Fraternities have handshakes.
Summer camps have catch phrases.
Chimpanzees have arm motions.
A new study from the Max Planck institute has found evidence that individual chimpanzee populations pass down different versions of a "grooming handclasp" as a proto "cultural tradition":
"Even between chimpanzee communities that engage in the grooming handclasp, subtle yet stable differences exist in the styles that they prefer," the study found. "One chimpanzee group highly preferred the style where they would grasp each other’s hands during the grooming, while another group engaged much more in a style where they would fold their wrists around each other’s wrists.
"We don't know what mechanisms account for these differences", van Leeuwen says. "But our study at least reveals that these chimpanzee communities formed and maintained their own local grooming traditions over the last 5 years. Our observations may also indicate that chimpanzees can overcome their innate predispositions, potentially allowing them to manipulate their environment based on social constructs rather than on mere instincts."
Here's a video of the move: