Short Wave - If Monkeys Could Talk...

Episode Date: July 1, 2022

... Could a monkey host this podcast?Aaron Scott and Resident Neuroscience Nerd Jon Hamilton discuss the vocal capabilities of our primate relatives. From syllables and consonants to rhythm and pitch, certain monkeys and apes have more of the tools needed for speech than was once thought. Now scientists are looking to them for insights into the origins of human speech. What animal should we study next? Email the show at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hello, Shortwave. Aaron Scott here. Today we're going to get a little meta. We are going to talk about talking, human speech, that is, with NPR science correspondent John Hamilton. Hey there, John. Hey, Aaron. So I've got a question for you.

Okay. Have you ever wondered what it would sound like if this podcast were hosted by a monkey? I mean, our fact checker would point out that it is hosted by a monkey. primate, but I cannot say that that particular question has crossed my mind. No. Well, fortunately for you, I have. I'm fortunate. And I'm pretty sure it would sound something like this. That is like a kindergarten classroom. And I mean, I got to say that they've got energy. What sort of monkeys that we're listening to? I know. You picture a bunch of kids banging on the table,

right? But in fact, that is a marmoset. In the monkey world, they are considered vocal prodigies, masters of simian elocution, if you will. So a marmoset is definitely the monkey I would pick to replace you. Uh, thank you. I think. But got to say, I think there's one problem, as far as I understand, marmosets can't actually speak. It's going to be a short podcast. They don't speak, but, you know, maybe they could. I have been talking to scientists who think certain great apes and monkeys, including marmosets, are capable of producing something like human speech. Okay.

And the fact that they're talking about that idea at all represents a really big change in the field. You know, for a long time, scientists thought monkeys and apes simply lacked the vocal apparatus needed to produce speech. And more recently, the argument has been that these animals lack the brain circuits that make human speech possible. But, you know, both of these ideas are being challenged by some pretty persuasive new studies. And this is part of a big scientific debate about how and when humans first started speaking. So today on the show, what monkeys and apes can tell us about the origins of human speech?

And why we humans may not be as special as we once thought we were. I'm John Hamilton. And I'm Aaron Scott, and you are listening to Shortwave, the Daily Science Podcast from NPR. Okay, John, so tell me about this debate over the origin of human speech. Right. So one camp has been arguing that early humans made some sort of great evolutionary leap forward. something that made speech possible, like really suddenly. And this created a huge gap between us and other species. The other camp says humans simply improved on vocal abilities that were already present in other species. And so we're really not that special. Of course, there aren't

any early humans around to settle this debate. And, you know, fossils can only tell you so much. But what you can study is the vocal abilities of present-day monkeys and apes. And that gives you some sense of what evolution was doing millions of years ago. So that's why we're talking about them. Fair, fair. And you mentioned that there are studies showing that monkeys and apes do have some surprising vocal abilities. Let's start with an example. Yeah, let me tell you about a study that compared two species of monkeys.

One is the marmoset. That's the monkey we just heard up there. The other is the macaque. So marmosets are small and found primarily in South America. Macacques are larger and come from Africa and Asia. I talked about these monkeys with a scientist at the University of Pittsburgh. Her name is Christina Cerkovich, and she told me the two species are really different when it comes to vocalizing. So macaques, for example, do make calls, but they're pretty limited.

They don't really change the structure of their vocalizations. They don't change the pitch. They don't change the internal timing. A lot of times their calls don't have syllables. John, that sounds like a very much. very unhappy toddler. Yeah, it does. And that makes sense because the macaques usually are just expressing emotion when they may make vocalizations. I hear that. Cerkovich told me that marmoset monkeys are on a totally different level, though. These guys have wonderful control over their vocalization.

They'll change the pitch, get louder because somebody's far away. They'll change the timing so that if you keep artificially cutting them off, they'll wait for the noise to go away. I love it. Like, humans, they don't want to be interrupted. Exactly. So, John, what is it about marmosets that makes their vocalization so complex? Well, that's what Cerkovich and some of her colleagues wanted to note. They knew it couldn't be the vocal tract, because that's pretty much the same in marmosets and macaques. So they started comparing the animal's brains. You know, specifically, they looked at these two areas in the brain that control one tiny muscle in the larynx. It's a muscle that changes the pitch of a sound. So it sounds like the idea is that

that if these little brain structures are really different, that might explain why one monkey is a better talker than the other. And do they find any sort of big difference then? Well, that is what I asked another scientist on the team. His name is Peter Strick. And of course, being a scientist, he wanted to answer my question by showing me a slide. This one of two brains side by side. Of course. You can see this ventral area is greatly expanded in the marmoset. And this other area, the supplementary motor area, also has much greater output in the marmoset. And we believe that these two areas are really key in enabling marmoset complex vocalization. So, yes, these monkey brains have some major differences.

