Chimps Grasp at Social Identities
In a group of chimpanzees now living in Tanzania's Mihale Mountains National Park, grooming partners sometimes both raise their right (or left) arms above their heads and grasp each others' wrists as they take turns cleaning one another. In a nearby Mihale chimp community studied about 20 years ago, grooming duos preferred to raise arms and clasp hands, palm-to-palm, as they tidied up one another.
This is the first evidence that chimps employ a social custom in which different communities arbitrarily modify a common behavior to identify fellow group members and foster social solidarity, proposes a team led by anthropologist William C. McGrew of Miami University in Oxford, Ohio.
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. 388). 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. 284).
Vocal dialects and other social customs proliferate in human societies. "The military salute appears to be an appropriate analogy [to chimps' grooming hand-clasps]," McGrew says. For instance, a British soldier completes a salute with the palm facing forward, whereas his U.S. counterpart holds the palm down. Although the two gestures both signal respect to a higher-ranking officer, subtle differences clearly signify a saluter's nationality.
McGrew first noted grooming chimps clasping hands in 1975 in a now-disbanded Mihale chimp group. …