Indian island settlers came from far and wide

People living on Lakshadweep, an archipelago off the south-western coast of India in the Arabian Sea, are genetically closer to people of mainland India, Maldives, Sri Lanka and Pakistan than to populations living elsewhere in the world, research reveals.

The archipelago comprises a cluster of 35 islands, scattered over 78,000 square kilometres with a population of about 65,000. The islands have been stopovers for sailors since ancient times, but it is not clear when they were first permanently settled. 

Because of its geographical location, the present-day populations in Lakshadweep may offer a unique insight into historic migration events. The islanders might have mingled with people from pan-world ethnicity, creating a mosaic-like pattern in their ancestry. 

To shed light on their origins, a team of biologists, led by Kumarasamy Thangaraj from the Centre for Cellular and Molecular Biology in Hyderabad, India, drew blood samples from them. The researchers then sequenced genes to detect specific markers to trace back maternal and paternal lineages.  

  For tracking maternal ancestors, Thangaraj and colleagues scanned mitochondrial DNA (mtDNA), which is only passed from a mother to her children. 

For paternal ancestry, they looked for genetic markers on the male-specific Y chromosome. 

They then compared the markers identified in the island populations with those of neighbouring regions such as India, the Maldives, Sri Lanka and Pakistan. 

In a paper published in the journal Scientific Reports, the researchers report that all the islands show major components of maternal ancestry associated with South Asia. Two of the islands – Kalpeni and Minicoy – have substantial West Eurasian-specific maternal ancestry, which is largely similar to the Maldives and Sri Lanka.

The sharing of many of the maternal lineages among the islands shows a high level of intra-island gene flow. The results indicate that the islanders have a close genetic affinity with the people living in the Indian state of Kerala. 

Paternal affinity results, in contrast, did not favour Kerala at all. Rather, they indicate ancestry stemming from to the Maldives, North India and Pakistan.  

Despite it being a maritime crossroad, a reduced diversity for both maternal and paternal ancestries was observed among the populations on most of the Lakshadweep islands.

The exception was Minicoy, suggesting it has long been a favoured destination for sailors. 

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