An international team of scientists has discovered that humans and great apes have maintained the same laughter trait for around 15 million years.
The results of the study were published in the journal Communications Biology (ComBio).
To study the origins of laughter, researchers tickled four orangutans, three bonobos, two gorillas, and four chimpanzees and recorded their responses. The analysis showed that all great ape laughter has an isochronic rhythm – bursts of sound occur at roughly equal intervals.
The same rhythmic structure is characteristic of human laughter. According to the study authors, this means that this feature arose in the last common ancestor of humans and modern great apes, which lived about 15 million years ago.
"The rhythmic regularity of laughter is remarkably well preserved in great apes. This suggests that we have been laughing this way for about 15 million years," said study author Chiara De Gregorio.
However, there is one important difference between humans and other primates. Humans can vary the pace and character of their laughter depending on the situation – from a light chuckle to a loud roar or even a fake laugh. Monkeys have almost no such flexibility: their laughter remains roughly the same when they play or when they are tickled. Scientists believe that the development of the ability to control and modify laughter may have been one of the steps towards the emergence of speech. Although laughter is not a language, both phenomena are based on the subtle manipulation of sound signals.
