Genomic analysis reveals geography rather than culture as the predominant factor shaping genetic variation in northern Kenyan human populations

Abstract

20 Objectives: The aim of this study was to characterize the genetic relationships within and among 21 four neighboring populations in northern Kenya in light of cultural relationships to understand the 22 extent to which geography and culture shape patterns of genetic variation. 23 Materials and Methods: We collected DNA and demographic information pertaining to aspects 24 of social identity and heritage from 572 individuals across the Turkana, Samburu, Waso Borana, 25 and Rendille of northern Kenya. We sampled individuals across a total of nine clans from these 26 four groups and, additionally, three territorial sections within the Turkana and successfully 27 genotyped 376 individuals. 28 Results: Here we report that geography predominately shapes genetic variation within and 29 among human groups in northern Kenya. We observed a clinal pattern of genetic variation that 30 mirrors the overall geographic distribution of the individuals we sampled. We also found relatively 31 higher rates of intermarriage between the Rendille and Samburu and evidence of gene flow 32 between them that reflect these higher rates of intermarriage. Among the Turkana, we observed 33 strong recent genetic substructuring based on territorial section affiliation. Within ethnolinguistic 34 groups, we found that Y chromosome haplotypes do not consistently cluster by natal clan 35 affiliation. Finally, we found that sampled populations that are geographically closer have lower 36 genetic differentiation, and that cultural similarity does not predict genetic similarity as a whole 37 across these northern Kenyan populations. 38 Discussion: Overall, the results from this study highlight the importance of geography, even on 39 a local geographic scale, in shaping observed patterns of genetic variation in human populations. 40 Keywords 41 Africa, Kenya, geography, culture, social organization, genetic structure, genetic FST, cultural FST 2 bioRxiv preprint doi: https://doi.org/10.1101/2021.10.29.466304; this version posted November 1, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license. 42