Great ape laughter reveals how human vocal control evolved

By Tarun Sai LomteReviewed by Susha Cheriyedath, M.Sc.Jun 28 2026

From tickling apes to laughing children, a new study traces how the rhythm of laughter may reveal the deep evolutionary roots of human speech.

Study: Rhythm and timing in laughter reveal that human vocal plasticity falls on a hominid continuum. Image Credit: Andrea Izzotti / Shutterstock

In a recent study published in the journal Communications Biology, researchers conducted a comparative analysis of laughter across representatives of all major living great ape lineages, including humans.

Because sounds do not fossilize, tracing the vocal origins of language, speech, and song remains difficult. While major Hominid family branches have distinct call repertoires, one vocalization, laughter, has been conserved across species. Given the inherently cyclic and repetitive nature of laughter in humans and great apes, variations in its temporal organization and structure may offer a means to study evolutionary changes in vocal-respiratory coordination across hominids.

About the study

In the present study, researchers compared laughter across orangutans, gorillas, bonobos, chimpanzees, and humans. First, audio recordings of laughter bursts were collected from four non-human primate species and humans. Non-human primates included two gorillas, four orangutans, four chimpanzees, and three bonobos. Human participants were four children, aged 6 months to 7 years, who were recorded during natural, playful interactions with their mothers. Because the dataset included few individuals per taxon, the findings are strongest as phylogenetic and behavioral-context patterns rather than definitive species-level estimates.

Non-human ape recordings, collected between 2004 and 2006 and mostly in ex situ settings, were obtained during controlled interactions with familiar humans, who elicited both play and tickle-induced vocalizations. Audio recordings were resampled to 22 kHz, and a high-pass filter was applied to reduce electrical noise interference. Recordings with a signal-to-noise difference lower than two decibels were excluded. The duration and starting point of each call were annotated.

A call was a continuous sound element with no sound gap. Consecutive calls with less than eight milliseconds of interval or the same acoustic mode belonged to the same bout. Two bouts with less than one-second intervals belonged to the same series. This study selected bouts with at least three calls, yielding 140 bouts, including 42 from bonobos, 34 from gorillas, 35 from chimpanzees, 16 from orangutans, and 13 from humans.

The duration of the intervals between the start times of calls in the same bout was calculated, with these intervals serving as a proxy for laughter timing. Next, linear mixed-effects models evaluated how tempo varied with phylogenetic distance. Researchers also estimated rhythm ratios, which compare successive timing intervals, to evaluate the rhythmic structure of laughter. Generalized linear mixed models were used to analyze these ratios and test whether laughter was isochronous or variable.

Findings

The researchers found that laughter across the sampled great apes, including humans, showed isochrony, meaning it followed a regular timing between vocal bursts. Moreover, the authors interpreted this pattern as suggesting that the isochronous structure of laughter may have been present in, or developed before, the last common ancestor of the great apes, around 15 million years ago. Notably, isochrony was contingent on the behavioral context of laughter: play laughter significantly deviated from regularity, while tickling laughter showed high regularity.

In addition, the pace of laughter was inferred to accelerate along the hominid phylogenetic sequence; tickling laughter captured this acceleration better than play laughter. Notably, only humans exhibited context-dependent tempo modulation, producing faster laughter in response to tickling than to play. Non-human great apes did not exhibit this context-sensitive shift.

Further, there was a gradual transition toward greater variability in laughter timing, with humans showing the highest variability. There was a reduction in this variability with increasing phylogenetic distance from humans, highlighting a gradual evolutionary trend in vocal flexibility within Hominids. However, the authors noted that the number of individuals per species was limited, meaning larger samples will be needed to refine species-level estimates of variability.

A Probability density function of rhythm ratios (r_k) in the two behavioral contexts (play, in yellow, and tickling in green) derived from 140 laughter bouts across 17 individuals. White lines highlight on‑integer (0.440 < r_k < 0.555, lighter shade) and off‑integer (0.400 <r_k < 0.440 and 0.555 < r_k < 0.600, darker shade) ratio ranges. *Denotes p < 0.05, indicating a statistically significant correspondence between the empirical distribution and a small-integer rhythmic ratio category. B Variation in laughter tempo across species. Each dot represents an individual observation; color indicates phylogenetic distance (in million years ago, MYA). Each square contains an image of the corresponding species, with a matching dot color for intuitive reference. Credits to M. E. Hardus, M. Davila-Ross, E. Demuru. C Variation in laughter tempo across behavioral contexts (play, in yellow, and tickling in green). *Denotes p < 0.05. Sample sizes: n = 4 biologically independent animals for orangutans, n = 2 for gorillas, n = 3 for bonobos, n = 4 for chimpanzees, and n = 4 children.

Conclusions

Taken together, the results provide evidence for a transition toward more variable, context-sensitive, and faster rhythms in humans, which may reflect evolutionary changes in vocal control capacities relevant to the later emergence of language and speech. By illustrating both derived and conserved rhythmic features of laughter, the findings map an evolutionary pathway toward greater vocal flexibility in a behavior that has been conserved for millions of years.

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