For more than 20 years Robert Sapolsky has left his busy laboratory at Stanford University behind each summer to experience the taxing world of baboons in the Serengeti. Like many of us, these primates dont spend most of the day worrying about their next meal, and so like many of us, they are prey to mental stress. "Baboon societies are ironically a lot like Westernized humans," Sapolsky says. "Were ecologically privileged enough that we can invent social and psychological stress. Baboons in the Serengeti, who only work three hours a day to meet their caloric needs, are similarly privileged. They ulcerate because of social complexities."

Over the years, Sapolsky has carefully documented how the baboons interact and matched that information with measures of their healthfor instance, levels of stress hormones, antibodies and cholesterol. The good news is that we can learn from what Sapolsky sees the monkeys do. Describing some of his work at the annual meeting of the American Association of the Advancement of Science on Sunday, he identified several behaviors that helped baboons mitigate the physical costs associated with mental stress.

First, he has found that males with the lowest levels of stress hormones also spend the most time grooming and being groomed by females who are not in heat (and so not of immediate sexual interest) and playing with infants. Second, monkeys who cannot gauge the seriousness of a threat have stress hormone levels that are twice as high as those who can distinguish real danger from histrionics. Similarly, baboons that wait for a fight are more stressed than animals that take control of a situation and strike first. In other words, make friends and keep things in perspective.