The Parallel Lives of Human Y Chromosome Lineages Across the Strait of Gibraltar

The patrilineal transmission of the Y chromosome and the fact that diversity in it accumulates along a strict genealogy imply that, by observing the current Y chromosome diversity in men, inferences can be made about the male-mediated history of humans (exactly like the female-mediated history is traced by mitochondrial DNA). By resequencing the non-recombining portion of the Y chromosome, it has been recently recognized that many branches of the Y chromosome genealogy (the so-called haplogroups) have expanded recently in bursts often tied to lifestyle changes or technological innovations. We have analysed two such bursting haplogroups: R1b-DF27 and E-M183. R1b-DF27 is prevalent in the Iberian Peninsula (40-70%), while its frequency drops to <15% north of the Pyrenees. We have estimated its age at similar to 4000 years ago, in line with ancient DNA discoveries and pointing to the population upheaval of the Bronze Age as a plausible agent in its origin and dispersion. Similarly, across the Strait of Gibraltar, E-M183 (equivalent to E-M81) dominates the Y chromosome landscape in NW Africa (up to 70%) and is much rarer elsewhere. However, its origins are more recent, at similar to 2000 years ago, and more difficult to pin down to a particular historical event. In conclusion, either in Iberia or the Maghreb, most men share a common ancestor that lived just a few hundred generations ago.