'Cultured' chimpanzees pass on novel traditions

The local customs that define human cultures in important ways also exist in the ape world, suggests a study reported online June 7th in Current Biology, a Cell Press publication. Indeed, captive chimpanzees, like people, can readily acquire new traditions, and those newly instituted "cultural practices" can spread to other troops.

"We have robust evidence that in chimpanzees there is a considerable capacity for cultural spread of innovations," said Dr. Andrew Whiten of the University of St. Andrews in Scotland. "This strengthens the interpretation of cases of behavioral diversity in the wild as socially transmitted traditions. Moreover, we have now shown that chimpanzees can sustain cultures that are made up of several traditions. This again is consistent with what is seen in the wild, where chimpanzees are thought to show up to 20 traditions that define their unique local culture."

Documented examples of behavioral differences among chimpanzees in nature include various types of tool use, including hammers and pestles; social behaviors like overhead hand-clasping during mutual grooming; courtship rituals like leaf-clipping, in which leaves are noisily clipped with the teeth; and methods for eradicating parasites by either stabbing or squashing them. However, the idea that such behaviors constitute traditions passed on through observational learning "relies heavily on circumstantial evidence that alternative genetic or environmental explanations are implausible."

Now, Whiten's international team, including colleagues in Scotland and others from Emory University's Yerkes National Primate Research Center and the University of Texas, has tackled the question experimentally by "seeding" novel forms of tool use and food extraction in different captive chimpanzee communities.

Over time, the researchers saw ten of these new behaviors spread and become full-fledged, local traditions. As a result, the communities at Yerkes and the University of Texas now display their own unique cultures.

At the University of Texas, where several groups are next-door neighbors within eyeshot of each other, four of the new traditions proved catching. The learned foraging practices spread from one group to another, and then on to a third.

The findings have important implications for understanding the ability of primates to adapt over time.

"Social learning is important for evolutionary adaptation because it can be so much faster than that which occurs through genetic change; and, unlike learning by one's own efforts-for example, by trial and error-it can be very efficient because one is standing on the shoulders of what previous generations achieved," Whiten said.

Cell Press. June 2007.