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brain size and pursuit-evation contests

Posted by BjoernBrembs on 21 Dec 2006 at 09:58 GMT

Mating behavior, especially in monogamous species, can be conceptualized in the context of pursuit/evasion contests. Usually, males pursue and the females evade until the female has chosen a mating partner. Another pursuit/evasion contest is predator/prey interaction. From these contests there comes evidence that predators predominantly capture small-brained prey:
Shultz S, Dunbar R (2006) Chimpanzee and felid diet composition is influenced by prey brain size. Biology Letters 2: 505-508
http://www.ncbi.nlm.nih.g...
Such a process would also select for larger brain size. Would this aspect complement or incorporate your hypothesis?

RE: brain size and pursuit-evation contests

schillaci replied to BjoernBrembs on 27 Jan 2007 at 16:49 GMT

Thank you for presenting such an interesting perspective on mating behavior and brain size evolution. Primate mating behavior, including monogamy, exists within a complex social milieu, often involving more than two participants. Although predator/prey interactions often may include more than two participants, I am not sure your analogy is entirely correct. Felids, for example, are not typically collective or social hunters, while Chimps are. How would social complexity influence the evolution of larger brains in predators? Shultz and Dunbar (2006) propose that brain size evolution is driven in part by selection for more sophisticated and behaviorally flexible anti-predator behavior. Using your model, and assuming males are predators, wouldn’t small-brained female prey be captured (copulate) more frequently and therefore have higher fertility than the large-brained harder to capture females who have more sophisticated anti-predator cognitive adaptations? If so, your predator/prey interaction model for understanding primate brain evolution would predict directional selection for smaller brains over subsequent generations. In addition, predator/prey interactions (i.e., interactions among potential mates) would vary considerably across mating systems. Nevertheless, you present an interesting perspective that warrants investigation.

RE: brain size and pursuit-evation contests

BjoernBrembs replied to schillaci on 02 Feb 2007 at 15:15 GMT

Excellent points! Maybe I should have made my initial comment less brief and more elaborate.
I'm not a primate specialist, so please correct me where my assumptions are wrong. I assumed that "rape" did not happen among non-human primates and that it is thus the female who decides if a copulation takes place or not (and not the male). Therefore I generalized from the predator/prey interaction in Shultz and Dunbar (2006) to incorporate more broadly all sorts of pursuit/evasion contests. In this view, the female primates in monogamous species chose the male with the most variable, unpredictable and surprising behavior (which also has the largest brain). The brain size of the female would be either independent, or may even be correlated such that the females with the best capacity to evade mating with the males with the best capacity to pursue. Where I am not quite sure is how brain-size correlates with the social status of the female?
Thank you for your reply. I really like your work. I'm looking forward to further resarch in his area.

RE: RE: brain size and pursuit-evation contests

schillaci replied to BjoernBrembs on 07 Feb 2007 at 17:21 GMT

Female mate choice is variable among primates, so your predator avoidance model might be applicable for some mating systems, such as multi-male/multi-female, but not others. I am not sure that brain size would be a good predictor of social status or rank in primates, but that would not have to be a problem for your model. It may be that high social intelligence facilitates favorable mate choice. That would be compatible with both of our models for the evolution of primate brain size.