A wide spectrum of genetic diversity in mongoloids of India is well documented. Though all mongoloids of India are known to have originated from the Mongol region of China but the period and route of migration from their native land to different Himalayan regions is little known. Thus the studies on genomic diversity of people of Sikkim, a central Himalayan state of India with different migrant mongoloid groups, assume great significance in understanding the impact of migratory events in the genetic differentiation of populations. We therefore studied the genetic diversity on the basis of 13-tetra nucleotide and 2 penta nucleotide microsatellite loci for a total of 208 allele frequencies in three major populations of Sikkim, with different ethno history and time of settlement.
The study on microsatellite allele frequency data suggests that all the three populations of Sikkim are genetically more akin to the mongoloids of China and distinctly apart from the mongoloids of Northeast India. However Sikkim populations are also genetically close to non-mongoloids of surrounding areas. The average heterozygosity and coefficient of gene differentiation among Sikkim populations are moderate. Number of shared alleles and their frequencies, time of divergence and bottleneck effect reveal a distinctiveness of the mongoloids settled in Sikkim from the main Indian mongoloid stock as also different route of migration than the mongoloid population of Northeast India.
Our study clearly demonstrates that the present day mongoloids of Sikkim are genetically distinct from mongoloids of Northeast India due to their different route of migration, time of settlement, and admixture with other non-mongoloid populations of adjoining areas. This substantiates that migratory events have played a significant role in the differentiation of mongoloids of India.