Miriam Wessels/University of Portsmouth/AP
It's no laughing matter.
A new study published today in the scientific journal Current Biology argues that human emotional expressions have their origins in a shared ancestor, who roamed the earth approximately 10 million years ago. As Malcolm Ritter of the AP writes, the results provide "very strong evidence that ape and human laughter are related through evolution."
So how exactly did a group of scientists test their theory?
Well, they rounded up a group of apes – 22 in all – and then they tickled them. And then they tickled them some more. "The current work examined the acoustics of tickle-induced vocalizations from infant and juvenile orangutans, gorillas, chimpanzees, and bonobos, as well as tickle-induced laughter produced by human infants," reads the summary from the study. "Taken together, the results provide strong evidence that tickling-induced laughter is homologous in great apes and humans."
The experiment was headed by Marina Davila Ross, a scientist at the University of Portsmouth, in England, and involved staff from the Institute of Zoology in Hannover, Germany, and the Department of Psychology at Georgia State University, in the US.