The final key observation is that laughter occurs even in other species. Specifically, it’s found in all five of the “great apes”—orangutans, gorillas, bonobos, chimpanzees, and humans—although not in any other primates, suggesting an origin in our common ancestor, 12 to 18 million years ago. This evolutionary account is corroborated by the acoustic properties of laughter. By analyzing recorded laughs from each of the great-ape species, researchers were able to reconstruct the same “family tree” of species relationships that we know from genetics. In other words, the more closely related two
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