And here's the cool thing. Those areas don't exist in rodents, but they do in humans. And in our brains, these areas are enlarged even more than they are in a marmoset. So that kind of supports the idea that our brains just got better at something a monkey brain was already doing. Okay, I like that. I'll buy that a monkey brain is wired for something like speech. But then what about their voice box and the actual ability to make those sounds?

Yeah, so another group of scientists actually pretty much answered that question several years ago. They made a computer model of a monkey's vocal tract. And then they simulated what it would sound like if a monkey tried to say phrases like, oh, I don't know, will you marry me? Will you marry me? Oh, John, I think I need to hear that again. Will you marry me? That's supposed to be a yes or no answer, I think.

That is eerie. It doesn't fill me with a lot of romance, I have to admit, but it's just incredible how human they sound. Does anyone ever actually taught a monkey to speak? Not that I'm aware of, but let me tell you about a couple of orangutans who have become pretty good talkers. Arangetans, of course, are great apes, just like chimpanzees and gorillas and bonobos. So they are one of our closest living relatives. The first orangutan I want to tell you about is named Tilda. She was born in the wild, but she spent most of her life in a zoo in Germany.

So she was around people all the time. And eventually, her caretakers noticed that she was making sounds in a rhythm that was more like human speech than an orangutan call. So for comparison, here's what an orangutan sounds like in the wilds of Borneo. And here's Tilda doing her version of human conversation. Wow, John. It reminds me of the noise that the adults make in the Peanuts cartoon. But how do we know that what she's doing is trying to imitate the rhythm of human speech and not something else? Yeah, that's the question a team of scientists had. So they used a computer to analyze the sounds Tilda was making. Then they compared that cadence to human speech. I talked to a scientist named Adriano Lamira about it. He's at the University of Warwick in the UK. And he's a He says the computer found that Tilda was producing about five vowels and five consonants each second. He was producing these calls repeatedly and really quick.

And this is also what we observe in humans while we're speaking to each other. We are on average producing five consonants and five vowels per second. Okay. So, John, that is one element of human speech that researchers are found in orangutans. Have they found anything else? They have. A few years ago, I went to the Indianapolis Zoo to meet an orangutan named Rocky. And I'd been talking to the zoo's president. He's an evolutionary biologist named Rob Shoemaker. And he told me that Rocky came to the zoo after a career in showbiz. A number of years ago, he was certainly the most visible orangutan in entertainment at the time, TV commercials, things like that. Hey, boss, do we have Aflac? No, we have...

So show business is literally going to the apes. Okay, thank you. Yeah, it's not really a place that orangutan should be, but what it meant was that Rocky had spent more time socializing with people than he had with other orangutans. He learned to make these human-like sounds when he was interacting with people, especially Rob. I actually recourse at one of those interactions when I was at the zoo.

When we have special visitors like today, we do really big treats. Oh, that's Rocky. Rocky trying to get my attention to come over and hold on, bud. Hold on. Hold on. What? John, did, did we just hear Rocky say what? Sure sounded like it to me. I mean, clearly this orangutan has learned to make sounds that orangutans don't make in the wild. And that is a big step toward speech. So Rocky also can control the pitches. of his voice, and that is another key element of speech. Here's a recording of him working with a scientist. Right?

So, Rob told me that what scientists have learned from Rocky and Tilda is that we humans aren't that different from some other species. What we have to do is discard this old idea that apes are simply incapable of doing anything remotely similar to human speech production. I think what we're finding is there's a lot more flexibility than we realized. John, how does all this research on monkeys and apes fit him with what scientists know about we humans? I talked about that with a scientist named Eddie Chang at the University of California, San Francisco.

He has spent a lot of his career studying what goes on in the brain when we speak. He's even built this device that decodes the speech signals of a person's brain. And here's what Eddie told me. We've made a lot of progress in the last 10 years understanding the electrical activity that gives rise to the coordinated movements of our lips, our jaw, the tongue, and the larynx. So it's the coordination of all of these areas together that allow us to speak fluently. And what Eddie said after that was that it's pretty clear now that many of the speech circuits found in people can also be found in other species. That suggests evolution has been refining these circuits for like millions of years.

It also suggests humans didn't make any great leap forward. we just kept taking these tiny evolutionary steps that eventually allowed us to have the conversation we're having now. So, John, it's true. With a little bit of training, an Abe could host an episode of Shortwave. I look forward to that day. I think Rocky might be available. Get his agent on the phone. Thanks for talking with us, John.

Anytime. This episode was produced by Margaret Serino with help from Burley McCoy. It was edited by Gabriel Spitzer. Rachel Spitzer, Rachel Carlson Check the Facts. and the audio engineer was Patrick Murray. Giselle Grayson is our senior supervising editor. Beth Donovan is our senior director, and Anya Grumman is our senior vice president of programming.

I'm Aaron Scott. Thanks for listening to Shortwave from NPR. Maybe there's some host potential there? I don't know. Depends on what kind of show. Yep. It might be more of an AM radio kind of vibe.