleistocene

settlement of southern Asia and suggest that there has not been

total replacement of these settlers by later migrations. H, L, and

R2 are the major Indian Y-chromosomal haplogroups that occur both in

castes and in tribal populations and are rarely found outside the

subcontinent. Haplogroup R1a, previously associated with the

putative Indo-Aryan invasion, was found at its highest frequency in

Punjab but also at a relatively high frequency (26%) in the Chenchu

tribe. This finding, together with the higher R1a-associated short

tandem repeat diversity in India and Iran compared with Europe and

central Asia, suggests that southern and western Asia might be the

source of this haplogroup. Haplotype frequencies of the MX1 locus of

chromosome 21 distinguish Koyas and Chenchus, along with Indian

caste groups, from European and eastern Asian populations. Taken

together, these results show that Indian tribal and caste

populations derive largely from the same genetic heritage of

Pleistocene southern and western Asians and have received limited

gene flow from external regions since the Holocene. The

phylogeography of the primal mtDNA and Y-chromosome founders

suggests that these southern Asian Pleistocene coastal settlers from

Africa would have provided the inocula for the subsequent

differentiation of the distinctive eastern and western Eurasian gene

pools.