The roots of human laughter may stretch back at least 15 million years, with a rhythmic pattern shared by humans and great apes long before language emerged, according to a new study.
Researchers at the University of Warwick analyzed 140 recordings of laughter from humans, chimpanzees, bonobos, gorillas and orangutans, finding that all five species produce laughter with evenly timed intervals between successive sounds.
Published in the journal Communications Biology, the study suggests the rhythmic structure of laughter was already present in the last common ancestor of modern humans and the great apes and has remained largely unchanged through millions of years of evolution.
While the underlying rhythm appears to have been conserved, human laughter has become faster, more varied and more flexible than that of other great apes, the researchers found.
Unlike other apes, humans can consciously adjust their laughter to suit different social situations, such as expressing politeness, easing tension or signaling shared amusement, while retaining the same basic rhythmic pattern.
Lead author Chiara De Gregorio said laughter offers a rare window into the evolution of human communication because, unlike speech, it is shared by all living great apes.
"Speech leaves no fossils, and complex language exists only in our own species," De Gregorio said. "By comparing how different species laugh, we can see that a basic rhythmic structure has remained unchanged since our last common ancestor."
Co-author Adriano Lameira said the findings challenge the idea that humans developed advanced vocal control suddenly.
Instead, he said, laughter points to a gradual evolution of vocal abilities over millions of years, suggesting the foundations of speech were built through incremental changes shared across the great ape lineage.
