Chimps’ secret handshakes, the hand-holding behavior that takes place during grooming, might be a sign that chimpanzees have distinct and differing cultures, new research has found.
Chimps use grooming to bond, relax, and get rid of parasites, and, in some groups, this ritual is accompanied by a special type of over-the-head hand-holding, LiveScience reported.
The chimps’ secret handshakes are not seen in all groups of chimpanzees, and the exact mechanisms of each handshake appears to vary from group to group in ways that researcher believe aren’t dependent on genetics or environment, LiveScience reported.
For researchers, that points to cultural differences between chimp groups as the reason for the differing handshakes.
“We think that this at least indicates that chimpanzees do not only respond to their environment instinctively or based on genetic predisposition,” said study researcher Edwin van Leeuwen, a doctoral student at the Max Planck Institute for Psycholinguistics in the Netherlands. “They can have a shared community tradition.”
The chimps’ secret handshakes were first studied in Tanzania and have since been seen in 15 other chimp communities. Other chimp groups appear never to hold hands during grooming.
Observations revealed that the chimps’ secret handshakes were passed down from generation to generation, the Telegraph reported.
“By following the chimpanzees over time, we were able to show that 20 young chimpanzees gradually developed the handclasp behaviour over the course of the five-year study,” said Mark Bodamer of Gonzaga University. “The first handclasps by young individuals were mostly in partnership with their mothers. These observations support the conclusion that these chimpanzees socially learn their local tradition, and that this might be evidence of social culture.”
After studying groups of chimps at a sanctuary for more than 1,000 hours over the past two years, van Leeuwen and his colleagues found that of the four distinct groups, two chimp groups never used secret handshakes. The other chimp groups did hold hands, but did it differently; one group always grasped palm-to-palm, while the other hooked their wrists around each other.
“The indication might be that chimpanzees have the capacity at least to respond to their environment with more flexibility,” van Leeuwen said of the chimps’ secret handhsakes. “It’s social flexibility and that’s of course what we definitely see in humans.”