Monkey Calls Could Offer Clues For Origin Of Human Speech

Apr 10, 2013
Originally published on April 9, 2013 7:34 pm



This is not the sound of the ALL THINGS CONSIDERED staff morning meeting.


BLOCK: It's not Justin Timberlake doing his vocal warm-up. And it's not a celebration of hedge fund managers.


BLOCK: It is the sound of the wild gelada monkey. And why are we bringing you the sound of the wild gelada monkey? Well, because a new study finds the vocalization of these monkeys could tell us something about the beginning of human speech.

Evolutionary biologist Thore Bergman has spent a lot of time listening to the geladas in the highlands of Ethiopia. He's a professor at the University of Michigan, and he headed up the study. Welcome to the program.

DR. THORE BERGMAN: Thanks. Good to be here.

BLOCK: And the sound that we just heard, the sound we're talking about is called a wobble. Why don't you describe what the monkeys are doing?

BERGMAN: So they're vocalizing. They're producing sort of a steady hum of sound, but they're also moving their mouth very quickly, sort of rapidly opening and closing their mouths. And that produces the kind of undulation you hear in the sound.


BLOCK: There's a lot going there. What are you listening for as you listen to these monkeys?

BERGMAN: So when they're making this wobble call, the undulating one, we're listening for the interval between the pulses of loud sound and the quiet sounds that come in between.

BLOCK: Sort of the rhythm of what they're doing.


BLOCK: And what does that tell you as you listen to it? What do you conclude from that?

BERGMAN: So, well, it turns out that the rhythm has a same spacing pattern as speech does.

BLOCK: What are the gelada monkeys doing that other nonhuman primates don't do, because I thought they all communicate vocally in some way?

BERGMAN: Yeah. They definitely do. And vocalizations are very important for most primates. But the kind of puzzle has been - if you're thinking about where language came from - is that most primate vocalizations are quite simple and flat, sort of, monosyllabic grunts. And so if you look at what humans do when we communicate, it's nothing like what primates do. So we make these long strings of really complicated sounds with ups and downs and loud parts and high parts.

So people started to actually look elsewhere for possible precursors to speech. And one thing they've been looking at recently is this facial movement that monkeys do called lip-smacking. So this is a gesture that they perform in kind of friendly interactions between individuals. And the reason this behavior has become interesting is that the rhythm and the movement of the mouth is quite similar to human speech.

BLOCK: Hmm. Was this research that you've been doing, did it start because you were out among the monkeys watching them and thinking, they really look - if I look at them and listen to them, they sound like they're talking.

BERGMAN: Well, yeah, that's something we noticed right away when we first started studying the geladas, we'd - I had worked for years with baboons and other monkeys. So, you know, one of the first days we're out with the geladas, we got this sensation that there are people talking around us. So you'd be kind of looking over your shoulder to see who was talking to you, but there would just be a monkey behind you. So...


BLOCK: And no way of knowing of what they were trying to tell you, I suppose?

BERGMAN: No. We couldn't answer them back. But we sort of were struck by the strange sensation that we hadn't had working with other monkeys.

BLOCK: Well, Thore Bergman, thanks so much for talking to us.

BERGMAN: Thank you very much.

BLOCK: Thore Bergman is assistant professor at the University of Michigan. We were talking about the speech patterns of wild gelada monkeys. Transcript provided by NPR, Copyright NPR.