Biology subjects

Sequeira, J. J.

Publications and source records attributed to Sequeira, J. J..

3 recordsLinked to original sources

bioRxiv2024

Maternal genetic affinities of Konkani population in the southwest coast of India

Ko[n]kan region on the west coast of India is a hotspot of culture, folklore and ethnolinguistic diversity. The genetic landscape of this region remains understudied. The present study features Ko[n]kan[i] population residing along the Ko[n]kan Malabar coast. We have sequenced complete mitogenomes of 85 and the hypervariable region of 210 Ko[n]kan[i] individuals to understand the maternal gene pool of this region. Comparative analysis of the over 5000 mitogenomes revealed that the Ko[n]kan[i] population clustered at a convergence point on the PCA plot, presumably due to a diverse maternal gene pool with both autochthonous and West Eurasian components. A distinct clustering pattern was observed within the subgroups of S[a]rasvata and non-S[a]rasvata Ko[n]kan[i] groups, indicating unique ancestral maternal lineages in them. This distinction is majorly due to the N macrohaplogroup lineages found in this population. We observe low haplotype and nucleotide diversity in Citrapur S[a]rasvata Brahmins (CSB), R[a]j[a]pur S[a]rasvata Brahmins (RSB), Kh[a]rvi and Kudubi compared to Gauda S[a]rasvata Brahmins (GSB) and Roman Catholics. The assimilation of both pre and post Last Glacial Maximum (LGM) haplogroups like M57, M36, M37, M3, M30, R8 and U2 in the Ko[n]kan[i] population suggests active movement and settlement along the Ko[n]kan region on the west coast of India since the Late Pleistocene through the Holocene.

genetics↗

bioRxiv2024

Y chromosome STR variation reveals traditional occupation based population structure in India

Earlier models of grouping Indian populations were based on language families, social stratification and geographical location. Such grouping system has often resulted in oversimplification of ancestry inferences. Moreover, we do not find many studies focused on studying the variation within these groups and the role of past demographic events in shaping them. We analysed the Y-chromosome Short Tandem Repeats haplotypes from 8153 males from India and Eurasia to explore the impact of Holocene migration on the Indian gene pool. We used haplotype variation and date estimates to understand the characteristics of each haplogroup with respect to the different grouping models. Our findings show that the Neolithic agricultural expansion has had a strong influence in shaping the male gene pool of the Indian subcontinent. Haplogroups F, L and R1a contribute greatly towards stratifying Indian populations as hunter-gatherer related, farming-related and priestly groups respectively. Although the caste system enforced endogamy, a traditional occupation based admixture existed since the Neolithic times. Dispersal of haplogroup L from the Near East played a major role in the formation of an agriculturist population that formed an intermediary between the primitive tribes and the R1a-rich priestly group. This study shows that the frequency of R1a in the hunter-gatherer tribes (1.5%) is much lower than previously reported based on other models of population clustering.

genetics↗

bioRxiv2024

Novel 4,400-year-old ancestral component in a tribe speaking a Dravidian language

Research has shown that the present-day population on the Indian subcontinent derives its ancestry from at least three components identified with pre-Indo-Iranian agriculturalists once inhabiting the Iranian plateau, pastoralists originating from the Pontic-Caspian steppe and ancient hunter-gatherer related to the Andamanese Islanders. The present-day Indian gene pool represents a gradient of mixtures from these three sources. However, with more sequences of ancient and modern genomes and fine structure analyses, we can expect a more complex picture of ancestry to emerge. In this study, we focus on Dravidian linguistic groups to propose a fourth putative source which may have branched out from the basal Middle Eastern component that gave rise to the Iranian plateau farmer related ancestry. The Elamo-Dravidian theory and the linguistic phylogeny of the Dravidian family tree provide chronological fits for the genetic findings presented here. Our findings show a correlation between the linguistic and genetic lineages in language communities speaking Dravidian languages when they are modelled together. We suggest that this source, which we shall call Proto-Dravidian ancestry, emerged around the dawn of the Indus Valley civilisation. This ancestry is distinct from all other sources described so far, and its plausible origin not later than 4,400 years ago on the region between the Iranian plateau and the Indus valley supports a Dravidian heartland before the arrival of Indo-European languages on the Indian subcontinent. Admixture analysis shows that this Proto-Dravidian ancestry is still carried by most modern inhabitants of the Indian subcontinent other than the tribal populations. This momentous finding underscores the importance of population-specific fine structure studies. We also recommend informed sampling strategies for biobanks and to avoid oversimplification of ancestral reconstruction. Achieving this requires interdisciplinary collaboration.

evolutionary biology↗