Genetic affinities and sub-structuring in Coorg population of Southern India

The Coorgs, also known as Kodavas, are one of the smallest religious and socio-culturally homogenous communities in the world, currently residing in the state of Karnataka, India. Due to a stark contrast with the surrounding subpopulations, their genetic architecture and population & demographic history have been a matter of debate for long. To better understand the population structure and demographic history of this caste group, we analysed the population, using high-resolution autosomal (n=70) as well uniparentally inherited markers (Y-chromosomal and mitochondrial DNA) (n=144). Our first ever findings elucidate that origin of Coorgs traces back to early or middle Bronze Age. We further found population substructure among Coorgs, which manifested as three distinct clusters in a Principal component analysis. One of these subgroups has undergone a rare and immense amount of population-specific drift but all three eventually admixed, both genetically and socio-culturally. The mtDNA analysis showed 40% South Asian-specific mitochondrial lineages among Coorgs; while the Y-chromosomal analysis revealed predominant presence of Eurasian, Middle-Eastern and Indian-specific haplogroups suggesting male-centric migration and eventual assimilation with local females. Our results for the first time identify these ancient and distinct genealogies that make up the contemporary Coorgs and may explain the socio-cultural differences with their immediate and distant neighbours in the country and the prevalent narrative history. In a wider context, the study also reveals an ancient, yet unknown, Middle Eastern source population that might have contributed to an early west to east migration into India.