Cross-posted with the permission of Dr. Nathan H. Lents from his The Human Evolution Blog.
Mandrills are, literally, one of the most colorful creatures on earth and certainly the most colorful primates. Their striking faces are matched only by the bright coloring of their hindquarters. (Their genitals are colorful, too, if you must know!) The coloring is part of their sexual displays, and the males are much more colorful than the females. The unique coloring made mandrills popular with children even before Rafiki stole the show in The Lion King.
Mandrills are also the subject of a curious new discovery. Professor Mark Laidre, now of Dartmouth University, has observed more than 30 separate communities of mandrills while studying their social activities and structures. In one such community – a zoo in Colchester England, it appears that a gesture has been invented.
The gesture in question is simply covering the face with one hand, like a face-palm, and holding it for several minutes, sometimes up to a quarter of an hour. The mandrills do this in the shade as much as the direct sun and independent of wind conditions. After studying the monkeys as they made the gesture, Laidre hypothesized that it was a “do not disturb” signal that the mandrills use when they want to be left alone.
To test this, he carefully documented the behavior of nearby mandrills and found that, during the time that a mandrill was making the gesture, there was significantly reduced social advances by other mandrills. Fewer mandrills approached the gesturing mandrill, and fewer touched him or her, compared to mandrills in similar postures but not making the gesture. The gesture really does seem to mean “leave me alone.”
This is the first documented example of an intentional unambiguous gesture in any non-ape primate species. However, that is not even the most interesting part. This gesture was “invented” in one particular community of mandrills in an English zoo and has since spread through that community. It has never been seen in any other community of mandrills, despite Laidre and many others looking.
The transmission of knowledge and practices is the hallmark of culture. Accordingly, Professor Laidre titled his paper, “Meaningful Gesture in Monkeys? Investigating whether Mandrills Create Social Culture.” Laidre is correct that this example of gestural communication meets all the usual criteria for social cultural transmission: the behavior is learned, not instinctual, it is unique to a specific community, and it has remained stable despite demographic changes in the community (births, deaths, etc.).
The experiment that would clinch this would be to exchange mandrills from other zoos to see if the gesture can spread into different communities. If so, that would provide another window into the evolution of language.
Written by Prof. Nathan H. Lents
Professor Nathan H. Lents is a tenured associate professor of molecular biology at John Jay College of the City University of New York, a visiting professor at the University of Lincoln (UK), and author of "Not So Different: Finding Human Nature in Animals" (Columbia University Press, 2016). Professor Lents conducts research in three areas: forensic botany, the human microbiome, and teaching/learning biology at the college level. His work has been funded by the NIH, NSF, US Dept. of Ed, and the Susan G. Komen Breast Cancer Foundation. He also maintains The Human Evolution Blog and authors most of its content.