Scientists studying bonobos, one of humanity’s closest living relatives, have uncovered surprising clues about how rhythm and communication may have evolved.
By analyzing the timing of movements during sexual behavior, researchers hope to better understand the early building blocks of human traits such as language, music, and social interaction.
The international research team, led by scientists from the University of Pisa and involving experts from several countries, examined detailed video recordings of bonobos living in zoos.
The videos were analyzed frame by frame to measure how quickly the animals moved and how their facial expressions interacted with their behavior.
Their findings were published in the journal Evolution and Human Behavior.
Bonobos are especially interesting to scientists because they share a close evolutionary relationship with humans and chimpanzees.
Unlike chimpanzees, bonobos live in matriarchal societies where social bonds are often maintained through sexual behavior. This makes them a valuable species for studying the links between social interaction, communication, and emotion.
The researchers focused on repetitive movements during sex and on facial expressions such as the “silent bared-teeth display,” which looks similar to a grin.
One key concept in the study was “rapid facial mimicry,” a phenomenon where one animal instantly copies another’s expression. In bonobos, this imitation can happen almost immediately, suggesting a high level of synchronization between partners.
The analysis revealed that the tempo of movements during sex was remarkably fast, averaging about seven movements per second. Surprisingly, this rhythm did not speed up when one bonobo smiled or when the partner copied the expression.
However, scientists noticed a significant slowdown shortly after the rapid mimicry ended. This pattern suggests that facial expressions may not control the rhythm directly but could be linked to other internal processes, possibly related to physical or emotional changes.
Although the researchers cannot confirm exactly what causes the slowdown, the consistent pattern hints that deeper biological mechanisms may be involved. Observational data alone cannot determine whether the behavior reflects conscious communication or automatic reflexes, but the findings raise intriguing questions about how animals coordinate actions and emotions.
The study is part of a broader effort to trace the origins of rhythm and communication across species. By comparing bonobos with humans and other animals, scientists hope to identify which aspects of communication are uniquely human and which have ancient evolutionary roots. Rhythm, tempo, and coordinated movement are fundamental to music and speech, so understanding how these abilities appear in other species could shed light on how they developed in humans.
Researchers emphasize that the work relied on careful data analysis rather than artificial intelligence. Precise measurement of timing and patterns was essential for revealing these subtle behaviors.
The findings suggest that the roots of human communication may extend deeper into our evolutionary past than previously thought. Even behaviors that seem uniquely human, like music and language, may have begun with simple rhythmic interactions among our distant relatives.
