Laughter is a universal language, but it may also be the evolutionary beginnings of language. As laughter isn’t just an act humans around the world cherish but a non-linguistic vocal expression shared by all living great apes, it offers a rare opportunity to trace the origins of vocal control that eventually led to speech and different languages in humans.
To understand how laughter has evolved over millions of years, researchers at the University of Warwick recorded and compared laughter in orangutans, gorillas, bonobos, chimpanzees, and humans. Described in their paper published in Communications Biology, they identified the same rhythmic pattern across all species, which led scientists to suggest that this form of vocal control, while laughing, was already present in our last shared ancestor 15 million years ago.
“By comparing how different species laugh, we can see that a basic rhythmic structure has remained unchanged since our last common ancestor. That's extraordinary,” said first study author Chiara De Gregorio, researcher with the Department of Psychology at the University of Warwick, in a press statement.
Read more: What Is the Origin Story of Language? Our Ancient Ancestors May Have Developed Communication Rapidly
Spontaneous Laughter Across Species Has the Same Rhythm
In their study, the researchers aimed to record spontaneous laughter, and because most of the participants weren’t human, or were simply too young (animals and humans were six months to seven years old), cracking a joke wouldn’t do the job.
Instead, the team used playful interactions, such as rough-and-tumble play or tickling, and recorded the specimens' bursts of laughter in their home environments, where they would feel safe and relaxed.
The 140 laughter sequences the team collected were analyzed for rhythmic structure and intervals between laughs, rather than focusing on pitch or intensity. One result was that the basic rhythm remained constant across species, while human laughter stood out for its speed, variability, and adaptability to context, all hallmarks of speech.
Human Laughter Is Layered and Depends on Context
Laughter is an undeniably important part of human communication and, therefore, highly complex. Spontaneous laughter, while probably the most enjoyable, exists alongside voluntary laughter, which is coordinated and adapted to certain social situations, such as timed laughter in conversation or nervous laughter after an uncomfortable situation. Although marked by the same rhythm, the latter forms are consciously controlled with a very specific goal, like communicating one’s emotions or intentions.
Looking at the origins of laughter in our relatives, with whom we share a direct ancestor 15 million years ago, this research hints at a gradual shift during the evolution of apes. They may have developed more control over their vocalizations to convey meaning, an important clue to how speech emerged.
“Speech leaves no fossils, and complex language exists only in our own species. But we've found a 15-million-year-old clue in an unexpected place: our laughter. Unlike speech, laughter is shared by all living great apes,” said De Gregorio.
Laughter as a Starting Point to Understand the Development of Speech
Although fossils can show when our ancestors developed the necessary anatomy required for speech, experts still struggle to pinpoint when they started using it that way.
“It is impossible to assess the precursor forms of language directly from our extinct ancestors,” explained study co-author Adriano Lameria, associate professor at the Department of Psychology, in the release. However, the evolutionarily older ability to laugh, still shared by all remaining great apes, offers a unique insight into how vocalization has changed throughout hominid evolution.
“Contrary to the classic notion that the first humans suddenly acquired vocal control capacities remarkably different from their predecessors, laughter evolution tells us that humans lie on a continuum, a prolongation of vocal control capacities that were already being cumulatively honed for 15 million years,” he concluded.
Read more: Human Language May Have Started With Just Two Words
Article Sources
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- This article references information from a study published in Communications Biology: Rhythm and timing in laughter reveal that human vocal plasticity falls on a hominid continuum
