Unexpected Middle Eastern lineage in South India’s Warrior Clans

ADMIXTURE plot showing Middle Eastern component (Yellow) in the warrior communities

The narrow littoral stretch along the southwestern coast of India is a hotspot of ethnolinguistic diversity. This region, sandwiched between the Arabian Sea and the Western Ghats, is home to several endogamous populations practicing rich traditions and folklore. It is here that two of the world’s major language families, the Indo-European and the Dravidian, have intermingled for centuries. This strategic geographical location has several ancient ports that attracted traders from across the ancient world including the Arabs, Romans, Greeks and the later colonial empires from Europe. The local economy of this region is shaped by tropical landscape, featuring wetland agriculture and vast plantations of arecanut, coconut, and spices. The social structure is complex, including traditionally hunter-gatherers, farmers, artisans and priestly communities.

The south west coast is home to unique warrior communities like the Bunts, Nairs, and Thiyyas, who are particularly known for their matrilineal inheritance practices. Historical accounts have often traced their origins to migrations from North India, Sri Lanka, and beyond. However, the genetic landscape of these groups remained a mystery, until a group of Indian researchers led by Dr. K Thangaraj conducted a detailed study which is now published in Genome Biology and Evolution (Kumar et al. 2023). Their findings unraveled a complex yet distinct genetic makeup of these warrior communities.

The study, which used genome-wide autosomal and uniparental analysis, revealed that these communities form a distinct genetic cluster with significant Middle Eastern ancestry. This discovery challenges the simple Ancient North Indian (ANI) and Ancient South Indian (ASI) dichotomy previously used to explain Indian population genetics (Reich et al. 2009). The clustering analysis placed the five study populations - Nair, Thiyya, Bunt, Ezhava, and Hoysala - genetically between Indo-European and Dravidian speaking groups. Among these, the Nair and Hoysala showed the closest affinity to Gangetic Brahmins, indicating stronger historical connections with northern groups. Meanwhile, the Ezhava group clustered with the Dravidian groups. Remarkably, Thiyya community showed internal diversity, with some individuals clustered among the Nairs and others among the Dravidian groups, suggesting historical stratification within the community.

It was in the model based ADMIXTURE analysis that the distinct Middle Eastern component became observed in the warrior communities and in some Northwest Indian groups. Crucially, this component was entirely absent in the Indo-European speaking populations of the Gangetic plain and the Dravidian speaking tribes. Nairs exhibited this component most prominently, further supporting a north-south migration pattern for this group. The researchers identified that this middle eastern component has its roots in Arabia, is present in modern Iranians, and appears to have flowed into the northwestern India before moving south, strongly hinting at its spread in prehistoric time-depth. The study found no genetic evidence to support the historical claims of Scythian origin for these groups.

To trace how these groups arrived in the south, migration surface analysis using geographical coordinates and pairwise genetic distance was conducted. The results showed that Central India and Godavari and Narmada river basins were crucial migration routes followed by their ancestors. The presence of about 60% ‘Indus Periphery’ ancestry among Bunt and Nairs, a level similar to that found in Kamboj, Gujjar and other northwestern groups, indicates that they all likely belonged to an ancestral population related the Harappans (Indus Valley Civilisation). The study suggests that Bunts and Nairs are likely the descendants of groups that migrated southward after the demise of this civilization. The study does not mention the exact time of divergence, which remains an important question for future research.

Mitochondrial DNA analysis shows high frequencies of West Eurasian haplogroups among Bunts and Thiyyas. This indicates a female-mediated gene flow, which presents a contrasting pattern to the more male-dominated steppe ancestry seen elsewhere in India. Adding another layer to the story, this study also found that these south west coast populations exhibit positive selection in immunity-related genes, those responsible for immune response and viral defence, likely an adaptation to historical disease pressures.

In summary, the findings of this study fundamentally reshape our understanding of South India’s population history by contradicting the simple north-south genetic divide. It also shows how advanced genetic tools can illuminate the complex patterns of admixture and demographic dynamics that have shaped the Indian subcontinent.

References:

Kumar L et al. 2023. Genetic Affinities and Adaptation of the South-West Coast Populations of India. Genome Biol Evol. 15:evad225. doi: 10.1093/gbe/evad225.

Reich D, Thangaraj K, Patterson N, Price AL, Singh L. 2009. Reconstructing Indian population history. Nature. 461:489–494. doi: 10.1038/nature08365.