While apes and humans are normally peaceful in their home environments, they both possess a tendency to kill when abroad, said Harvard University Professor of Biological Anthropology Richard Wrangham.
Wrangham, invited to speak by Brown's Haffenreffer Museum of Anthropology, explained his theories before a near-capacity audience of 150 in Salomon 001 Thursday afternoon.
Wrangham said there were two views of human nature, developed by Enlightenment writers Jean-Jacques Rousseau and Thomas Hobbes. In the Rousseauian view, humans are a naturally peaceful species. Killing is unnatural, evil and done for rewards. However, in the Hobbesian view, all humans are naturally aggressive and will kill whenever the opportunity presents itself. Wrangham believes that humans are defined by a combination of the two views.
"Humans are Rousseau at home and Hobbes abroad," he said.
Wrangham, who is also the director of Kibale Research Project in Uganda, came to his conclusions after analyzing results from chimpanzee observation projects from the past four decades. As one of the closest species to humans, he said, chimps were ideal for a comparative study.
Within their own communities, chimps and humans showed relatively peaceful tendencies, Wrangham said. Though male chimps often beat females, it almost never resulted in death. Human communities fought at a significantly lower rate than chimps, he said.
However, the killing rate between different communities, both of apes and humans, is much higher, Wrangham said. The main reason chimps kill is rival removal, he said. Chimp communities seek to eliminate rival communities to expand their territory, which in turn leads to a faster reproductive rate.
Wrangham said there is evidence that there were high killing rates between human societies as well.
"War has been a regular feature of hunter-gatherers," he said. "There have been very high killing rates among all known simple hunter-gather societies."
Wrangham also spoke about how chimps and humans tend to kill only when it is safe. For example, chimps are very selective in their killings. Chimps usually try to pick off solitary apes from rival communities. Normally, a killing occurs when a large group of male chimps, ranging from four to 15, encounters a single male chimp from another community.
Humans also try to fight only when it is safe, Wrangham said. Hunter-gather societies usually attack only when they have the element of surprise. In state wars, most killings occur only when one side has an advantage. It is rare for two armies to line up against each other and charge, such as in "Braveheart," he said.
Also, in most battles, soldiers are usually not killed in one-on-one combat. Wrangham said most killings on a battlefield occur when one soldier finds himself against several soldiers. He added that most victims in large battles are helpless, citing as an example that soldiers die in the largest numbers when they run.
In battle, humans try to avoid killing because it is often traumatic. But soldiers kill out of fear, he said. They are afraid of letting down their fellow soldiers, of punishment from their superiors and of their own death from the opposing army.
Large-scale state wars occur due to the overconfidence in a state's ability to win, he said.
"As you approach conflict, leaders overestimate their power to win, underestimate those of the opposition and ignore intelligence reports," Wrangham said. If both sides believe they are going to win, they will commit to the conflict, he added.
Reaction to Wrangham's lecture was positive.
"I think it was an excellent presentation," said Professor of Anthropology Richard Gould, who introduced Wrangham. "He's asking the right kind of questions. ... One has to look at both the biological and cultural components of anthropology."
Isaac Haxton '07 also said he enjoyed the presentation. "I thought it was interesting that he suggested people suffer psychological damage when there's a risk (involved in killing), but they don't when it's safe," Haxton said. "It's upsetting."
But one student found hope in Wrangham's lecture.
"I was struck by how other primates like the bonobo were non-violent," said Caitlin Clay '08. "The fact that there exists a non-violent primate gives me hope."
