The grunts, wahoos, and barks of baboons are part of the background music of the game reserve. Sometimes they signal a squabble: a threat-grunt rumbles forth from one baboon, followed by a submissive scream from another that sounds to the untrained ear like a parrot being squashed. Depending on how you divide it up, baboon communication consists of six or 40 distinct calls.

This puts baboons in a similar category with mollusks, which communicate with 15 to 35 “qualitatively distinct, significant displays,” according to Dr. Mark Liberman, professor of linguistics and director of Penn’s Institute for Research in Cognitive Science.

“It doesn’t mean monkeys aren’t a whole lot more complicated or smarter than squid, but in this dimension, there doesn’t seem to have been a lot of [evolutionary] change,” he says. “One of several puzzles about language is what happened a while ago, whenever it was—two and a half million years or 200,000—to push us off in this direction that leads us to having 60,000 different signs or more.”

One challenge in understanding the higher cognitive abilities of humans, especially language, Liberman adds, is that “we don’t have very clear animal models for them” like we do with visual perception or hand-eye coordination. “So whatever comparisons we can come up with through the work of people like Seyfarth and Cheney are all the more precious, I think.”

Both collaborators and spouses, Seyfarth and Cheney met in college. Later they became graduate students in zoology at Cambridge, working with Robert Hinde, a leading figure in animal behavior and supervisor to Jane Goodall. They came to Penn in 1986 after working at Rockefeller University and UCLA.

Liberman calls their work on “how animals communicate with each other and we might communicate with them … the most clear-headed and careful and systematic and well controlled and insightful that is around,” adding that, “They’ve also taught and influenced many of the people doing good work in that field.”

One problem in solving the language puzzle, notes Seyfarth, is that there are no primitive languages—in other words, languages that can be seen as simpler than another. “If you wanted to explain the evolution of bipedalism, paleontologists could take you to some bones and say this is why this creature was on its way to becoming bipedal, but it was not there yet,” he says. “It’s much harder to look to a system of communication in animals or language in humans and say this is on its way to becoming language, but it isn’t there yet.”

Some insights have come from studies of children’s language-learning, which show that “such learning does not emerge completely on its own but instead begins with the child’s understanding of objects and events in the world,” Seyfarth and Cheney write in an email. “Before the child has words, she has a kind of conceptual structure.” Dr. Lila Gleitman, Dr. Henry Gleitman, and Dr. Elizabeth Shipley, all psychologists at Penn, showed many years ago that “children comprehend complex sentences long before they can produce them, and that children are aware of grammatical errors long before such knowledge appears in their own speech.” (Even dogs—which don’t produce linguistic communication—seem to understand it in some way when it is used by humans, Seyfarth and Cheney point out. And, as their own work shows, baboons have a small vocal repertoire compared to humans, but, “They seem to understand a great deal about their environment.”)

“As with the development of language in children, people generally believe that language evolved from a rich cognitive structure in our pre-linguistic ancestors,” Cheney and Seyfarth write. Their own work proposes that the roots of language lie in “our structured hierarchical knowledge of social relationships.”

According to Liberman, a number of theories focus on social relations, including the ideas that language emerged out of the need to “make what were in effect marriage vows”—public promises “basically [about] male food provisioning in return for female sexual fidelity”—or to “provide pleasant social bonding via gossip.”

“It’s very clear that primates are extremely social animals [with] complicated social networks and social hierarchies based on genetic relationships and alliances—who was nice to whom, who was mean to whom in the past,” Liberman says. “So it’s very important to primates to keep track of those structures and reason about them—and perhaps to communicate about them.”

Cheney and Seyfarth’s work is “interesting not only in that it suggests that social organizations might have been one of the kinds of structures that linguistic forms nucleated around, but it also connects these other ideas with what it was that motivated our ancestors to develop language in the first place.”

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2004 The Pennsylvania Gazette
Last modified 04/27/04

Who's Who on the Savannah
By Susan Frith
Illustration by Noah Woods

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