A friend sent me a link the other day to the top 20 most cited articles in the journal, Current Anthropology. Much to my delight, I found that a paper that I co-authored is the #7 all-time citation leader and a paper co-authored by my Stanford colleague Rebecca Bird is the #19. As I walked over to Coupa café this morning to get coffee, I realized that I also made a small contribution to the #1 on this list, Leslie Aiello and Peter Wheeler’s paper on the Expensive Tissue Hypothesis. At the time the manuscript was first circulated, I was a graduate student obsessed with brains, energetics, and scaling in human evolution. My advisor, Richard Wrangham, was asked to comment on the manuscript and he asked me if, given my obsessions, I might have something to say. Needless to say, I did. Having just read our comment, I think it stands pretty well (if I do say so): (1) basal metabolic rate (BMR) is not really a constraint and (2) what are the implications for allometric scaling of different organs with respect to body mass? Most of the expensive organs scale isometrically (that is, with a scaling exponent of one) but the brain, of course, is a big exception. It scales with an exponent closer to 3/4. Because guts and brains scale differently with increasing body mass, perhaps larger brains could be maintained by dietary compensation?
My colleague Herman Pontzer has some very interesting things to say about energetics and constraints and I’m really looking forward to some forthcoming work of his on this topic. In a paper in PNAS, he recently showed that, contrary to the expectations of a naïve trade-off model, mammals with larger home ranges actually have greater lifetime fertility and greater total offspring mass. We have a lot to learn about trade-offs, both physiological and economic, and their role in shaping human behavior and life histories.