Tuesday, April 16

Lip smacking and the origins of language

In a previous installment, I discussed gelada vocalizations and some new research specifically dealing with copulation calls. Thore Bergman, one of the same researchers who put together that paper, just published a short correspondence discussing a wide array of gelada vocalizations and their relationship to the evolution of human language.

This topic is been a tricky subject to approach because no primates' vocal range compares to humans'. The closest connection has been "lipsmacking", which is exactly what it sounds like: monkeys smacking their lips at each other without vocalizing. It very common among multitude of primate species.

Lipsmacking isn't a behavior that intuitively seems like it would have a connection to human language, but it turns out that the rate at which these monkeys smack their lips together is remarkably similar to the rate at which human lips open and close when they produce speech.

Gelada's take lipsmacking a step further. It turns out that they can produce a vocalization while smacking their lips together; it is called a "wobble". A as with lipsmacks, the rhythm of these wobbles is very close to the rhythm of human speech (between 3 and 8 Hz).

As I am fond of repeating, wobbles and human language are an example of convergent evolution. Baboons don't wobble. Chimps don't wobble. All of these species lipsmack. Even though the wobble is closer to language than the lipsmack, we just aren't that closely related to geladas, so the simplest explanation is that wobbles and language evolved independently from the same foundation, lipsmacking.

Have a look for yourself. Bergman provided a video in the supplement to his new publication, here.

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