Why We Laugh and Talk, But Chimps Don't
Robert Provine, professor of psychology at the University of Maryland, Baltimore, found that human laughter is different from that of our primate cousins. Chimpanzee laughter sounds like panting, with only one sound made per outward or inward breath. It's this one-to-one ratio between breath cycle and vocalisation that makes it impossible for most primates to speak. When humans began walking upright, it freed the upper body from weight-bearing functions and allowed better breath control. As a result, humans can chop an exhalation and modulate it to produce language and laughter. Chimps can have linguistic concepts, but they can't physically make the sounds of language. Because we walk upright, humans have a huge range of freedom in the sounds we make, including speech and laughter.
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