After tickling two dozen apes and several children, scientists have concluded that laughter developed long before humans did. In fact, a common ancestor of both apes and humans probably emitted the first chuckle at least 10 million years ago. The study measuring 800 vocalizations found that all subjects shared the same central and peak frequencies. Chimps and bonobos—closest to humans in the evolutionary tree—laughed in a short series, like humans, the BBC reports.
"When humans laugh, they voice stable sounds: that means the vocal folds are moving in a very regular synchronized way," said one researcher. "We found these acoustic properties also in bonobos." The findings are "fun but not all that surprising," an evolutionary anthropologist says. The real question: Does laughter mean the same thing among the different species? More tickling awaits.