Like humans, most of baboons' stress comes from social interactions.

It's not easy being an antelope. You could be grazing peacefully one minute, fleeing a hungry predator-literally running for your life-the next. That's why mammals have evolved a physiological response to stress that enables them to devote all their efforts to running away from danger. Called the "fight or flight" response, hormones released by a stressful situation increase blood pressure, blood flow and heart rate while quickly mobilizing extra energy. At the same time many of the body's other systems are shut down.

Sound familiar? Maybe you experienced a similar feeling the last time you had to speak in public, go to the dentist or take a challenging test. That's because social situations can trigger the fight or flight response in primates-the biological family that includes humans, apes and monkeys.

In "The Primates' Stress Club," Alan meets Stanford University researcher Robert Sapolsky, who has studied the complex rules of baboon social life for thirty years. For baboons-smart, successful primates with no real enemies- competing for social position turns out to be a major source of stress.

Sapolsky uses blood samples to measure tress hormones.

In Kenya's Masai Mara reserve, Sapolsky watches as two males engage in a silent, psychological battle. Only someone with a trained eye would even know the baboons had duked it out. Sapolsky has spent decades observing baboon behavior and taking blood samples to look for stress hormones. As a result of such "psychological nonsense" as he calls it, baboons -- and people -- experience extreme fight or flight stress responses.

But while antelope physiology returns to normal as soon as the danger has passed, primates can remained stressed out over the long term.

"Those stress hormones can be a very good thing for that 10-second sprint," says Sapolsky, "But do it chronically and they can be very damaging." .

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