Among a troop of savanna baboons in Kenya, a terrible outbreak of tuberculosis 20 years ago selectively killed off the biggest, nastiest and most despotic males, setting the stage for a social and behavioral transformation unlike any seen in this notoriously truculent primate.
In a study appearing today in the journal PloS Biology (online at www.plosbiology.org
), researchers describe the drastic temperamental and tonal shift that occurred in a troop of 62 baboons when its most belligerent members vanished from the scene. The victims were all dominant adult males that had been strong and snarly enough to fight with a neighboring baboon troop over the spoils at a tourist lodge garbage dump, and were exposed there to meat tainted with bovine tuberculosis, which soon killed them. Left behind in the troop, designated the Forest Troop, were the 50 percent of males that had been too subordinate to try dump brawling, as well as all the females and their young. With that change in demographics came a cultural swing toward pacifism, a relaxing of the usually parlous baboon hierarchy, and a willingness to use affection and mutual grooming rather than threats, swipes and bites to foster a patriotic spirit.
Remarkably, the Forest Troop has maintained its genial style over two decades, even though the male survivors of the epidemic have since died or disappeared and been replaced by males from the outside.... The persistence of communal comity suggests that the resident baboons must somehow be instructing the immigrants in the unusual customs of the tribe.
Dr. Sapolsky, who is renowned for his study of the physiology of stress, said that the Forest Troop baboons probably felt as good as they acted. Hormone samples from the monkeys showed far less evidence of stress in even the lowest-ranking individuals, when contrasted with baboons living in more rancorous societies.
The new work vividly demonstrates that, Putumayo records notwithstanding, humans hold no patent on multiculturalism. As a growing body of research indicates, many social animals learn from one another and cultivate regional variants in skills, conventions and fashions. Some chimpanzees crack open their nuts with a stone hammer on a stone anvil; others prefer wood hammers on wood anvils. The chimpanzees of the Tai forest rain-dance; those of the Gombe tickle themselves. Dr. Jane Goodall reported a fad in one chimpanzee group: a young female started wiggling her hands, and before long, every teen chimp was doing likewise.
But in the baboon study, the culture being conveyed is less a specific behavior or skill than a global code of conduct. ''You can more accurately describe it as the social ethos of group,'' said Dr. Andrew Whiten, a professor of evolutionary and developmental psychology at the University of St. Andrews in Scotland who has studied chimpanzee culture. ''It's an attitude that's being transmitted.''
The report also offers real-world proof of a principle first demonstrated in captive populations of monkeys: that with the right upbringing, diplomacy is infectious. Dr. Frans B. M. de Waal, the director of the Living Links Center at the Yerkes National Primate Research Center of Emory University in Atlanta, has shown that if the normally pugilistic rhesus monkeys are reared with the more conciliatory stumptailed monkeys, the rhesus monkeys learn the value of tolerance, peacemaking and mutual hip-hugging.
Dr. de Waal, who wrote an essay to accompany the new baboon study, said in a telephone interview, ''The good news for humans is that it looks like peaceful conditions, once established, can be maintained,'' he said.
''And if baboons can do it,'' he said, ''why not us? The bad news is that you might have to first knock out all the most aggressive males to get there.''