Holly and Bahkahri are sisters of sorts. The two chimpanzees were born at different facilities just two weeks apart in 1998 and wound up at the St. Louis Zoo at 4-months-old within one day of each other. They also share a unique talent: dancing.
The chimpanzee duo is the first to be observed swaying their hips from side-to-side, engaging in coordinated and synchronized “whole-body rhythmic entertainment,” which researchers say may provide insight into the evolution of human dance.
“Dance is an icon of human expression. Despite astounding diversity around the world’s cultures and dazzling abundance of reminiscent animal systems, the evolution of dance in the human clade remains obscure,” said study author Dr Adriano Lameira, University of Warwick, in a statement.
“Dance requires individuals to interactively synchronize their whole-body tempo to their partner’s, with near-perfect precision, this explains why no dance forms were present amongst nonhuman primates. Critically, this is evidence for conjoined full-body rhythmic entrainment in great apes that could help reconstruct possible proto-stages of human dance is still lacking.”
Other species have been seen moving to the beat (remember Snowball, the head-banging cockatoo?), but never have two nonhuman animals have been spotted moving to their own beat without being triggered or signaled by humans. Dancing requires that two individuals coordinate together with great motor control using multiple neural circuitries, as well as a developed social bond between the two. Until now, these complexities explained why nonhuman primates did not dance.
To study this behavior, researchers from the University of Warwick, Durham University, and the Free University of Brussels searched for videos of the dancing chimpanzees that had been uploaded to YouTube using terms like “conga line,” “chimpanzees,” or “St Louis”. A total of 23 videos spanning between October 2011 and April 2015 were then analyzed for time and movement measures.
“Between individual analyses, however, revealed that synchronization between individuals was non-random, predictable,” write the authors in Scientific Reports, adding that the movements were maintained with precision and seeming intention as each chimpanzee took turns taking on the role of “pacemaker”.
This "dance" evolution may be influenced by the animals being in captivity and by certain ecological, social, and cultural impositions that come with such an environment. It has also only been observed in two individuals, so it is difficult to draw conclusions from it. This sort of “human proto-dance” may be rooted in social dynamics unique to small groups who benefit from mutual touch and moving rhythmically at the same time in a “rhythmic social ritual”.