An orangutan named Tilda is providing scientists with fresh evidence that even early human ancestors had the ability to make speechlike vocalizations.
Tilda has learned to produce vocalizations with striking similarities to human speech, scientists report in the journal PLOS ONE. If you listen without knowing the source, "you might wonder whether or not it is a human," says Rob Shumaker, an author of the paper and vice president of the Indianapolis Zoo.
The finding could help answer a big question about our human ancestors' ability to produce speech before they developed a modern vocal tract and brain. If orangutans and other great apes can make speechlike sounds, it stands to reason that early humans could too, Shumaker says.
Tilda, who is about 50 now, was born in the wilds of Borneo, where orangutans make calls that often include sounds like kisses, squeaks and grunts. But she was captured young and has spent most of her life around people.
Eventually, Tilda learned to imitate people, says Adriano Lameira, the lead author of the paper and a founder of the Pongo Foundation, which studies orangutans and works to protect them.
Tilda waves her arms and shakes her head the way people do, Lameira says. She also reportedly smoked cigarettes before she got to the zoo (maybe by way of her prior life as an "entertainment animal," the scientists say). And Tilda whistles, something orangutans don't do in the wild.
It was the whistling that led researchers to discover Tilda's vocal skills. Lameira was part of a team studying orangutans that can whistle. But when they visited Tilda and began recording her behavior on video, she did something different.
"We were waiting for the whistles and suddenly she started to do these bizarre calls," Lameira says. It was unlike anything he'd ever heard from an orangutan, in the wild or in captivity. He says the rhythmic strings of consonants and vowels were like a cartoon approximation of a person speaking.
"She was producing these calls repeatedly and really quick," he says. "And this is also what we observe in humans while we are speaking to each other. We are, on average, producing five consonants and five vowels per second."
An analysis of Tilda's "faux speech" later showed she was matching that frequency precisely. "This was really what astonished us," Lameira says.
The finding goes against earlier thinking that great ape vocalizations are reflexive and very limited, Shumaker says. "What we have to do is discard this old idea that apes are simply incapable of doing anything remotely similar to human speech production," he says. "I think what we're finding is there's a lot more flexibility than we realized."
The research on orangutan whistling showed that great apes could learn to make new sounds, Shumaker says. And the study of Tilda suggests they also can learn new vocal patterns. Taken together, he says, the research hints that great apes could be a model for the development of speech in early humans.
It will take more animals with Tilda's abilities to confirm the hypothesis, Shumaker says. But, he adds, "I think as we start looking, we'll find out Tilda is not the only orangutan like this."
RENEE MONTAGNE, HOST:
An orangutan named Tilda is providing scientists with some fresh clues about the origins of human speech. NPR's Jon Hamilton reports on a great ape who can sound remarkably human.
JON HAMILTON, BYLINE: Tilda was born in the wilds of Borneo, where orangutan calls often sound like this.
(SOUNDBITE OF ORANGUTAN CALL)
HAMILTON: For decades though, Tilda has lived around people. And one day, scientists noticed that she was making vocalizations like this.
(SOUNDBITE OF ORANGUTAN CALL)
HAMILTON: Adriano Lameira, a researcher at the University of Amsterdam, says it was unlike anything he'd ever heard from an orangutan. He says Tilda's fast-paced stream of consonants and vowels was like a cartoon approximation of a person speaking.
ADRIANO LAMEIRA: She 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.
HAMILTON: Lameira says an analysis done later found that Tilda had matched that pace precisely.
LAMEIRA: This was really what astonished us.
HAMILTON: The finding was an accident of sorts. Lameira had been shooting video of Tilda as part of a study of orangutans that can whistle.
LAMEIRA: Like (whistling).
HAMILTON: Another behavior not seen in the wild. Back in 2008, Lameira had co-authored a paper about one orangutan who learned to whistle the way her caretakers did. That animal, Bonnie, lives at the Smithsonian's National Zoo in Washington. Lameira says when the paper came out, his inbox began to fill up.
LAMEIRA: We started to get emails from other caretakers saying, oh, but my orangutan can whistle much better than yours.
HAMILTON: And Lameira says one of those emails lead to Tilda.
LAMEIRA: She's an old lady. She's around 50 years old. She's in the Cologne Zoo in Germany.
HAMILTON: Tilda had been captured in Borneo when she was just 2. She'd spent much of her life as a privately-owned entertainment animal. Along the way, Tilda learned to imitate people. She waves her arms and shakes her head the way we do. She also reportedly smoked cigarettes before she got to the zoo. And she whistles. So Lameira and his team went to the Cologne Zoo to film Tilda in action.
LAMEIRA: We got there, and we were waiting for the whistles. And suddenly she started to do these bizarre calls.
HAMILTON: Which the team labeled faux speech. Rob Shumaker is an orangutan researcher and a vice president at the Indianapolis Zoo. He's also a co-author of the new paper on Tilda.
ROB SHUMAKER: The results of this study clearly give us some more information about the origins of human speech.
HAMILTON: One big question has been how much speech our human ancestors were capable of before they developed a modern vocal tract and brain. Scientists agree that if orangutans and other apes could make speech-like sounds, early humans probably could, too. But there's been a debate about whether great apes have the ability to consciously control their vocalizations. Shumaker says orangutan whistling showed that great apes can learn to make new sounds. And he says Tilda's faux speech shows that at least one great ape is able to learn new rhythms and patterns.
SHUMAKER: 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.
HAMILTON: Shumaker says it will take more examples to confirm that great apes can mimic human speech patterns.
SHUMAKER: I think as we start looking, we'll find out Tilda's not the only orangutan like this.
HAMILTON: The new research appears in the journal PLOS ONE. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.