Humans and great apes exhibit similar giggling patterns, suggesting a shared evolutionary past dating back approximately 15 million years, according to a new study.
Researchers re-examined decades-old recordings of tickled captive apes, including gorillas, orangutans, chimpanzees, and bonobos. These were compared with newly captured recordings of four young children being tickled and playing. The analysis revealed that the vocalizations, or chuckles, of both humans and great apes follow similar rhythms, with consistent timing between laughs.
"In a way, we are very similar to other great apes because we’ve been laughing in a similar way for 15 million years," said Chiara De Gregorio, a primatologist at the University of Warwick in England and an author of the study. The findings were published in the journal Communications Biology.
Laughter serves as a non-verbal communication of playful or happy emotions. While many animals can produce laughter-like sounds, their patterns do not always closely align with human laughter. For instance, tickled rats emit ultrasonic squeaks rather than human-like chuckles.
Scientists have previously studied animals' facial expressions to understand the evolution of laughter, but less attention has been paid to the acoustic properties of these sounds. Human laughter, compared to that of apes, has become more rapid and complex, with variations in sound reflecting different social contexts, ranging from a polite chuckle to a hearty guffaw.
"We are like the masters of laughter, I would say," De Gregorio noted. She suggested that these giggling evolved to suit the diverse social lives of different animals.
Brittany Florkiewicz, who studies animal communication at Lyon College and was not involved in the research, commented that the study's findings are logical and highlight the need for further investigation. She expressed interest in analyzing recordings from other animals known for playful expressions, such as dogs, horses, and cats, to gain a deeper understanding of how laughter evolved and what similarities and differences exist between humans and other species.
Studying the origins of laughter is considered a facet of understanding human communication, including the development of speech. As sounds do not fossilize, scientists rely on existing evidence to trace back the evolution of vocalizations.