Is violence necessary to explain the post-Neolithic Y chromosome bottleneck?
Résumé
By analyzing mitochondrial and Y chromosome genetic data in more than 300 current human populations from all over the world, Karmin et al. (Karmin et al., 2015) highlighted that the effective size of Y chromosome underwent a severe bottleneck around 5,000 years ago. This remarkable decrease was not observed for mitochondrial DNA (mtDNA). Similar patterns have later been revealed within European and Near-Eastern populations (Batini et al, 2015, 2017). In 2018, Zeng et al. interpreted this Y chromosome bottleneck as the result of violent intergroup competition between patrilineal descent groups. Indeed, because patrilineal descent groups are made up of closely related men on the paternal line, the Y chromosome is expected to be very homogeneous within a descent group and differentiated between two descent groups. The massacre of some
groups by other groups would then produce a major decrease of Y chromosome diversity within the population. But is violence necessary to explain this past Y chromosome bottleneck ? By simulating populations structured in patrilineal descent groups, we compared the evolution of diversity on the Y chromosome and mtDNA over time for two scenarios: one involving violent competition between descent groups, and the other involving no violent competition. Results suggest that if violent competition between descent groups strongly decreases diversity on the Y chromosome, patrilineality alone is able to trigger a major bottleneck on the Y chromosome with respect to mtDNA.
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