Chimpanzees use handclasps to create social traditions
From a fist pound, to a high-five, to a firm or a weak handshake, human greetings say something about our social and cultural traditions.
Similarly, a research collaboration between the Gonzaga University and the Max Planck Institute has revealed that chimpanzees have their own social habits in the form of 'grooming handclasps'. A handclasp is the custom when chimpanzees clasp onto each other's arms, raise them into the air, and groom each other with their free arm. Researchers say the variety of ways chimpanzees do this has to do with their social behavior.
Grooming for chimpanzees has two purposes: one, to clean dirt and parasites from their skin, and two, to reinforce the bonds of family and friendship. Consequently, the way the chimpanzees practice these handclasps is indicative to the community in which they belong.
The research shows that between chimpanzee communities with similar genetic backgrounds and ecological environments, the chimpanzees reveal subtle differences in grooming handclasps. For example, one chimpanzee group highly preferred the style where they would grasp each other's hands during the grooming, while another group engaged in a clasp where they would fold their wrists around each other's wrists, where others preferred a palm-to-palm handclasp.
''We don't know what mechanisms account for these differences'', says Edwin van Leeuwen, one of the study's authors. ''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.''
The research team followed these populations and noted that young individuals developed the handclasp behavior over time. Being taught through the handclasp partnership with their mothers reveal that chimpanzees socially learn their local tradition. Van Leeuwen suggests that continued monitoring of these groups will ''shed light on the question of how these group-traditions are maintained over time and potentially even why the chimpanzees like to raise their arms up in the air during social grooming in the first place.''
Previously, traditions and cultures have been difficult to establish in animal societies due to confounding ecological and genetic factors. However, this study concludes that evidence of varying handclasps is not only motivated by genetic instincts and individual inclinations, but may also be partly cultural in nature.
To read the full article, see Proceedings of the Royal Society B.
Handclasp image via Mark Bodamer, Gonzaga University.