Guest Blogger: Alex Pritchard
Hello BS&M fans! Sorry for the long delay between posts; we’ve had a very busy fall in BS&M land so far with lots of guest speakers and a dissertation defense (congrats to the new Dr. Sarah Hlubik!) interfering with your regularly scheduled programming. Today’s post actually comes out of a paper that we read several weeks ago and is brought to you by a member of the “Monkeys” contingent of BS&M, Alex Pritchard. Without further ado, here it is:
This week I picked an article that I really like, but, I admit, I found it difficult to convey why I like it when I presented it at our weekly journal club. The authors modeled a behavioral game using ‘savannah baboon’ energetic, reproductive, and social system parameters to test assumptions of Kirkwood’s (1977) disposable soma theory, specifically how each sex (male versus female) may have different evolutionary stable strategies for energy allocation. The disposable soma theory posits that individuals can only allocate limited energy between one of three pathways: growth, maintenance, and reproduction.
In primates, females invest considerable energy into their offspring (the reproduction pathway) and the authors use baboons, broadly, as a case study to test sexual differences in strategies. The benefits of baboons is that there is a large body of literature to use in generating a model, which factors in mortality risk, distribution of males, number of receptive females, and foraging yield. On the basis of this information, individuals then allocate energy to essential functions, growth, maintenance, and reproduction. Importantly, the individuals were informed regarding other modeled individual’s strategies. The optimal reproductive strategy (highest fitness gains) for each sex is of primary interest for the authors.
Overall, I found myself dwelling on a desire for the authors to have taken the model further and, unfortunately, to complicate it further. I think it is mostly owing to their generalization of a ‘savannah baboon,’ which combines elements of several baboon allotaxa (closely related species or subspecies). This eliminates the diversity of baboon allotaxa social systems, behaviors, mating systems, and ecologies. Behavioral distinctions are nuanced between the baboon allotaxa, and as a baboon researcher, I couldn’t help but feel that the model is compromised without at least modelling other variables; for example, male-female friendships or alternative forms of reproductive success (like consortship follows leading to sneak copulations). Broadly, this does not matter for their purposes and it is hard to find fault in this approach for the purposes of this paper. Again, they are modelling a complex system, which inherently means simplifying it to test their hypothesis regarding sexually distinct evolutionary strategies. Their model is compelling to test a wide variety of other hypotheses, however, and they suggest the model could be applied to other species living in different social systems after making some species-specific adjustments.
The required data to model such a system is fairly comprehensive, making this model only applicable to organisms that are already fairly well studied. The results, however, were impressive and their life-history outputs were, for the most part, very similar to the observed patterns. There were some exceptions to this concordance that we (the journal club) wish they had resolved. For example, the rate of aging in males and the maximum reproductive rates for both sexes.
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