Psychologist observing two chimpanzees in a zoo have discovered that they performed a behaviour hitherto never seen, they coordinated together in a rhythmic social ritual.

Two chimpanzees housed in a zoo in the US have sparked the question about how human dance evolved after being observed performing a duo dance-like behaviour, similar to a human conga-line.

In the paper Coupled whole-body rhythmic entrainment between two chimpanzees’published today, the 12th of December in the Journal Scientific Reports, researchers led by the University of Warwick found the levels of motoric co-ordination, synchrony and rhythm between the two female chimpanzees matched the levels shown by orchestra players performing the same musical piece.

Other species have been shown to be able to entertain by moving to the pace of a rhythmic tempo by an external stimulus and solo individuals, however this is the first time it hasn’t been triggered by nonhuman partners or signals.

Although the newly described behaviour probably represents a new form a stereotypy in captivity in this great ape species, the behaviour forces scientists interested in the evolution of human dance to consider new conditions that may have catalysed the emergence of one of human’s most exuberant and richest forms of expression.

Adriano R. Lameira, Tuomas Eerola, Andrea Ravignani. Coupled whole-body rhythmic entrainment between two chimpanzeesScientific Reports, 2019; 9 (1)

DOI: 10.1038/s41598-019-55360-y

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. Dance requires individuals to interactively synchronize their whole-body tempo to their partner’s, with near-perfect precision. This capacity is motorically-heavy, engaging multiple neural circuitries, but also dependent on an acute socio-emotional bond between partners. Hitherto, these factors helped explain why no dance forms were present amongst nonhuman primates. Critically, evidence for conjoined full-body rhythmic entrainment in great apes that could help reconstruct possible proto-stages of human dance is still lacking. Here, we report an endogenously-effected case of ritualized dance-like behaviour between two captive chimpanzees – synchronized bipedalism. We submitted video recordings to rigorous time-series analysis and circular statistics. We found that individual step tempo was within the genus’ range of “solo” bipedalism. Between-individual analyses, however, revealed that synchronisation between individuals was non-random, predictable, phase concordant, maintained with instantaneous centi-second precision and jointly regulated, with individuals also taking turns as “pace-makers”. No function was apparent besides the behaviour’s putative positive social affiliation. Our analyses show a first case of spontaneous whole-body entrainment between two ape peers, thus providing tentative empirical evidence for phylogenies of human dance. Human proto-dance, we argue, may have been rooted in mechanisms of social cohesion among small groups that might have granted stress-releasing benefits via gait-synchrony and mutual-touch. An external sound/musical beat may have been initially uninvolved. We discuss dance evolution as driven by ecologically-, socially- and/or culturally-imposed “captivity”.