Why do we LOL? Is ROFLing an innate piece of human behavior? Does our tendency to LMAO say something about us—something that separates us from the non-kekekeing species who share our planet?

For Scienceline, William Herkewitz explores the evolutionary history of laughter, a story that shows us that maybe we’re not quite so unique as we’d like to think. It’s not just that we laugh at funny things. The roots of this behavior, scientists think, go back much further and actually play an important purpose.

Herkewitz finds that various theories abound, but that the current “best guess” says that humans laugh to tell other humans not to get too fussed over something that could otherwise be regarded as scary or dangerous.

If you’re an ancestral human, says Ramachandran, and you come across what you think is a dangerous snake but actually turns out to be a stick, you’re relieved and you laugh. “By laughing, you’re communicating: ‘All is OK,’” says Ramachandran. Ramachandran believes the “false alarm” signaling purpose of laugher explains its loud sound and explosive quality. If you want to signal something to a larger social group, they better hear it. His theory also helps explain the contagiousness of laughter — a curious quality exploited by the laugh tracks of TV sitcoms. Strangely enough, hearing the sound of laughter, on its own, is enough to elicit more laughter in others. “A signal is much more valuable if it amplifies and spreads like wildfire in the group,” says Ramachandran.

People also laugh to show pleasure, to bond with other members of the group. And in this regard, humans’ laughter isn’t special.

Our laughter, the Tommy gun staccato sound of “ha-ha-ha,” is unique in the animal kingdom. Beyond scientific anomalies like Mister Ed or Babe the pig, if you visit your local zoo you’ll be hard-pressed to find any animals making a sound you’d confuse with human laughter. But do humans, in the vast gallery of life, laugh alone? Ask Jaak Panksepp, a neuroscientist and veterinarian at the University of Washington, and he’ll tell you no. Panksepp studies laughter where you might least expect it, in lab rats. “In the mid 1990’s we found have a sound — a high-pitched chirp — that they made most often during play,” says Panksepp. “It crossed my mind it might be an ancestral form of laughter.” And Panksepp, eager to investigate, dove hands-first into his theory. He tickled his rats. What he found lead to two decades of research. “They’re just like little children when you tickle them,” says Panksepp. “They ‘love’ it.”

Dogs, too, laugh in their own way. As do primates. The work is a reminder that for all that humans are, and all the things we do, there’s actually very little that makes us special.

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