Rhythm is a Biped: Your Mother Walked so You Could Talk

| By Georgina Holmes

Music has often been crowned “The Universal Language of Mankind”. Its unifying feature being rhythm, which – irrespective of native language – can be understood as well as the expressions of a face, evoking similar emotions in even the most disparate of cultures. Dance and song can connect people perhaps just as effectively as verbal communication. Music’s shared bonding efficacy with language makes sense in light of new findings on their shared evolutionary origins; beginning in the rhythms of the womb, bipedal footsteps didn’t just set the stage for dance, drums, and John Bonham, but also for the evolution of speech itself.

Unlike the irregular gaits of quadruped primates, upright walking provided a metronome for the developing fetus as the predictable thud of the mother’s footsteps created a steady auditory input – priming the brain for rhythmic entrainment aka synchronising to rhythms. Known as the Prenatal Rhythmic Experience (PRE) hypothesis, it was in the rhythm of the bipedal walk that we gained our ability to synchronise with external rhythm. In fact, typical walking speed is around 120 beats per minute - a tempo that gives most hit songs their danceability.

But rhythm isn’t just for the dancer – it has transformed communication. A recent study by Matz Larsson and Dean Falk, published in Current Anthropology, purports that bipedalism shaped human linguistic capabilities in early hominin fetuses. Whilst many primate infants cling to their mothers fur, in the shift to upright walking feet began to lose their grasping capacities and limitations in physical contact between mother and child grew. Infants separated from caregivers – even by short distances – produce gestural and vocals signals such as crying to communicate their needs. In response, vocal interaction becomes an essential for bonding. Cue motherese: a rhythmically exaggerated speech that caregivers instinctively use to communicate with infants that remains a universal across cultures.

This became a training ground for linguistics, entraining the motor capacities for the physical production of pitch, vocalisation rate, and communication cues. Entrainment essentially arises through neural oscillations that are stimulated by rhythmic sounds, creating the ability for motor control of such vocalisations (and movements in the case of dance) to align with anticipated ‘events’ or beats. In light of this new information, it’s clear that we evolved the ability to talk from the neurological substrates that bipedalism provided us with and that these changes were later exapted for dancing.

Stepping forward, this information poses unique questions for further research. Could there be a correlation between variation in gait speed, cadence, and step length and the diversity of rhythmic structures observed in different languages? With studies that observe subtle differences in the walking patterns of Japanese children compared with children speaking entirely different languages in other countries, these questions have plausible room to be explored. Could children born from mothers who are unable to walk, especially during pregnancy, have altered rhythmic entrainment? Could the prevalent use of push-chairs in the modern day hinder or transform early life auditory-motor experiences? And on this, is the intrauterine experience more important than the experience of a baby outside the womb? These findings might also be beneficially integrated into public health, with the potential for rhythmic therapy to help those with movement or speech disorders.

Whilst you’ll be unlikely to find any non-human primates with rhythmic perception, maybe Robbie William’s biopic isn’t far from impossible as two chimpanzees in the St. Louis Zoo have regularly been seen walking bipedally in a synchronised conga – revealing the dormant potential that links the bipedal gait to rhythmic movement. So next time your legs are getting tired from dancing along at a concert, you have them to thank for the music – and your ability to tell the person in front of you to move their damn head.