With one possible exception. A group of wild monkeys from the Ethiopian highlands called geladas, which are closely related to baboons, make gutteral babbling noises that sound eerily human-like. And they do it while smacking their lips together. The combination of lip smacking and vocal sounds is called a "wobble." A study in this week's issue of the journal Current Biology analyzed the rhythm of the wobble and found that it closely matched that of human speech.

Geladas are found only in Ethiopia, in a national wilderness where steep, jagged cliffs surround high-altitude grasslands. (They sleep on the cliffs and feed in the grasslands.)Thore Bergman, the study's lead author, spends a month or two every year in theSimien Mountains National Park there studying the animals.

Lip smacking is a common animal behavior. Bergman describes it as "a rapid opening and closing of the lips." There are different styles, he says. Some animals move their tongues in and out too.

But male geladas are the only documented case of primates that make noise while they lip smack. That's the "wobble." Bergman was interested in whether the wobble contained a speech-like rhythm.