Human laughter may be far older than previously understood, with new research suggesting that its rhythmic foundations were inherited from a common ancestor shared with the great apes roughly 15 million years ago.
Scientists who compared laughter produced by humans, chimpanzees, bonobos, gorillas and orangutans found that all five species share a remarkably consistent rhythmic structure. The findings indicate that laughter evolved long before the emergence of modern humans and may have played an important role in the development of social communication and, eventually, language.
The study, published Monday in the journal Communications Biology, examined recordings from four chimpanzees, three bonobos, two gorillas, four orangutans and four humans. Researchers analyzed 140 laughter sequences, measuring the timing between successive vocal bursts to determine whether common patterns existed across species.
Lead author Chiara De Gregorio, a primatologist and research fellow at the University of Warwick, said the research demonstrates that human laughter retains the same fundamental evolutionary roots as the laughter of other great apes while also displaying characteristics that distinguish it from its closest relatives.
According to De Gregorio, human laughter is generally faster, more rhythmically complex and far more adaptable to different social situations than ape laughter. Although chimpanzees and bonobos produce laughter that most closely resembles that of humans because they are our nearest living relatives, people exhibit a greater degree of flexibility in modifying their vocal rhythms.
Researchers believe this increasing rhythmic complexity may reflect evolutionary changes in vocal control that eventually contributed to the emergence of spoken language.
The human evolutionary lineage separated from that of chimpanzees and bonobos approximately 7 million years ago, yet the newly identified laughter pattern appears to predate that split by millions of years. Because every species examined displayed evenly spaced intervals between laughter sounds, scientists concluded that this vocal rhythm likely existed in their last common ancestor, which is believed to have lived in East or Central Africa about 15 million years ago.
The ape recordings used in the study were collected in familiar zoo environments in Germany and Malaysia while the animals were engaged in play or gently tickled by caretakers they recognized. Human participants were also recorded in playful situations, allowing researchers to compare laughter across similar contexts.
While the shared rhythmic structure remained consistent among species, humans demonstrated an ability to adjust the pace of laughter depending on social circumstances. Researchers found little evidence that great apes altered their laughter rhythm in response to changing situations, although they noted that future studies may reveal more subtle variations.
The findings suggest that laughter has evolved gradually throughout the evolutionary history of great apes and humans rather than undergoing a sudden transformation unique to modern people.
Researchers believe the results also provide new insight into the origins of language. Increased flexibility in laughter rhythms may indicate that early human ancestors possessed more sophisticated vocal control than modern apes, creating an evolutionary stepping stone toward speech.
De Gregorio said studying laughter among humanity’s closest relatives helps scientists understand not only where language came from but also the emotional and social behaviors that define human interaction.
Laughter itself likely originated as a social signal during play, helping individuals distinguish friendly interactions from genuine aggression. During rough-and-tumble play, laughter communicates that behavior is non-threatening and reinforces positive social bonds.
Although humans have expanded laughter into a complex social tool used in humor, embarrassment, irony and countless other situations, researchers argue that its evolutionary roots remain firmly connected to play.
Scientists also note that laughter-like behaviors are not limited to great apes. Dogs, for example, produce distinctive panting vocalizations and characteristic facial expressions during play that appear to serve similar purposes by signaling friendly intentions. Comparable play-associated vocalizations have also been documented in several other mammal species, suggesting that social communication through playful sounds may be widespread across the animal kingdom.
The study adds to growing evidence that some of humanity’s most recognizable behaviors evolved gradually over millions of years and continue to reflect ancient biological traits shared with our closest evolutionary relatives.
