However, frequencies of PPC were highly consistent within matrilines, indicating that individuals maintained lifelong fidelity to the grooming style of their mothers. We found that in the Kanyawara community (Kibale, Uganda), adults of both sexes varied widely in their PPC frequency (from 50%) and did not converge on a central group tendency. Here, we examine factors responsible for individual variation in PPC frequency within a single wild community. Because between-community differences in frequency of PPC apparently result from social learning, are stable across generations, and last for at least 9 years, they are thought to be cultural, but the mechanism of transmission is unknown. In wild communities, samples of at least 100 observed dyads grooming with raised hands showed PPC frequencies varying from 30% dyads grooming (Kanyawara, Kibale), and in a large free-ranging sanctuary group, the frequency reached >80% dyads (group 1, Chimfunshi). Palm-to-palm clasping (PPC) is a distinct style of high-arm grooming in which the grooming partners clasp each other's raised palms. High-arm grooming is a form of chimpanzee grooming in which two individuals mutually groom while each raising one arm.Other Affiliation: Department of Anthropology University of New Mexico.Other Affiliation: Kibale Chimpanzee Project Makerere University Biological Field Station Kamwenge Road.Other Affiliation: Department of Psychology University of York.Other Affiliation: National Geographic Magazine.Affiliation: Gillings School of Global Public Health, Department of Epidemiology.Other Affiliation: Department of Anthropology University of Michigan.Other Affiliation: Institute for Quantitative Social Science Harvard University.Other Affiliation: Department of Human Evolutionary Biology Harvard University.“It may be a bit like secret handshakes in human societies. “Grooming hand-clasps could provide a source of social identity for chimps,” de Waal says. Many of her comrades have since taken up the practice. In 1992, an adult female in that community first initiated grooming hand-clasps with other adults. McGrew plans to examine grooming hand-clasps in other wild chimp groups and in a captive chimp colony now being studied by Frans B.M. However, grooming partners sometimes lifted the nongrooming arms and draped their hands over low-hanging tree branches, the researchers say. Hand-clasps of either style occurred only when one partner took the lead and prompted reciprocation by the other.Īt Gombe, chimps were never reported to perform any type of hand-clasp during mutual grooming. In contrast, groomers in the other Mihale community performed hand-clasps in which one wrist crossed over the other.ĭuring hand-clasps, a grooming partner of lower social rank typically supported some of the higher-ranking partner’s weight. The now-defunct Mihale chimp group usually employed palm-to-palm clasping while grooming, McGrew’s group reports. They also inspected photos and videotapes of grooming in a nearby, still-intact Mihale chimp community observed in 19 and in a chimp group at Tanzania’s Gombe National Park studied for 40 years by Jane Goodall and others. He and his coworkers examined photographs of hand clasping taken during that expedition. McGrew first noted grooming chimps clasping hands in 1975 in a now-disbanded Mihale chimp group.
Although the two gestures both signal respect to a higher-ranking officer, subtle differences clearly signify a saluter’s nationality. For instance, a British soldier completes a salute with the palm facing forward, whereas his U.S. “The military salute appears to be an appropriate analogy ,” McGrew says. Vocal dialects and other social customs proliferate in human societies. It also adds to observations of social traditions in other animals, such as the adoption of vocal dialects by different groups of killer whales (SN: 10/28/00, p. This investigation, described in the February Current Anthropology, expands on earlier reports of separate cultural traditions in wild chimp groups (SN: 6/19/99, p.