Manjari Jonnalagadda1, Shantanu Ozarkar1, Richa Ashma2, Shaunak Kulkarni1. 1. Department of Anthropology, Savitribai Phule Pune University, Pune, 411007, Maharashtra, India. 2. Department of Zoology, Savitribai Phule Pune University, Pune, 411007, Maharashtra, India.
Abstract
OBJECTIVES: Global patterns of skin pigmentation have evolved as an adaptation to local ultraviolet radiation (UVR). Indian populations exposed to intense UVR show great variation in skin pigmentation. The UVR-based selection model cannot satisfactorily address the high prevalence of light skin among these populations. Thus, the present study examines pigmentation variation among populations of West Maharashtra and the Indian subcontinent within the context of population structure and social hierarchy. METHODS: Melanin index (MI) was measured from 555 individuals representing six endogamous populations of West Maharashtra. Skin pigmentation was assessed in terms of variation between populations and differences between and among castes and tribes. A linear regression analysis was run to assess the relationship among MI, UVR, and social hierarchy using published MI data from 13 Indian endogamous populations. RESULTS: Skin pigmentation differed significantly among populations of West Maharashtra. Significant pigmentation variation exists between castes and tribes of West Maharashtra as well as across the Indian subcontinent. We observe a significant negative relationship between social hierarchy and skin pigmentation, whereas the relationship between UVR and MI is weak. CONCLUSIONS: Our results suggest that various factors may have contributed to pigmentation diversity across the Indian subcontinent. The lack of correlation between UVR and MI suggests that natural selection may not have played a significant role in shaping pigmentation variation across the subcontinent. We discuss other possible explanations, including metabolic conservation and cultural factors such as traditional social hierarchies and strict endogamy that have led to the development of population structure.
OBJECTIVES: Global patterns of skin pigmentation have evolved as an adaptation to local ultraviolet radiation (UVR). Indian populations exposed to intense UVR show great variation in skin pigmentation. The UVR-based selection model cannot satisfactorily address the high prevalence of light skin among these populations. Thus, the present study examines pigmentation variation among populations of West Maharashtra and the Indian subcontinent within the context of population structure and social hierarchy. METHODS: Melanin index (MI) was measured from 555 individuals representing six endogamous populations of West Maharashtra. Skin pigmentation was assessed in terms of variation between populations and differences between and among castes and tribes. A linear regression analysis was run to assess the relationship among MI, UVR, and social hierarchy using published MI data from 13 Indian endogamous populations. RESULTS:Skin pigmentation differed significantly among populations of West Maharashtra. Significant pigmentation variation exists between castes and tribes of West Maharashtra as well as across the Indian subcontinent. We observe a significant negative relationship between social hierarchy and skin pigmentation, whereas the relationship between UVR and MI is weak. CONCLUSIONS: Our results suggest that various factors may have contributed to pigmentation diversity across the Indian subcontinent. The lack of correlation between UVR and MI suggests that natural selection may not have played a significant role in shaping pigmentation variation across the subcontinent. We discuss other possible explanations, including metabolic conservation and cultural factors such as traditional social hierarchies and strict endogamy that have led to the development of population structure.
Authors: Nicholas G Crawford; Derek E Kelly; Matthew E B Hansen; Marcia H Beltrame; Shaohua Fan; Shanna L Bowman; Ethan Jewett; Alessia Ranciaro; Simon Thompson; Yancy Lo; Susanne P Pfeifer; Jeffrey D Jensen; Michael C Campbell; William Beggs; Farhad Hormozdiari; Sununguko Wata Mpoloka; Gaonyadiwe George Mokone; Thomas Nyambo; Dawit Wolde Meskel; Gurja Belay; Jake Haut; Harriet Rothschild; Leonard Zon; Yi Zhou; Michael A Kovacs; Mai Xu; Tongwu Zhang; Kevin Bishop; Jason Sinclair; Cecilia Rivas; Eugene Elliot; Jiyeon Choi; Shengchao A Li; Belynda Hicks; Shawn Burgess; Christian Abnet; Dawn E Watkins-Chow; Elena Oceana; Yun S Song; Eleazar Eskin; Kevin M Brown; Michael S Marks; Stacie K Loftus; William J Pavan; Meredith Yeager; Stephen Chanock; Sarah A Tishkoff Journal: Science Date: 2017-10-12 Impact factor: 47.728