The ability to speak, to learn languages: It is one of the most–if not the most–defining of human characteristics.
But the whys and hows of how it evolved is a dilemma that continues to fascinate scientists, and one which composes an important part of Associate Professor Michael Wilson’s work in the Department of Anthropology.
“Language is really the central, unsolved puzzle in human evolution. Nobody has a good explanation for why we have language,” he says. “It’s really anomalous. There’s no other species on the planet that has developed language.”
Wilson, a biological anthropologist, is heading a two-year research project aimed at investigating the evolution of language by looking at chimpanzees, our closest evolutionary cousins.
The Calls of Their Fathers
Wilson is the former Director of Field Research at Gombe National Park in Tanzania, made famous by Jane Goodall’s pioneering studies. And it is there that he and graduate student Nisarg Desai began their work this summer.
Why look at chimpanzees to unlock the riddles of human language? Chimpanzees are one of the two living species most closely related to humans, and studies of their behavior offer insights into our own evolution. Like humans, but unlike most other animals, chimpanzees make and use tools, hunt in groups, and engage in warlike attacks on their neighbors. Captive chimpanzees have been taught elements of symbolic communication, using American Sign Language and computer keyboards. But what about their natural communication?
What Wilson is looking to understand is this: are chimpanzees capable of vocal learning? The trait is a key one for understanding the evolution of language. Other studies have found evidence of vocal learning in primates–there have even been other studies of chimpanzee dialects–but vocal learning appears to be rare in primates.
“One of the things that’s really unusual about human language is that, compared to other mammals, we learn to modify our vocal production to an enormous extent,” he says. “We speak other languages. We can learn any language. That’s a big contrast to our primate relatives.”
Wilson’s team will focus on the pant-hoots of two different Gombe chimpanzee groups. A pant-hoot is a vocalization that allows the participants to identify each other through their individual vocal stylisations. “We’re pretty sure that chimpanzees have individually distinctive calls, that they can tell individuals apart from their pant-hoots. But can we detect differences between groups?”
Pant-hoots are the loudest and most conspicuous of chimpanzee calls and are therefore the easiest to record and study. These calls are also loud enough to be heard up to a mile away, and thus play an important role in male territorial defense. Because pant-hoots can be heard by hostile neighbors, it might benefit male chimpanzees to learn a pant-hoot that identifies not only who they are, but to what group they belong.
“Males have coalitions where they defend their territory against other males. Males stay in the territory that they’re born in their whole lives. So if they’re learning how to pant-hoot, they’re learning it from their male relatives and males in the community,” Wilson explains.
“So they might have an advantage by producing some signal that they belong to this community rather than the other community. This seems like it could be a plausible reason for the evolution of vocal learning, that they are learning the calls of their fathers.” But it’s also possible that fathers and sons have similar calls simply because of genetics. Because researchers at Gombe have genotyped nearly the entire population, it will be possible to tell whether acoustic similarity depends more on genetic similarity, or is simply a matter of group membership–which would be evidence of vocal learning.
The question of primate vocal learning is not a new one. Previous researchers have posed the questions but little headway has been made. Why?
“Because it’s hard science to do,” laughs Wilson. “It take a lot of hours on the ground, following chimps around with a microphone, trying to get recordings and then also, analyzing the acoustics properly is a big job.”
He and Desai explain some of the difficulties; Doing research in Tanzania is very expensive; not only are flights there expensive, but it also costs nearly $5,000 just to get the necessary research and residence permits. Getting a high quality, complete pant-hoot from a known individual is a difficult skill that takes time to learn. Plus, Wilson says, chimps can be very quiet animals, “If you watch them on TV or movies you can get the impression that they’re noisy animals, but in the wild they’re silent much of the time.”
Despite these difficulties, Gombe is an excellent place to conduct this research. The Gombe study is the first and longest continuing study of wild chimpanzees, begun by Jane Goodall in 1960. Wilson has been part of the Gombe research team since 2001.
The Tanzanian field assistants who collect the long-term data are experts in chimpanzee behavior, and can recognize individual chimps by their pant-hoots. This summer Desai trained field assistants on recording techniques; they will continue to gather data now that Desai and Wilson are back in the US.
Wilson and Desai now face the difficult task of extracting and analyzing the data. Computer software will be used to analyze the calls and statistics will be used to determine similarity of calls, frequency, and duration.
The project has been funded through the next two years by a Talle Faculty Research Award, and Wilson hopes to extend it if possible. “There is a great deal to do. This research at Gombe has been waiting for decades. It’s been a topic of debate in the research community…and it’s exciting to be able to finally get to work.”