Biology subjects

Myrick, J. W.

Publications and source records attributed to Myrick, J. W..

3 recordsLinked to original sources

bioRxiv2025

Recovering the pre-colonial population structure of Khoe-San descendant populations

San populations from Botswana and Namibia retain exceptional linguistic, cultural and genetic diversity, but few Khoisan-speaking groups remain south of the Kalahari Desert. However, historically, far southern Africa was home to many San and Khoekhoe groups. Popular opinion often implies that such populations do not contribute to the ancestry of contemporary South Africans. Here, we characterize the genetic ancestry of self-identified South African Coloured groups and reconstruct pre- and colonial population structure from 620 newly sampled individuals. These groups retain majority Khoe-San genetic ancestry (>48%), suggesting the persistence of Khoe-San ancestry to the present day. By isolating the Khoe-San ancestry component, we show that it is intermediate between the =Khomani San and Nama, and distinct from Kalahari Khoe-San populations. We also find that signatures of the Indian Ocean slave trade can be traced to Indonesian islands such as Sulawesi, Java, and Flores, while the South Asian ancestry is regionally non-specific. TeaserLarge-scale genomic study uncovers enduring indigenous ancestry in South African populations, exposing a complex past.

evolutionary biology↗

bioRxiv2023

Slave Trade and Colonial Expansion Resulted in Strong Sex-Biased Admixture in South Africa

The colonial-period arrival of Europeans in southern Africa is associated with strong sex-biased migration by which male settlers displaced indigenous Khoekhoe and San men. Simultaneously, the importation of South Asian, Indonesian and Eastern African slaves may have contributed female-biased migration to Cape Town and surrounding areas. We examine the spatial and temporal spread of sex-biased migration from the Cape northward into Namaqualand and the southern Kalahari using genetic data from more than 1,400 individuals. In all regions, admixture patterns were sex-biased, with evidence of a greater male contribution of European ancestry and greater female contribution of Khoe-San ancestry. While admixture among Khoe-San, European, equatorial African, and Asian groups has likely been continuous from the founding of Cape Town to present-day, we find that Khoe-San groups further north experienced a single pulse of European admixture 6-8 generations ago. European admixture was followed by additional Khoe-San gene flow, potentially reflecting an aggregation of indigenous groups due to disruption by colonial interlopers. Male migration into the northern frontier territories was not a homogenous group of expanding Afrikaners and slaves. The Nama show evidence of distinct founder effects and derive 15% of their male lineages from Asian men, a pattern absent in the =Khomani San. Khoe-San ancestry from the paternal line is greatly diminished in populations from Cape Town, the Cederberg Mountains and Upington, but remains more frequent in self-identified ethnically indigenous groups. Strikingly, we estimate that Khoe-San Y-chromosomes were experiencing unprecedented population growth at the time of European arrival. Our findings shed light on the patterns of admixture and the population history of South Africa as the colonial frontier expanded.

genetics↗

bioRxiv2017

An Unexpectedly Complex Architecture for Skin Pigmentation in Africans

Fewer than 15 genes have been directly associated with skin pigmentation variation in humans, leading to its characterization as a relatively simple trait. However, by assembling a global survey of quantitative skin pigmentation phenotypes, we demonstrate that pigmentation is more complex than previously assumed with genetic architecture varying by latitude. We investigate polygenicity in the Khoe and the San, populations indigenous to southern Africa, who have considerably lighter skin than equatorial Africans. We demonstrate that skin pigmentation is highly heritable, but that known pigmentation loci explain only a small fraction of the variance. Rather, baseline skin pigmentation is a complex, polygenic trait in the KhoeSan. Despite this, we identify canonical and non-canonical skin pigmentation loci, including near SLC24A5, TYRP1, SMARCA2/VLDLR, and SNX13 using a genome-wide association approach complemented by targeted resequencing. By considering diverse, under-studied African populations, we show how the architecture of skin pigmentation can vary across humans subject to different local evolutionary pressures.\n\nHighlightsO_LISkin pigmentation in Africans is far more polygenic than light skin pigmentation in Eurasians.\nC_LIO_LIKhoeSan[§] populations, which diverged early in human prehistory from other populations, have lightened skin pigmentation compared to equatorial Africans.\nC_LIO_LISkin color is highly heritable in the KhoeSan, but pigmentation variability is not well explained by previously discovered pigmentation genes.\nC_LIO_LIWe perform the first GWAS for pigmentation in African KhoeSan populations and identify canonical pigmentation loci near TYRP1 and in SLC24A5, as well as novel associations surrounding SMARCA2 and other genes.\nC_LI

genetics↗