The rise of patrilineages

The_Journey_of_Man_-_A_Genetic_OdysseyBeing part of a patrilineage is a big deal today. Ask anyone who is a Cohen, or claims to be a Sayyid, or a descendant of Confucious. Old school cultural anthropologists would assume that these patrilineages are “fictive,” that they exist to bind together disparate elite lineages as a social force. To some extent this is likely true. But not entirely. The complex genetic story of the Cohens highlights that kinship may not always be fictive. In the case of the Sayyids I assume that a lot of this is fictive. When it comes to people in South Asia with the surname Khan there isn’t even a pretense that we descend in any way from a Genghiside lineage. Rather, Khan has gone from being a surname to an honorific.

In my post Patriarchy Came with Cain and Abel I connected a social phenomenon with the drastic crash in Y chromosomal effective population in the mid-Holocene, as reported in the new paper in Genome Research, A recent bottleneck of Y chromosome diversity coincides with a global change in culture. Unfortunately some of the press related to paper seems rather misleading. For example, “8,000 Years Ago, Only One Man Had Children for Every 17 Women” (here’s another take). Aside from the fact that the effective population crash only is true for a subset of lineages, like Greg Cochran I’m skeptical of the image of a winner-take-all reproductive mating market. Specifically, I don’t think there was a given generation where only ~5% of men in a given population had offspring, while the others did not. Rather, I assume that cumulative reproductive skew probably had the impact of socially privileging men from particular patrilineages, so that Y chromosomal haplotypes “swept” through the population over the course of many generations.

k10181My basic idea dovetails with Greg Clark’s in The Son Also Rises. Clark’s economic historical data sets suggests that over the long term elite lineages are surprisingly insulated from decay in status. Though there is a great deal of inter-generational churn, over the long haul there is a strong trend line of elite lineages remaining elite, and non-elite ones remaining non-elite. This may be due to cultural or genetic forces; Clark is ultimately agnostic on that. But, it suggests that social status is highly heritable. Was it always so? I suspect that these sorts of dynamics only date to the Holocene, with the rise of complex societies, and social status being connected to accumulation of material objects and power which can be passed from father to son. Additionally, with complex societies there emerged group level competitive games which were winner-take-all, as patrilineages faced off against each other with the ultimate outcome being final victory or defeat.

Ultimate this is very different from the image we have of a literal “harem society” that might emerge in small scale societies with such reproductive skew. Rather, it’s a more subtle and gradual rich-get-richer dynamic, where status and privilege compound over the generations in a genetic sense.

Addendum: Both Greg Cochran and the Genome Research paper point out that effective population does not seem to have crashed concomitantly on the autosome, as you’d expect. One minor point I’d add is that admixture can inflate population size inferences, since it elevates diversity. Most of the Holocene populations seem to have been subject to admixture, so autosomal effective population may have been artificially inflated.

Posted in Uncategorized

Comments are closed.