Wild chimps scale branches of culture

A new analysis of behavioral traditions practiced by African chimpanzees supports the idea that the animals learn about such activities from others, possibly from newcomers to established communities. Chimps thus exhibit cultural diversity, even if it falls short of the human cultural spectrum, say Stephen J. Lycett of the University of Liverpool, England, and his colleagues.

Researchers have noted 39 behaviors, varying among seven African chimp communities, that they propose as cultural acts (SN: 6/19/99, p. 388). These behaviors revolve around tool use, foraging techniques, and grooming methods. Critics argue that genetic characteristics of different chimp communities, not culturally based learning, may foster distinctive behavioral styles.

Lycett’s team examined chimp traditions using cladistics, a technique previously employed to identify branching evolutionary relationships among fossil organisms, spoken languages, and even ancient stone arrowheads. The method involved comparing chimp behaviors with those already reported for closely related bonobos, or pygmy chimps. The researchers defined behaviors shared by chimps and bonobos as having been precursors of those unique to chimps.

Branching patterns of related behaviors appeared in each chimp community and in sets of communities from either eastern or western Africa, the researchers report in the Nov. 6 Proceedings of the National Academy of Sciences. These localized connections among behaviors arose via cultural transmission, they posit. In contrast, no behavioral pattern was common to eastern and western African chimps. The absence of continentwide structure suggests that no link exists between genetic and cultural differences among chimps.

Cultural traditions spread relatively slowly as female chimps emigrate to nearby groups at sexual maturity, the scientists propose. Female newcomers may also abandon traditions from their native groups in favor of approaches taken by their new comrades, they note.