Consider the plight of a certain high-ranking hominid who moves into a new habitat, a place we’ll call Netherfield Park. After some social contact with the eldest of the neighboring female offspring, he has a strong urge to mate. But his own sisters interfere because of her “low connections” and “vulgar relations.”

The male hominid goes by the name of Mr. Bingley; the female, Miss Jane Bennet. Both inhabit the special preserve of one Jane Austen. As Pride and Prejudice illustrates, Homo sapiens carry a keen sense of who’s related to whom, and how others stack up in the social rankings. It turns out we aren’t the only ones.

According to two Penn primatologists, Dr. Robert Seyfarth and Dr. Dorothy Cheney, baboons appear to do the same—a finding that may shed light on theories about the evolution of human cognition and language.

Cheney, professor of biology, and Seyfarth, professor of psychology, have spent more than 25 years studying the communication, cognition, and social behavior of non-human primates, including vervet monkeys in Kenya and baboons in Botswana. Their work, including the 1990 book How Monkeys See the World, has illuminated similarities and differences between humans and some of their closest relatives.

“The basic premise that we start off with,” says Seyfarth, “is that you can’t understand an animal’s brain and how it works without understanding the society in which that brain lives.”

That brings Cheney and him to the Moremi Game Reserve in the Okavango Delta. The three-square-mile swath of woodland and savannah is home to a formidable mix of lions, leopards, hyenas, and elephants, along with a troop of about 80 baboons. With the aid of binoculars, hand-held computers, recording devices, and vials of poop preservative (for hormone testing), Cheney, Seyfarth, and their assistants methodically track the movements of the Papio hamadryas ursinus. Following the baboons at a distance of about six feet, they avoid eye contact and interact with their subjects as little as possible.

Baboons are the long-snouted bullies of the savannah, with the bigger male growing to about the size of a Labrador retriever. They aren’t afraid of much, Seyfarth says. “And what they are afraid of—with the exception of lions—their attitude is, ‘Let’s fight it.’”

They dine on fruit from the local mangosteen trees, wild figs, rodents, and vervets. Access to prime feeding spots goes to the highest-ranking individuals—and every baboon appears to know who they are.

“If you look at a group of baboons, you’ll see females arranged in a dominance hierarchy,” says Cheney during an interview with both researchers in her Leidy Laboratories office. They maintain close bonds with their kin. The females assume ranks just under their mother in inverse relation to their birth order, and an entire family tends to be above or below the next. “You’ve really got a kind of hierarchy of families—like in a Jane Austen novel.”

It’s 9:30 a.m. on the game reserve. A member of Family A chases and bites a member of Family B. Fifteen minutes later, a member of Family B looks over and threatens a member of Family A.

The question Cheney and Seyfarth have tried to answer is how much the animals themselves understand the complex system in which they’re participating: “It looks like these monkeys are very, very good at this,” Cheney says. The baboons’ videotaped reactions to simulated fights show that they recognize not only their own place in the social network, but the ranks and relationships of others in their group. Furthermore, they recognize that not all social interactions carry the same weight.

Feuds between families—think of the Montagues and Capulets—are a bigger deal than feuds within families. A rank reversal between two sisters will only affect rank relationships within the family, but if two members of different families reverse rank, it will cause two entire matrilines (female kin groups) to follow suit.

In the November 14 edition of Science, Cheney and Seyfarth—with post-doctoral researchers Thore Bergman and Jacinta Beehner—published results of a study in which they recorded vocalizations of 19 adult female baboons and played them back in different sequences over a hidden loudspeaker.

When individual baboons heard a vocal exchange between two others that was consistent within the existing hierarchy (such as the more dominant animal B threatening C), they looked toward the sound briefly—about 1.4 seconds on average—and then went about their business. The average looking time increased to 2 seconds, however, when exchanges that appeared to go against rank within a family took place (C threatening B). It increased to 4.2 seconds in reaction to a “rank reversal” between baboons of two different families.

Upheavals among female baboons are rare, and higher-ranking families generally support the status quo, Seyfarth says. “It’s very Jane Austen.”

“If the whole hierarchy is upset, it could upset you, too,” Cheney points out.

Female rank has nothing to do with size or age and everything to do with who your allies are. Though rank order among baboon matrilines can remain stable for several generations or more, families can lose dominance when they lose members. (Male baboons, which leave home as adults and are dominant to all the females, play by a different set of rules, in which chutzpah, fighting ability, and big teeth come in handy.)

Baboons split from the common ancestors of humans and apes about 35 to 40 million years ago, so they are not nearly as closely related to people as chimpanzees are. (But apes are harder to study in their natural habitats, which are in politically less stable countries.) Like other monkeys baboons don’t use tools and they don’t show the kind of cultural behavior seen in chimpanzees. And yet they appear to have a sophisticated social knowledge.

To give one example, a low-ranking female baboon interested in upward mobility might go about it by becoming “very close buddies” with a higher-ranking baboon—perhaps by picking ectoparasites from her coat or forming an alliance with her during a fight.

There is some anecdotal evidence that “if you’re a very low-ranking female, you do better if you don’t have any relatives,” Cheney says. “You can freelance. You can establish a very close bond, particularly if you’re young, with a middle- or high-ranking family.”

When one observes such tactics, says Seyfarth, “That leads you to say, maybe these are the kinds of social pressures that cause primates to have big brains. They’ve got to know a lot of stuff in order to pursue the best social strategy.”

And the pressures to sort matters of rank and kinship in a complex society may have favored the evolution of humans’ ability to sort words and make meaning out of sentences.

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2004 The Pennsylvania Gazette
Last modified 04/27/04

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

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