Speech Linked With Bipedality By UMBC Professor

The ability to speak is both a mechanical and neurological issue. In quadrupeds, there is a one-to-one correlation between breathing pattern and stride because the lungs must be fully inflated to add rigidity to the thoracic complex (sternum, ribs and associated musculature) that absorbs forelimb impacts during running. Without such synchronization, the thorax is weak and unable to absorb the impact. When primates stood and walked on two legs, the thorax was freed of its support function during locomotion, breaking the link between breathing patterns and stride. This flexibility enabled humans to regulate breathing and ultimately, speak.

A prominent expert on laughter, Provine discovered this link while studying chimp laughter, which sounds like panting. Provine found that the pant-like laugh is a result of an inability to manipulate breathing patterns, limiting chimps to a simple inhalation-exhalation cycle.

"Humans have more flexible respiratory control, making it possible to chop an exhalation into parts, as is evident in the 'ha-ha-ha' pattern of laughter," says Provine.

He points out that humans both laugh and speak by the modulating sounds produced by an outward breath. Without respiratory control, human laughter would more closely resemble chimp laughter and speech would be impossible.

Provine's poster presentation "Stand Up and Talk," is based on his upcoming book, Laughter, to be published by Little/Brown in the spring of 2000.