Robert W. Sussman, Ph.D., professor of anthropology in Arts & Sciences, and a colleague found that affiliative behavior -- or friendly behavior like grooming and playing -- is probably a hundred times more frequent than aggressive behavior in primates, and that aggressive behavior constitutes less than 1 percent of primates' activities.

Robert W. Sussman

Sussman and Paul A. Garber, Ph.D., a former graduate student of Sussman's who is now chair and professor of anthropology at the University of Illinois at Urbana-Champaign, did a survey of the literature and followed that up with real-life observations. They had two questions: How much time do primates in general spend in social behavior, and how much of this social behavior is spent in aggressive interaction?

"The basic premise right now about animals that live in groups -- including humans -- is that they are constantly competing for resources," said Sussman, who is immediate past editor of The American Anthropologist. "It's a simplistic view of Darwinian survival of the fittest, but many scientists have taken it on. They state that almost all behavior is related to how animals strategize to compete with one another so that they can gain more resources and reproduce more. We think this is a very narrow and unsophisticated view of evolutionary theory."

In fact, Sussman says he and his colleagues are bucking a trend.

"We found in almost all species across the board, from diurnal lemurs -- the most primitive primates -- to apes, that less than 10 percent of their day and usually less than 5 percent of their day is spent in any active social behavior whatsoever," Sussman said. Social behavior, unlike everyday maintenance behavior like feeding and traveling, can be any kind of interaction such as touching, fighting or grooming, Sussman explained.

"Then we looked at the aggressive behavior of primates and found that usually less than 1 percent of their day is spent fighting or competing, and it's usually much less than 1 percent.

"Basically, what animals do is they interact in a general, coordinated way. There is not a lot of social behavior but most of the social behavior is affiliative, and we find that aggressive behavior is extremely rare, even in baboons, thought to be among the most aggressive primates."

Sussman and Garber presented their results Feb. 15 during the symposium "Rethinking the Role of Affiliation and Aggression in Primate Groups" at the annual meeting of the American Association for the Advancement of Science (AAAS).

This symposium was part of a series of research conferences exploring the biological roots of human nature from a multidisciplinary perspective. Sussman is a consultant to the AAAS Program of Dialogue on Science, Ethics and Religion, which has been conducting these conferences and symposia over the past three years.

Sussman's research includes a long-term study of the demography, ecology and social organization of the ring-tailed lemur at the Beza Mahafaly Reserve, which he co-founded, in southwest Madagascar.

In addition to studying the literature, Sussman wanted to observe primates' interactions firsthand. Last summer in Madagascar, Sussman, a Malagasy student and two Japanese researchers each studied one lemur from sunup to sundown.

"We had four different people looking at four different animals all day to see how many social interactions and fights the animals got into throughout the day," Sussman said. "Again it fit exactly what we had found in the literature: Less than 5 percent of the behavior of the animals was social and there was almost no aggression.

"The two Japanese researchers had been at the site studying these animals for 14 months," Sussman added. "They were amazed after observing just one throughout a day. They said they couldn't believe it, when they looked at one animal, how little it interacted. They hadn't put it in that context before."

Sussman said the daylong observation demonstrates the importance of putting the interactions into context. Of the aggressive interactions among the four animals being observed, all were considered to be events, which are instantaneous happenings, as opposed to bouts, which are measured in time.

And the most frequent agonistic interaction was when two animals got to the same place at the same time.

"They only had one of two alternatives," Sussman said. "They could either greet one another or have a short spat just because they had to do something. It was almost by happenstance: 'Well, what do I do now?' So rather than greeting, which would be putting their noses together or something like that, they might have a short spat and that was basically all of the aggressive interaction.

"Essentially what I am saying is people haven't studied the context of aggression and social behavior and affiliation to see how they all relate and actually organize the animal's life. That is something we want to do," Sussman said.