Stanford University biologist Robert Sapolsky travels thousands of miles each summer to try to better understand stress.
He has spent more than 15 summers in the forests in the East African Serengeti, where he carefully monitors a troop of olive baboons he hopes will help unlock the secret of stress.
With the crudest of tools, he painstakingly watches and records the baboons' daily lives, identifying leaders and followers and collecting blood samples to be tested for hormonal changes. His lab equipment runs off a Jeep battery. His refrigerator is a Styrofoam box buried in the earth.
"Baboons have the exact physiology as humans do," Sapolsky said. "They also get the same stress-related illnesses, such as ulcers and heart disease." What also made the baboons a good example of human stress is that they were living in a natural habitat in the Masai Mara National Reserve in Kenya. The animals do not have to fight each other for food.
"Sapolsky is a daring scientist," said Dee Higley, a senior staff fellow at the National Institute on Alcohol Abuse and Alcoholism, describing some of the perils of working with baboons. "He goes out with little more than a blowgun and puts his life on the line every time he collects data."
For years, Sapolsky's studies on life in the jungle found that the baboon leaders had the least stressful job--and the lowest levels of cortisol, a common stress hormone. This finding would suggest that bosses create stress for others rather than feeling it themselves.
But his theory about social dominance as measured by key stress hormones changed dramatically when he began to see that some of the leaders had very high levels of stress hormones and some non-dominant baboons had surprisingly low levels.
What Sapolsky hadn't accounted for was that the baboons' personalities were strong enough to sway stress hormones, which may be the key to where a baboon fits into his environment.
"I used to think that social rank has everything to do with how the body works," Sapolsky said. "But it turns out it's more subtle than that. Personality is one of the most important predictors. It's not a baboon's place in the group, but his coping style."
The animals with the lowest levels of stress hormones were those who could control threatening events and distinguish between some real danger and an imagined one. The least stressed baboons were those that turned to friends for comfort after dealing with threatening situations.
"Baboons are just like humans," Sapolsky said. "They can see the glass half full or half empty."
The biologist and his wife, Lisa Share, and Kenyan researcher Richard Kones log the countless behaviors of the troop members from dawn to bedtime. On days they are not recording behaviors, they are using a blowgun to anesthetize baboons to collect blood samples and run tests. At first, Sapolsky observed that the lower an animal was in the troop's ranking, the higher the level of cortisol, one of the main stress hormones; the higher the blood pressure, and the fewer the white blood cells available to ward off infections.
When he looked further, it turned out that the dominant baboons who did best were the ones with certain stress-protective personality traits. For example, those with the lowest levels of stress hormones were able to tell the difference between a tense social situation and a neutral one.
Those with double the stress hormones were unable to tell the difference between a rival about to start a fight and one about to take a nap a few hundred yards away.
Baboons who had strong social ties seemed to have the best stress-response profile, Sapolsky found. These males were friends with female baboons (grooming them and letting themselves be groomed), and they played with children. He suspects that these personality traits are stable.
Sapolsky's work has shown that these same stress hormones, glucocorticosteroids, can endanger cells in the area of the brain that govern memory and learning.
These stress hormones can kill neurons also, he said. The findings have been confirmed in rats, monkeys and one human patient with a lesion in the hippocampus.
Sapolsky wonders whether high doses of steroids, similar to the stress hormones pumped out by the body, could be damaging brain cells.
Studies also have been done in violent humans, repeat sex offenders, arsonists and serial murderers, all of whom have extremely low levels of the serotonin metabolite. Higley has used Sapolsky's findings to better understand his own work with stress hormones.
The federal researchers are intent on understanding the physiological response behind certain social skills, such as getting along well with others. They study a group of animals living on Morgan Island, off the coast of South Carolina. They've selected 75 of the 4,500 males to study and have been following them from birth into puberty.
Because they have immediate access to electricity and laboratories, Higley and his team do more complex blood and cerebrospinal fluid work. In one study, for example, they are measuring a metabolite of serotonin, a brain chemical linked to aggression and violent behavior. Studies have shown that animals and people with low levels of the metabolite 5-HIAA tend to be more aggressive.
Army researchers saved an animal that killed two monkeys in the lab so that Higley could study the violent streak. In the cerebrospinal fluid, he said he found the lowest levels of 5-HIAA he had ever seen.
"It was amazing. The correlation was there, and very strong," said Higley.
They are now breeding the next generation of what he calls "juvenile delinquents." The violent rhesus monkey with the low 5-HIAA levels has been prolific, producing 11 infants so far. He has mated with animals with high and low levels of the metabolite. The offspring will be followed to see which tend toward violence.