Novel insights on demographic history of tribal and caste groups from West Maharashtra (India) using genome-wide data

Guilherme Debortoli,Cesar Fortes-Lima,Francisco Ceballos,Cristina Abbatangelo,Shantanu Ozarkar,Esteban J Parra,Manjari Jonnalagadda,Heather L Norton

doi:10.1038/s41598-020-66953-3

Abstract

The South Asian subcontinent is characterized by a complex history of human migrations and population interactions. In this study, we used genome-wide data to provide novel insights on the demographic history and population relationships of six Indo-European populations from the Indian State of West Maharashtra. The samples correspond to two castes (Deshastha Brahmins and Kunbi Marathas) and four tribal groups (Kokana, Warli, Bhil and Pawara). We show that tribal groups have had much smaller effective population sizes than castes, and that genetic drift has had a higher impact in tribal populations. We also show clear affinities between the Bhil and Pawara tribes, and to a lesser extent, between the Warli and Kokana tribes. Our comparisons with available modern and ancient DNA datasets from South Asia indicate that the Brahmin caste has higher Ancient Iranian and Steppe pastoralist contributions than the Kunbi Marathas caste. Additionally, in contrast to the two castes, tribal groups have very high Ancient Ancestral South Indian (AASI) contributions. Indo-European tribal groups tend to have higher Steppe contributions than Dravidian tribal groups, providing further support for the hypothesis that Steppe pastoralists were the source of Indo-European languages in South Asia, as well as Europe.

Highlights

The South Asian subcontinent is characterized by a complex history of human migrations and interactions, as well as a variety of traditional practices, all of which have contributed to an extensive cultural and genetic diversity
These studies suggest that a distinctive genetic mixture of ancient Iranians and Ancestral South Indian (AASI) could have formed the genetic basis of the Indus Valley Civilization (IVC), this mixture was denoted the “Indus Periphery”
During the decline of the IVC, a portion of the Indus Periphery population admixed with the AASI to form the Ancestral South Indians (ASI) in the Southern regions of India, whereas subsequent interaction between Indus Periphery and incoming Steppe-MLBA populations in the Northern regions resulted in the formation of the ANI5,6

Summary

Introduction

The South Asian subcontinent is characterized by a complex history of human migrations and interactions, as well as a variety of traditional practices, all of which have contributed to an extensive cultural and genetic diversity. To estimate the relative contributions of AASI-related (Andamanese), Indus-Diaspora-related and Steppe-related groups to the WM tribal and caste populations, as well as other relevant groups from South Asia we used the program qpAdm. Supplementary Table 10 provides the estimates of the relative admixture proportions from each source group for each target population.

Results

Conclusion