The Compassionate Instinct

Continuous study of the troop has yielded some insights into how its culture is transmitted to newcomers. Genetics obviously plays no role, nor apparently does self-selection: adolescent males that transfer into the troop are no different from those that transfer into other troops, displaying on arrival similarly high rates of aggression and low rates of affiliation. Nor is there evidence that new males are taught to act in benign ways by the residents. One cannot rule out the possibility that some observational learning is occurring, but it is difficult to detect, given that the distinctive feature of this culture is not the performance of a unique behavior but the performance of typical behaviors at atypically extreme rates.

To date, the most interesting hint about the mechanism of transmission is the way recently transferred males are treated by Forest Troop’s resident females. In a typical savanna baboon troop, newly transferred adolescent males spend years slowly working their way into the social fabric; they are extremely low ranking—ignored by females and noted by adult males only as convenient targets for aggression. In Forest Troop, by contrast, new male transfers are inundated with female attention soon after their arrival. Resident females first present themselves sexually to new males an average of 18 days after the males arrive, and they first groom the new males an average of 20 days after they arrive, whereas normal savanna baboons introduce such behaviors after 63 and 78 days, respectively. Furthermore, these welcoming gestures occur more frequently in Forest Troop during the early post-transfer period, and there is four times as much grooming of males by females in Forest Troop as elsewhere. From almost the moment they arrive, in other words, new males find out that in Forest Troop, things are done differently.

At present, I think the most plausible explanation is that this troop’s special culture is not passed on actively but simply emerges, facilitated by the actions of the resident members. Living in a group with half the typical number of males, and with the males being nice guys to boot, Forest Troop’s females become more relaxed and less wary. (This is so, in part, because in a typical baboon troop, a male who loses a dominance interaction with another male will often attack a female in frustration.) As a result, they are more willing to take a chance and reach out socially to new arrivals, even if the new guys are typical jerky adolescents at first. The new males, in turn, finding themselves treated so well, eventually relax and adopt the behaviors of the troop’s distinctive social milieu.

NATURAL-BORN KILLERS?

Are there any lessons to be learned here that can be applied to human-on-human violence—apart, that is, from the possible desirability of giving fatal cases of tuberculosis to aggressive people? Can human behavior be as malleable—and as peaceful—as Forest Troop’s?

Any biological anthropologist opining about human behavior is required by long-established tradition to note that for 99 percent of human history, humans lived in small, stable bands of related hunter-gatherers. Game theorists have shown that a small, cohesive group is the perfect setting for the emergence of cooperation: The identities of the other participants are known, there are opportunities to play games together repeatedly (and thus the ability to punish cheaters), and there is open-book play (players can acquire reputations). And so, those hunter-gatherer bands were highly egalitarian. Empirical and experimental data have also shown the cooperative advantages of small groups at the opposite human extreme—namely, in the corporate world.

But the lack of violence within small groups can come at a heavy price. Small homogenous groups with shared values can be a nightmare of conformity. They can also be dangerous for outsiders. Unconsciously emulating the murderous border patrols of closely related male chimps, militaries throughout history have sought to form small, stable units; inculcate them with rituals of pseudokinship; and thereby produce efficient, cooperative killing machines.

Is it possible to achieve the cooperative advantages of a small group without having the group reflexively view outsiders as the Other? One often encounters pessimism in response to this question, based on the notion that humans, as primates, are hardwired for xenophobia. Some brain-imaging studies have appeared to support this view in a particularly discouraging way. There is a structure deep inside the brain called the amygdala that plays a key role in fear and aggression, and experiments have shown that when subjects are presented with a face of someone from a different race, the amygdala gets metabolically active—aroused, alert, ready for action. This happens even when the face is presented subliminally, which is to say, so rapidly that the subject does not consciously see it.