The derived EDAR allele

A derived G-allele point mutation (SNP) with pleiotropic effects in EDAR, 370A or rs3827760, is found in ancient and modern East Asians, North Asians, Southeast Asians, Nepalese,^[5] and Native Americans but not common in African or European populations.

Experimental research in mice has linked the derived allele to a number of traits, including greater hair shaft diameter, more numerous sweat glands, smaller mammary fat pad, and increased mammary gland density.^[6] A 2008 study stated that EDAR is a genetic determinant for hair thickness, and also contributed to variations in hair thickness among Asian populations.^[7] Derived variants of EDAR are associated with multiple facial and dental characteristics, such as shovel-shaped incisors.^{[8][9][10][11]} This mutation is also implicated in ear morphology differences and reduced chin protrusion.^[12]

A 2013 study suggested that the EDAR variant (370A) arose about 35,000 years ago in central China, a period during which the region was then quite warm and humid.^[13] A subsequent study from 2021, based on ancient DNA samples, has suggested that the derived variant became dominant among Ancient Northern East Asians shortly after the Last Glacial Maximum in Northeast Asia, around 19,000 years ago. Ancient remains from Northern East Asia, such as the Tianyuan Man (40,000 years old) and the AR33K (33,000 years old) specimen lacked the derived EDAR allele, while ancient East Asian remains after the LGM carry the derived EDAR allele.^[14][15]

It has been hypothesized that natural selection favored this allele during the last ice age in a population of people living in isolation in Beringia, as it may play a role in the synthesis of Vitamin D-rich breast milk in dark environments.^[16][17][18] One study suggested that because the EDAR mutation arose in a cool and dry environment, it may have been adaptive by increasing skin lubrication, thus reducing dryness in exposed facial structures.^[19]

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Besides being interesting in itself, this allele explains why East, North and Southeast Asian females typically have small breasts. ABN