Y-chromosomal microsatellites and expansion from Africa

Abstract

AbstractSome diversities are thought to mark human expansion from Africa – they decline as distance from Africa accumulates, and suggest that the expansion originated from any of a range of locations which are only in Africa. Previously, a decline was found regarding Y-chromosomal microsatellite heterozygosity. However, this diversity has been noted to suggest a non-African starting point and, consequently, not appearing reflective of expansion from Africa. Declines have appeared in other variables derived through Y-chromosomal microsatellites, including effective population size, expansion time, and time to the most recent common ancestor. The present research inferred if these variables, and some Y-chromosomal diversities, indicate expansion from Africa; indicative variables could help with identifying which area of Africa the expansion started in. This research used variables derived previously from Y-chromosomal microsatellites for populations worldwide (effective population size, expansion time, and time to the most recent common ancestor) or only in Africa (haplotype and repeat unit diversities). Regarding populations worldwide, San were very high in each variable when considering distance from (southern) Africa. Without San, effective population size and time to the most recent common ancestor did not squarely indicate an African origin, and expansion time placed the origin wholly outside of Africa. When using San, each area was only in Africa. Amongst African populations, whilst both haplotype diversity and repeat unit diversity showed a geographical pattern of declining, only haplotype diversity suggested a completely African area of origin. Using Y-chromosomal haplotype diversity alongside some other genetic diversities, a southern African origin was broadly indicated.