No abstract

Skin pigmentation is one of the most variable phenotypic traits in humans. A non-synonymous substitution (rs1426654) in the third exon of SLC24A5 accounts for lighter skin in Europeans but not in East Asians. A previous genome-wide association study carried out in a heterogeneous sample of UK immigrants of South Asian descent suggested that this gene also contributes significantly to skin pigmentation variation among South Asians. In the present study, we have quantitatively assessed skin pigmentation for a largely homogeneous cohort of 1228 individuals from the Southern region of the Indian subcontinent. Our data confirm significant association of rs1426654 SNP with skin pigmentation, explaining about 27% of total phenotypic variation in the cohort studied. Our extensive survey of the polymorphism in 1573 individuals from 54 ethnic populations across the Indian subcontinent reveals wide presence of the derived-A allele, although the frequencies vary substantially among populations. We also show that the geospatial pattern of this allele is complex, but most importantly, reflects strong influence of language, geography and demographic history of the populations. Sequencing 11.74 kb of SLC24A5 in 95 individuals worldwide reveals that the rs1426654-A alleles in South Asian and West Eurasian populations are monophyletic and occur on the background of a common haplotype that is characterized by low genetic diversity. We date the coalescence of the light skin associated allele at 22–28 KYA. Both our sequence and genome-wide genotype data confirm that this gene has been a target for positive selection among Europeans. However, the latter also shows additional evidence of selection in populations of the Middle East, Central Asia, Pakistan and North India but not in South India.

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.

The Indian cheetah was hunted to extinction by the mid-20th century. While analysis of 139 bp of mitochondrial DNA (mtDNA) has confirmed that the Indian cheetah was part of the Asiatic subspecies (Acinonyx jubatus venaticus), the detailed relationships between cheetah populations remains unclear due to limited genetic data. We clarify these relationships by studying larger fragments of cheetah mtDNA, both from an Indian cheetah museum specimen and two African cheetah, one modern and one historic, imported into India at different times. Our results suggest that the most recent common ancestor of cheetah mtDnA is approximately twice as ancient as currently recognised. the indian and Southeast African (Acinonyx jubatus jubatus) cheetah mtDNA diverged approximately 72 kya, while the Southeast and northeast African (Acinonyx jubatus soemmeringii) cheetah mtDnA diverged around 139 kya. Additionally, the historic African cheetah sampled from India proved to have an A. j. jubatus haplotype, suggesting a hitherto unrecognised South African route of cheetah importation into India in the 19 th century. Together, our results provide a deeper understanding of the relationships between cheetah subspecies, and have important implications for the conservation of A. j. venaticus and potential reintroduction of cheetahs into india.

Objectives: Skin color is a classic example of a visible human trait that varies widely among and between human populations; it has evolved finely balancing photoprotection and 25(OH)D (vitamin D) synthesis as opposing selection forces. While the health effects of vitamin D deficiency in Northern European populations are profound, we are yet to accurately characterize the evolutionary relationship between vitamin D requirements and skin color diversity. Materials and Methods: This study explored this relation among a cohort of 170 children from central Poland considering season of measurement and socioeconomic status (SES). Alongside completed questionnaires, saliva was collected and the level of 25(OH)D was assessed using an enzyme-linked immunosorbent assay kit; furthermore, a Dermaspectrometer was used to measure skin color by recording the Melanin Index (MI). Results: First, 25(OH)D concentration or skin color variation are not significantly different between boys and girls; second, 25(OH)D concentration is lower in late autumn than in spring, while skin color (MI) is darker in autumn; crucially, we found significant association between MI and 25(OH)D concentration: higher MI is significantly associated with lower 25(OH)D levels only in boys measured in autumn, and not in spring. Conclusions: These results shed light on the factors affecting 25(OH)D concentration and MI variation in a cohort of Polish children: they offer an evolutionary perspective on the potential role of vitamin D as a driver of skin color diversity while informing a key public health debate.