Jones & Bird (2008) == Evolutionary Psychology???

So, I've been spending a bunch of time recently thinking about evolutionary psychology (EP). This is a field about which I have some serious reservations for a variety of reasons both technical and philosophical. That said, I do find the constant in-fighting among human evolutionary biologists tedious and think that it's absurdly unproductive. I am currently working on a critique of some particular aspects of contemporary thought in EP and these blog posts have helped me to get some of my thoughts in order. I am also working on trying to find common ground with researchers in a variety of different "schools" of human evolutionary studies.

Rebecca Bird and I recently wrote a short essay published in Anthropology News that defends functionalist approaches to the study of human ecology (a position that, given the reaction of the editor, is rather controversial). Given the severe length constraints we faced, we were only able to give the barest outline of the research program in human evolutionary ecology that we are trying to establish at Stanford (see this previous post for some details). This is neither the place nor the time to elaborate on the argument of the essay, but I will re-cap a couple points:

  • Contemporary ecological (or environmental) anthropology has ceded explanations of human behavior based on rationality to economists
  • Allowing pure economic (i.e., pecuniary) rationality to define what we collectively consider "rational" is dangerous and ill-considered
  • Expectations of group and/or individual rationality may fail because of a failure to consider the correct objective function, individual heterogeneity, or key trade-offs
  • "Culture" is an amalgam of behaviors and institutions that represent responses to both past and present environments and as such is not particularly useful as a causal explanation for observed behavior

We also suggest some crazy methodological ideas like measuring things and testing multiple competing hypotheses.

The point I want to take up right now is the failure of observing the predictions of rational-actor models because of the failure to account for trade-offs. Rebecca and I had one particular trade-off in mind when we wrote this. We hypothesize that there is frequently a very general trade-off between pecuniary reward and social capital. This arises from the fact that, on the one hand, sharing (especially food-sharing) is so ubiquitous in face-to-face human groups and, on the other hand, people frequently engage in social signaling specifically through economically costly activities (see Bird and Smith (2005) for a review). It would not surprise us at all if it turned out that people were much better at solving complex social optimization problems than they are at optimizing pecuniary return.

Now, in my holiday-induced state of heightened self-reflection, it occurs to me that this argument is really not all that different from Leda Cosmides's (1989, et seq.) suggestion that people are better at solving the Wason selection test when it is presented in terms of social contracts than when it is presented in its traditional way as a test of abstract logical reasoning abilities. Yikes! Does this mean that Rebecca Bird and I are evolutionary psychologists? No, it doesn't. It does make me think that perhaps the time has come for détente among the different schools of thought working on evolution and human behavior. I'm hardly the first person to think this (See Eric Smith's (2000) paper for instance). But maybe I'm the first to blog it!

My Stanford colleagues Rebecca and Doug Bird are clearly leading figures in contemporary human behavioral ecology. I will let their work and the philosophy it entails stand for itself. In what follows, I will focus on my own philosophical and methodological orientation. (Perhaps they will comment on this entry at some point...)

Martin Daly and Margo Wilson (who I think generally do excellent work) rather infamously and imperialistically claimed in a 1999 review article in Animal Behaviour that EP "encompasses work by nonpsychologists, including even those who have deliberately differentiated themselves from 'evolutionary psychology' as 'evolutionary anthropologists', 'human sociobiologists' and 'human behavioural ecologists'." This led to a rebuttal paper by three eminent Human Behavioral Ecologists (Eric Smith, Monique Borgerhoff Mulder, and Kim Hill) (Smith et al. 2000). This is an excellent paper and I heartily recommend anyone interested in evolution and human behavior read the exchange, which is freely available here and here. I will defer to the Smith et al. (2000) paper for the bulk of the arguments on why it is not reasonable to think of HBE (and other approaches) as a subset of EP, but will highlight a couple here:

  • HBE actually pre-dates EP as a field
  • Prominent EP practitioners were the ones who advocated the separation in the first place, largely on theoretical grounds
  • There are substantial theoretical and methodological differences that characterize the two fields

The one issue that I will take up relates to my personal sensibility with regard to science. A tenet of EP is that contemporary behavior -- and the fitness outcomes of this behavior -- is irrelevant for evolutionary understanding. The contention is that we should instead focus on the study of the psychological mechanisms underlying behavior. The idea that current behavior and/or fitness is irrelevant comes across indirectly in Donald Symons's (1989) critique of "Darwinian Anthropology" and more directly and forcefully in Tooby and Cosmides's (1990) follow-up "The Past Explains the Present: Emotional Adaptations and the Structure of Ancestral Environments." I don't want to come across as too much of a de Finetti-style positivist here, but I have a hard time with the idea that we should sacrifice studying observables in favor of objects that we have no hope of observing. While I don't object to studying psychological mechanisms, I do think that since the thing we are interested in explaining is human behavior, perhaps that is what we should study.

