As the human brain evolved, humans were able to laugh before they could speak, according to a new study.

　　But here’s the punch line: Laughter and joy are not unique to humans, the study says. Ancestral forms of play and laughter existed in other animals long before humans began cracking up.

　　"Human laughter has robust roots in our animalian past," said Jaak Panksepp, a professor of psychobiology at Bowling Green State University in Ohio. Panksepp has studied rats and found that when they "play," they often chirp—a primitive form of laughter, according to the scientist. In an article to be published tomorrow in the journal Science, he makes the argument that animal laughter is the basis for human joy.