Primate Facial Gestures May Be The Origins Of Human Speech

The exact origins of human speech have eluded scientists, but recent research may head us in the right direction. It seems that communicative facial gestures, such as the lip smacking that monkeys do, may have played a larger role in our speech development than the vocal primate calls.

Researchers from Princeton University and the University of Vienna used x-rays to help hone in on the nature of lip-smacking done by macaque monkeys. While lip smacking may resemble a simple opening and closing of the lips much like chewing, it is in fact much more complex, involving coordination of the lips, jaw, tongue, and the hyoid bone, which supports the larynx and tongue.

Lip smacking is a friendly gesture that occurs in face-to-face situations.

The scientists found that these movements occur at about five cycles per second, which is the same rate as human speech. Chewing, meanwhile, occurs at about 2.5 cycles per second. 

Traditional hoots and grunts made by primates were theorized to be the beginning of human speech. However, these vocalizations are innate, unlike human speech which has to be learned. The findings also show that the movements and nature of lip smacking resemble the movements made when humans alternate between vowel and consonant sounds.

Chimpanzeees can make lip buzzing noises, and orangutans can learn to whistle. These vocalizations, unlike hoots and grunts, are learned, and share characteristics with lip smacking and human speech. The origin of singing, which requires volunatry control of the larynx, is still a mystery.