But now I find myself confronted with the fact that I have made an EP-like argument in print (albeit Anthropology News!) as well as the very real fact that I have always found Cosmides and Tooby's argument about social reasoning and the Wason selection test compelling. Perhaps the lesson here is that we shouldn't be idealogues with regard to our approach to science. While I will admit a distressingly positivist love of observables (a common feature of Bayesians?), my true philosophical heritage lies in the works of Peirce, James, and Dewey. As a committed pragmatist, I am willing to at least entertain just about any theoretical or methodological position that helps me solve scientific questions.

What if every student of human behavior wrote a paper in which they adopted the approach of a contrasting school? Would this be cool or would it simply be anarchic?

There are some ways in which it is perhaps easier for me to think across these schools than some of my colleagues. My dirty little secret is that I was never really trained in any of them! My graduate training is in (nonhuman) primate behavioral ecology. One of the most influential people for my intellectual and personal development (and probably the only reason I actually got into Harvard) is Irv DeVore, a foundational figure for EP. My Ph.D. advisor Richard Wrangham, while very much a behavioral ecologist when studying chimpanzees, is clearly sympathetic to EP when studying humans. In my post-doc, I moved into more applied questions of human health and population dynamics and indirectly encountered one of the other "schools" of human evolutionary thought, namely, dual-inheritance theory. Cultural transmission models are used in health research to understand the adoption of things like modern contraception or oral rehydration therapy. As a result, I have thought a little about models of cultural transmission (a chapter that I wrote in Melissa Brown's recent book can be found here). This is a pretty natural extension of my work in epidemic modeling and while it is not a central part of my research, I suspect I haven't said my last on the topic (particularly not if I continue to attract clever students interested in the topic).

So, those are my thoughts du jour on the study of human behavior. The winter break is rapidly drawing to a close and pretty soon I will be back in the office and will need to get back to actual research. Hopefully, these meditations in the closing days of 2008 will have a positive influence on this research.


Bird, R. B., and E. A. Smith. 2005. Signaling Theory, Strategic Interaction, and Symbolic Capital. Current Anthropology 46 (2):221-248.

Cosmides, L. 1989. The Logic of Social Exchange: Has Natural Selection Shaped How Humans Reason? Studies with the Wason Selection Task. Cognition 31: 187-276.

Daly, M., and M. I. Wilson. 1999. Human Evolutionary Psychology and Animal Behaviour. Animal Behaviour 57:509-519.

Smith, E. A. 2000. Three Styles in the Evolutionary Study of Human Behavior. In Human Behavior and Adaptation: An Anthropological Perspective, edited by L. Cronk, W. Irons and N. Chagnon. Hawthorne, NY: Aldine de Gruyter.

Smith, E. A., M. Borgerhoff Mulder, and K. Hill. 2000. Evolutionary Analyses of Human Behaviour: A Commentary on Daly & Wilson. Animal Behaviour 60:F21-F26.

Symons, D. 1989. A Critique of Darwinian Anthropology. Ethology and Sociobiology 10 (1-3):131-144.

Tooby, J., and L. Cosmides. 1990. The Past Explains the Present - Emotional Adaptations and the Structure of Ancestral Environments. Ethology and Sociobiology 11 (4-5):375-424.

2 thoughts on “Jones & Bird (2008) == Evolutionary Psychology???”

  1. A critical aspect of applying economic analysis to human actions is to choose the proper discount rate, something which is never explicitly done (that I am aware of). If you choose the proper discount rate, then some seemingly inexplicable actions become explainable, as why HIV negative drug users will share needles with people they know are HIV positive. If your discount rate is infinite, then stuff that happens in a few years, months, days or even minutes doesn’t matter. I think this explains why punishment fails to deter the stimulant drugs of abuse (and other things too). If your discount rate is infinite, no punishment in the future can possibly be a deterrent.

    I think that extreme life-or-death stress increases the discount rate and in the limit to infinity. This is what allows organisms to run themselves to death while trying to escape from a predator.

    I think this is done automatically and is a side effect of the regulation of ATP via NO. As the archetypal “need”, presumably pathways to satisfy and ATP need evolved first. As later needs became important, presumably ATP satisfying pathways were co-opted to regulated the other needs. Stress is a low NO state, and so is a low ATP state. Cells use ATP as a control parameter to regulate ATP consumption. When there isn’t enough ATP, long time constant pathway and non-essential pathways get turned off to conserve ATP for immediate consumption. This is commonly observed as ischemic preconditioning, where brief periods of ischemia (which causes brief instances of ATP depletion) causes the cell to change to a state where longer periods of ischemia are survivable.

    I think a self-perception of need as mediated by basal NO levels regulating the discount rate explains how it changes under stress. If you make people desperate, they will do desperate things because their discount rate has been increased.

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