Y-chromosomal microsatellites and expansion from Africa

Abstract

Research has suggested that Africa is the continent from which modern humans dispersed around the world. Some diversities are thought to trace this expansion; they decline as distance from Africa accumulates, and they suggest that the expansion originated within a range of locations in Africa. Previously, a decline was found regarding Y-chromosomal microsatellite heterozygosity. However, this diversity has been noted to suggest a non-African origin and, consequently, not look like it indicates expansion from Africa. Declines have appeared in other variables which are derived from Y-chromosomal microsatellites. These variables include 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. Variables which indicate the expansion could help with identifying which area of Africa the expansion started in. This research used variables previously derived from Y-chromosomal microsatellites. These variables were for populations from across the world (effective population size, expansion time, and time to the most recent common ancestor) or only in Africa (haplotype and repeat unit diversities). Regarding populations across the world, 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. A southern African origin was broadly indicated when a general estimate of the origin was produced from Y-chromosomal haplotype diversity alongside some other genetic diversities.