Differential Reproduction

[JesusA (imported)]

There has been discussion (especially in the popular literature) about the discrepancy in estimated time since humans' most recent female common ancestor and male common ancestor. The female common ancestor (Mitochondrial Eve) is estimated to have lived somewhere between 171 and 238 thousand years ago (frequently stated as 200 thousand) and the male common ancestor (Y Chromosome Adam) as having lived between 46 and 109 thousand years ago (frequently stated as 100 thousand). How to account for the discrepancy?

Three biologists did a complex analysis using large samples from three very different populations: Khoisan Bushmen from South Africa, Mongolians, and Papua New Guineans. Their results demonstrate differential reproduction rates for males and females.

In rough terms, over the course of human history, about 80% of females have left descendants who have survived to reproduce, while only about 40% of males have. Their conclusion was that humans are basically polygamous and that over the broad sweep of human history a majority of males were excluded from reproduction.

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Wilder, JA, Mobasher, Z, & Hammer, MF. (2004). Genetic Evidence for Unequal Effective Population Sizes Human Females and Males. Molecular Biology and Evolution, vol. 21, no. 11, pp. 2047-2057.