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July 22, 2004

Pathogens & polygyny

Why Sex Matters: A Darwinian Look at Human Behavior, was written 4 years ago by Bobbie S. Low. There's a lot of interesting material in there, and she is clearly influenced by a game theoretic model of human societies. She seems to work with the maxim "build from below," starting out with a few initial assumptions that seem theoretically plausible and empirically supported. I'm still working my way through 60 pages of endnotes, but two things stuck out for me in the main text:

  • There is a difference between socially defined polygyny & monogamy and an ecological definition. While American society is monogamous (or serially monogamous) according to legal norms, ecologists might assert that it is mildly polygynous. The reason: polygyny can be defined as the ratio of male variance in reproductive success to female variance in reproductive success, in other words, fecundity skew differences. Rule of thumb: on any given trait for humans, males display more variance than females.
  • There seems to be a non-linear positive relationship between pathogen intensity and polygyny. You can read the full paper (PDF), but an implication might be that the prevalence of polygyny in much of Africa might be due to pathogenic intensity. In particular, I wonder about the impact of pathogenic coevolution in an area where hominids have been resident for millions of years.

One omission from Low's work is recent molecular genetic data that implies:

  1. The worldwide dominance of patrilocality back into prehistory can be confirmed by comparing Y & mtDNA lineages (source). Low tends to rely on cross-cultural data sets from modern 'traditional' populations .
  2. Hints at reduced Y chromosomal diversity in some populations that are known to engage in warfare and raiding on a regular basis. In other words, a rather pronounced male fecundity skew due to attrition.

Posted by razib at 11:46 PM