There’s a new open access paper on human Y chromosome phylogenies, The Y-chromosome tree bursts into leaf: 13,000 high-confidence SNPs covering the majority of known clades, which is just as interesting because of a reference than the paper itself. The paper cited is “Batini, C, P Hallast, D Zadik, et al. submitted. Large-scale recent expansion of European patrilineages shown by population resequencing. Nature Comms.” As I’ve mentioned earlier it was clear from several posters at ASHG that whole genome sequencing of larger sample sizes is making much more clear how recent and rapid the expansion of several of the common lineages across Eurasia was. In particular I’m thinking of R1a and R1b. We know this already from earlier work, but these latest results just confirm it. The truth is visually obviously. Notice in the figure above how R1b fans out in an instant from a single node. This reflects recent rapid population expansion.

But when The Journey of Man and The Seven Daughters of Eve were being written in the early 2000s it was assumed that Y and mtDNA phylogenies could tell us about human prehistory in totality. In hindsight that was probably asking for too much. But because they are sex specific these two lineages can inform us a great deal about social structures. In particular, rapid expansion of Y chromosomal lineages in the recent past may indicate the rise of patriarchy, as powerful males began to see polygyny as a viable strategy due to their monopolization of the resources of whole societies.

If I had to predict, I believe that female lineages tend to be characterized by isolation by distance dynamics. In contrast, male lineages are pruned periodically by rapid expansions and admixtures by groups which are able to marginalize or exterminate competitors over vast swaths of territory. The Genghis Khan effect is just the most prominent of this sort of phenomenon. It is certain that in prehistory this occurred as well, as new technologies such as agricultural triggered social revolutions, and the rise of specialization and stratification among humans.