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Am J Hum Biol. 2018 Sep;30(5):e23170. doi: 10.1002/ajhb.23170. Epub 2018 Aug 12.

The influences of genes, the environment, and social factors on the evolution of skin color diversity in India.

Author information

1
Department of Zoology, University of Cambridge, Cambridge, United Kingdom.
2
Centro de Estudios Interculturales e Indígenas - CIIR, P. Universidad Católica de Chile, Santiago, Chile.
3
Department of Anthropology, The Pennsylvania State University, University Park, State Park, Pennsylvania.
4
CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
5
Birbal Sahni Institute of Palaeosciences, Lucknow, India.
6
Complexity Institute, Nanyang Technological University, Singapore.
7
Estonian Biocentre, Tartu, Estonia.
8
The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom.

Abstract

OBJECTIVES:

Skin color is a highly visible and variable trait across human populations. It is not yet clear how evolutionary forces interact to generate phenotypic diversity. Here, we sought to unravel through an integrative framework the role played by three factors-demography and migration, sexual selection, and natural selection-in driving skin color diversity in India.

METHODS:

Skin reflectance data were collected from 10 diverse socio-cultural populations along the latitudinal expanse of India, including both sexes. We first looked at how skin color varies within and between these populations. Second, we compared patterns of sexual dimorphism in skin color. Third, we studied the influence of ultraviolet radiation on skin color throughout India. Finally, we attempted to disentangle the interactions between these factors in the context of available genetic data.

RESULTS:

We found that the relative importance of these forces varied between populations. Social factors and population structure have played a stronger role than natural selection in shaping skin color diversity across India. Phenotypic overprinting resulted from additional genetic mutations overriding the skin lightening effect of variants such as the SLC24A5 rs1426654-A allele in some populations, in the context of the variable influence of sexual selection. Furthermore, specific genotypes are not associated reliably with specific skin color phenotypes. This result has relevance for DNA forensics and ancient DNA research.

CONCLUSIONS:

India is a crucible of macro- and micro-evolutionary forces, and the complex interactions of physical and social forces are visible in the patterns of skin color seen today in the country.

PMID:
30099804
DOI:
10.1002/ajhb.23170

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