Handshakes in chimpanzee culture

Chimp Groups Have Their Own Distinct “Handshakes” https://t.co/LhNth6KQiY

— Bill Benzon, aka The Danish Space Laser (@bbenzon) June 22, 2021

From the article linked in the Tweet:

Over a 12-year span, two groups of chimpanzees maintained distinct, consistent styles of clasping hands while grooming one another, according to a study published May 26 in Biology Letters. The study findings represent a step forward in understanding chimp sociality and chimp culture—the behavioral patterns that are learned from others in a social group.

“The fact that different groups of chimps have different repertoires of gestures is something we’ve known for some time,” says Mary Lee Jensvold, the associate director of the chimp sanctuary Fauna Foundation, who was not involved in the research, but it was not clear how stable these behaviors were. “The longevity of [this study] is new,” she adds, noting that the semi-wild setting of the Chimfunshi Wildlife Orphanage Trust in Zambia where the research was conducted means that the study’s findings likely apply to wild chimps, too.

Chimp researcher William McGrew, then affiliated with the University of St. Andrews in Scotland, first reported observing handclasp grooming in wild chimps in 1978, and this behavior among chimp dyads has attracted increasing research interest in recent years. While the function of handclasping is not known, University of Antwerp researcher Edwin van Leeuwen, the study’s author, says he’s not bothered by the ease of comparing these handclasps to human handshakes, themselves a cultural behavior.

“We now have a lot of evidence of cultural differences across wild chimpanzee study sites, but much of that is about tool use and foraging behavior, so this evidence concerning a social custom is particularly valuable,” Andrew Whiten of the University of St. Andrews, writes in an email to The Scientist. He was not involved in this latest work but collaborates with van Leeuwen.

Handclasping behavior is unique among cultural characteristics of chimp groups in the sense that it does not appear to directly promote chimp survival. “To the best of my knowledge, this handclasp grooming is the only convincing evidence of social conventions in chimpanzees,” Susan Perry, an evolutionary anthropologist and field primatologist at the University of California, Los Angeles, who was also not involved in the work, writes in an email to The Scientist.

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