A seemingly spontaneous conga line by a pair of captive chimpanzees might tell us something about how humans first learned to dance, scientists behind a new study say.
For years, visitors to the Saint Louis Zoo occasionally spotted and filmed a perplexing display from two closely bonded female chimpanzees named Holly and Bahkahri: They would walk and sway in sync along their habitat, usually each carrying a blanket underneath them, almost as if they were dancing a rudimentary conga line.
In a new study published Thursday in Scientific Reports, researchers from Europe say there’s ample evidence to suggest the chimps’ routine was neither an accident nor the product of human training. And they even argue that the discovery could help establish a new theory about how dance first evolved in humans.
The researchers studied more than a dozen YouTube videos of the pair’s conga line taken between 2011 and 2015. Creating a model of their movements, they concluded that the “dance” was an entirely purposeful ritual that the pair had well established between themselves.
The chimps, they wrote, “exhibited a gait movement that was individually regular and mutually synchronised, demonstrating joint rhythm keeping. Whenever one individual accelerated or decelerated her pace, her partner matched her pace.”
It’s also unlikely that the two were ever trained to carry out their rhythmic performance by their zoo handlers, given that the practice of training chimps for entertainment had been phased by the St. Louis Zoo in the 1980s, and they had arrived close together when they were four months old in 1998. Nor is it likely that they would have picked up a fairly complicated behaviour incidentally from watching humans, the authors said.
While other animals have been observed moving their bodies rhythmically to sounds or in response to another member of their species the way humans do, this seems to be the first time any animals besides us have been shown to display this sort of behaviour spontaneously, without any kind of external stimulus like music, according to the authors.
In this case, it’s likely that the dance arose as a coping behaviour for the two chimps. While they were eventually accepted into the family at the zoo, both chimps were deprived of their mothers and a healthy environment early on in their lives, which can obviously affect both humans and nonhuman primates pretty dramatically. Being so closely bonded, the synchronised swaying might have been a stress reliever, much like a baby sucking its thumb.
Indeed, the Saint Louis Zoo has said as much. The zoo’s public relations director, Susan Gallagher, told local outlet KSDK in 2017 that the two chimps had been “dancing” since infancy.
“As adults, Holly and Bakhari socialise with all the other members of their group and behave like the chimpanzees they are,” she said, “But there are still times when the two best friends seek each other out for the familiar tactile comfort they offer each other.”
But the very fact that chimps have the capacity to adopt this behaviour, the study’s authors argue, is reason enough to suspect the origins of dance in humans might have been a multi-step process that didn’t even involve music initially. And similar to Holly and Bahkahri, maybe it was a behaviour first practiced by close-knit groups of proto-humans in stressful situations.
Of course, there’s only so much we can infer about our own evolution from observing our relatives in captivity. So there’s a lot more work that needs to be done in untangling how and why we first learned to dance.
Sadly for her dance partner Bakhari, Holly the chimpanzee died in 2018 at age 19 from advanced cancer.