Investigating the demographic history of Sindhi population inhabited in West Coast India.

Background: South Asian populations are genetically well stratified due to multiple waves of migration, admixture events, and endogamy. India remains a rich resource for population genomics studies with many small and socio-culturally homogeneous communities whose origins and demographic histories are largely unknown.

Methods: In this study, we analysed such a small Sindhi settlement in the Thane district in Maharashtra of West coast India using genome-wide autosomal SNP data from 13 healthy Sindhi individuals using both frequency- and haplotype-based approaches.

Results: Our analyses suggest that the West coast Indian Sindhi community is very unique and has significant population affinity with a group more closely related to the Pakistani Burusho than to the Pakistani Sindhi, as it has an additional East/Southeast Asian component. Furthermore, the sharing of haplotypes and Identity by Descent (IBD) suggests recent gene flow from the local Konkani population on the west coast of India into Indian Sindhi. Admixture modelling suggested that Indian Sindhi admixture with the East/Southeast Asian source group could be 40-50 generations before present (GBP), explaining their current unique demographics. However, apart from this additional admixture, they share the basic genetic composition of the Pakistan/Northwest Indian groups, as reflected in Principal Component Analysis (PCA), outgroup F3 and IBD sharing.

Conclusion: Our new findings suggest that Indian Sindhi settlement from the Thane in Maharashtra in West coast of India derive their genetic ancestry not directly from Pakistani Sindhis but from other groups related to Burusho in Pakistan. The study therefore encourages further research to identify the heterogeneous nature of migrations to the Indian subcontinent and thus further decipher its unique demographics.