Introduction: Sorry, I Can't Help It, It's in my Ape DNA

Common sense dictates that laughter is synonymous with comedy. And, of course, a good joke, or a good SNLskit might cause us to double over with laughter. However, we actually laugh for a whole lot of reasons, and for things that are not funny in the least. Aristotle erroneously posited that, “mankind alone is ticklish both because of the thinness of his skin and because he is the only one of the animals that laughs.” Other primates laugh, other mammals laugh—though the vocalization of non-human animals is different. Laughter is effectively hardwired into the human experience. Individuals that suffer from hemiparalysis, for example, leave neural pathways intact “between the brain and face. When asked to grin, these patients produce crooked smiles—only one side of their face responds. However,” as neurobiologist and psychologist Robert Provine observes, “they produce a normal, symmetrical smile if tickled or amused by a joke—the ongoing social stimuli activate intact neuronal pathways that are beyond conscious control.” Provine suggests that with hemiparalysis “we glimpse the otherwise invisible hand of the ancient neurological puppeteer that controls spontaneous laughter and smiling.” Provine points to our ancient biological heritage, where, just as we can observe in contemporary great apes, laughter signals play—signaling between sparring parties, and the larger community, “we’re just playing.” Smiling and laughing are an important part of nonlinguistic communication.

Laughter has a social function, and as cited above, is deeply rooted in our primate ancestry. It is not an accident that we are inclined to erupt in vocalized laughter when in a group, as compared to when we might be alone. Like yawning, laughter can be strangely contagious. In 1962, for example, at a girl's boarding school in Kashasha Tanzania students broke out in uncontrollable fits of laughter—one girl apparently broke out in spontaneous laughter, and this initiated a chain reaction. The laughter soon spread, infecting others in the town as well. “In one village,” as recounted by Jad Abumrad of RadioLab, “217 people start[ed] to laugh, and cry. A second boarding school … [had] to shut down, and no one knows why.” Whatever the reason—and it does not appear that a definitive reason was determined in the Kashasha case— laughter can be quite contagious.