No, Action Potential is not going to start giving dating advice…yet. I just needed a catch-all title for a catch-all blog entry. After last week’s ugly Watson debate, I figured that I would return to research science and have a little fun updating you on some recent primate research. The usual caveat applies to this entry, as with many of mine, that the neuroscience links are tenuous. Of course, that depends on your definition of neuroscience. Since mine is quite broad, it looks like we can proceed.

In the last few weeks, several studies have come out reporting on characteristics of our primate brethren. Reporting in Current Biology, Marc Hauser and his collaborators compared people with chimps in a head-to-head test of patience. The researchers used a classical experiment in which subjects learn that they can either accept a smaller reward immediately, or wait for a larger reward. Previous studies had demonstrated that many animals, including other monkey species, rarely wait for the larger reward (most lasting only seconds before selecting the immediate gratification). Chimps were not only willing to wait for minutes in order to receive a larger food reward (much longer than any other species tested), but were also more patient than humans in the head-to-head test. Lest we feel inadequate in the face of this great loss, the authors then tested humans on a similar task in which the reward was not food, but money. In this task, when the results were normalized, chimps and humans had equal capacity for patience in order to reap greater benefit. Therefore, humans and chimps (and bonobos as well) are the few species that demonstrate a presumed capacity to take into account future events when making temporal choices. Thus, as Chaucer wrote in The Canterbury Tales (1386), “Patience is a virtue high” not only for humans, but also for our closest relatives.

Moving on to a different characteristic, Keith Jensen and colleagues concluded that unlike humans, chimps are “rationale maximizers.” What the heck does that mean? These findings were published in Science, and the phrase basically means that chimps lack a sense of fairness. In the ultimatum game, previously only given to humans, subjects are matched, with the “proposer” dividing up an arbitrary reward, and the “responder” accepting or rejecting the proposal. If the proposal is rejected, neither party gets anything. Almost universally, humans will reject any division in which they receive less than 20%, likely because the proposal was deemed to be unfair. In a cleverly adapted version of the ultimatum game, chimps, on the other hand, accept any proposal in which their share is not zero. The researchers thus propose that an aversion to inequality, even at a personal expense, could be a key differentiating factor between humans and chimps. This is a key conclusion for some researchers who believe that placing a premium on fairness is what has allowed human society to become so large and complex.

Finally, getting the girl. Human machismo exists for an evolutionary reason, right? It is a way of proving one’s physical prowess and genetic fitness. In chimps, sharing wild plant foods is uncommon, however, in those troops that hunt, the sharing of meat can influence social bonding and relationships. Thus, the apparent danger inherent to hunting is hypothesized to signal the fitness of the bearer of meat. New data supporting this theory of [thwarting danger = fitness] was recently published in PLoS ONE. Researchers observed the sharing of plant foods amongst chimps, which at first glance refutes previous findings and hypotheses. However, a closer inspection revealed that the specific plants being shared were cultivated foods, stolen from nearby farm fields. Even more interestingly, the food was primarily received by a reproductively cycling female from a male, suggesting that food raiding, a dangerous endeavor, may be another means of proving the fitness of the successful male. The presumed trading of commodities (coveted food in exchange for sex or grooming) provides an exceptional crop raider with the currency to get the girl. This obviously isn’t fair to the chimp who lacks the courage to sneak into an angry farmer’s field for papaya, but who said that chimps are fair???

Rosati, A., Stevens, J., Hare, B., & Hauser, M. (2007). The Evolutionary Origins of Human Patience: Temporal Preferences in Chimpanzees, Bonobos, and Human Adults Current Biology, 17 (19), 1663-1668 DOI: 10.1016/j.cub.2007.08.033