Why can we laugh and talk, but no chimpanzees

Robert Provine, a psychology professor at the University of Maryland in Baltimore, found that human laughter was very different from primate laughter. Chimpanzees laugh like a cough. The monkeys make one sound on the inhale and one on the exhale. This ratio does not allow most primates to talk, laughing. When a person started walking on two legs, the upper part of his body was freed from heavy load, which allowed him to better control his breathing. As a result, people were able to interrupt the exhalation and modulate it for speech and laughter. Chimpanzees have the beginnings of speech, but these monkeys are physically unable to reproduce the sounds of speech. Walking upright allows a person to make a wide variety of sounds, to talk and laugh.