Friday, October 05, 2007

Sex-biased dispersal....   posted by Razib @ 10/05/2007 12:03:00 PM

Apropos of my post about patrilocality and genetics, here's an article (Open Access), Female-biased dispersal and patrilocal kin groups in a mammal with resource-defence polygyny:
Female-biased dispersal (FBD) is rare among mammals (e.g. African wild dogs Lycaon pictus...Chimpanzees Pan troglodytes...and its occurrence frequently correlates with resource-defence polygyny...However, a resource-defence strategy does not necessarily lead to FBD...and there are examples of mammals with FBD that do not follow a resource-defence mating strategy...In a considerable number of polygynous mammalian species, females may disperse to avoid inbreeding with their fathers when male tenure exceeds female age at first conception...In the greater sac-winged bat (Saccopteryx bilineata), females have been reported to disperse from their natal colony, whereas at least some of the male progeny remain in their natal colony...The mating system of this bat is best described as resource-defence polygyny...this would mean that females are assumed to disperse owing to the inbreeding risk arising from male philopatry. However, there are currently no studies investigating the causes for female dispersal in this species and if there is a risk of inbreeding arising from female breeding philopatry and male natal philopatry.

Well, humans aren't bats. That being said, I wonder if philopatry is critical in inducing males to be "good dads." While females have perfect certainty as to who their offspring are, male paternity confidence is less assured. Matrilineal and matrifocal societies seem to be optimal scenarios for males not investing in their offspring because of lack of certainty and social supports for males (this is why maternal uncles loom large in many cultures). In contrast, patrilineal and patrifocal societies may serve as watchdogs which guarantee paternity certainty so that males can maximize their fitness by investing in their own offspring. If a man moves to live with his wife's family it seems likely that if she engaged in infidelity the chances would be far higher than not that her relatives would cover up for her; after all the coefficient of relatedness likely increases rather than decreases since the lover is likely to be a local.