Right now, in a high-security research lab at Northwestern University's Falk Center for Molecular Therapeutics, scientists are tickling rats. Their goal? To develop a pharmaceutical-grade happiness pill. But their efforts might also produce some of the best evidence yet that humor isn't something experienced exclusively by human beings.
Scientists believe human laughter evolved from the distinctive panting emitted by our great-ape relatives during rough and tumble play; that panting functions as a signal that the play is all in good fun and nobody's about to tear anybody else's throat out. In a clever bit of scientific detective work, psychologist Marina Davila-Ross of the University of Portsmouth in the United Kingdom analyzed digital recordings of tickle-induced panting from chimps, bonobos, gorillas, and orangutans, as well as human laughter, and found the vocal similarities between the species matched their evolutionary relationships. Chimps and bonobos, our closest relatives, boast the most laughter-like kind of panting, while the noises of gorillas, further down our family tree, sound less like laughing. And orangutans, our truly distant cousins, pant in a most primitive way.
Nonhuman primates don't just laugh — there's evidence they can crack their own jokes. Koko, a gorilla in Woodside, Calif., who has learned more than 2,000 words and 1,000 American Sign Language signs, has been known to play with different meanings of the same word. When she was asked, "What can you think of that's hard?" the gorilla signed, "rock" and "work." She also once tied her trainer's shoelaces together and signed, "chase."
But what about other members of the animal kingdom — do they have funny bones? Marc Bekoff, University of Colorado-Boulder professor of ecology and evolutionary biology and author of "The Emotional Lives of Animals," believes they do. In fact, he thinks we're on the cusp of discovering that many animals have a sense of humor, maybe even all mammals. The idea that animals can appreciate comedy isn't as far-fetched as it sounds, considering some of the other groundbreaking discoveries scientists like Bekoff are making about animal behavior: They have found dogs that understand unfairness, spiders that display different temperaments, and bees that can be trained to be pessimistic.