The Trouble with Testosterone

by Robert M. Sapolsky

  Junk Food Monkeys

  David Gilhooly, Tall Excessive Sundae, 1991; courtesy John Natsoulas Press, Davis, California

  When’s the last time you thought about Jean-Jacques Rousseau? Remember his noble savage, his idealized view of mankind in its primordial splendor, when life was gentle, innocent, and natural? Not that most of us reject Rousseau’s thinking; it’s just that amid the bustle and ambition of the remnants of the Me Generation, it no longer seems fashionable to ponder the possibly superior moral state of primordial humans.

  As for their possibly superior physical state—now that’s an issue of more than passing concern, and here a Rousseauian view of sorts continues to hold sway. As a society that spends billions of dollars on medical care, health clubs, and looking good, what we want to know is: How was the physical health of primordial humans? What was their secret workout regimen for achieving their beautiful precivilized bodies? What were cholesterol levels like in the Garden of Eden?

  Many think that in certain respects early humans fared better than we do. When you subtract the accidents, infections, and infantile diseases that beset them, our forebears might not have had it so bad. In a 1985 article in the New England Journal of Medicine, physician-anthropologists S. Boyd Eaton and Melvin Konner did an ingenious job of reconstructing the likely diet of our Paleolithic ancestors, and they concluded that there was much to be said for the high-fiber, low-salt, low-fat diet.

  Anthropologists studying the hunter-gatherers in the Kalahari Desert, a group that’s believed to retain many of the ways of life of earlier humans, have come to similar conclusions. Among the !Kung tribe, for example, some maladies that we view as a normal part of human aging are proving not to be obligatory after all: hearing acuity is not lost; blood pressure and cholesterol levels do not rise; degenerative heart disease doesn’t seem to develop. As we sit here amid our ulcers and hypertension and hardening arteries, it is getting harder for us to avoid the uncomfortable suspicion that we have fallen from a state of metabolic grace.

  For the past decade I have been observing a group of some of our closest relatives as they fell from their own primordial metabolic grace into something resembling our nutritional decadence. My subjects are the olive baboons that I study during my summers in the Masai Mara National Reserve in the Serengeti Plain of Kenya. Chiefly I’m interested in the relationships between their social behavior and dominance rank, the amount of social stress the baboons experience, and how their bodies react to it. To study the questions I am interested in, I have to combine extensive behavioral observations with some basic lab work: drawing the animals’ blood, measuring hormones, monitoring blood pressure, and conducting other clinical tests to find out how their bodies are functioning. And in this context Rousseau reared his worrisome head.

  Masai Mara is a wonderful place to be a researcher. And it’s a fairly idyllic place to be a baboon, a vast untouched landscape of savannahs and woodlands and one of the last great refuges for wild animals left on earth. Herds of wildebeest roam on the open plains, lions lounge beneath the flat-topped acacia trees, giraffe and zebra drink side by side at the watering places. Inevitably Masai Mara has also become an attractive place to tourists, resulting in all the usual problems that occur when large influxes of people descend on previously virgin wilderness.

  One of the biggest problems here, as in our own national parks, is what to do with the garbage. The solution so far has been to dump much of it into large pits, five feet deep by thirty feet wide, hidden among trees in out-of-the-way areas. Brimming with food and refuse rotting in ninety-degree heat, infested with flies and circled by vultures and hyenas, the pits look like a scene from Hieronymus Bosch. And about a decade ago, one of the baboon troops that I study had such a Garden of Earthly Delights dumped right in the middle of its territory.

  For the baboons this was a major change in fortune, the primatological equivalent, perhaps, of winning the lottery. A major concern in any wild animal’s life is obtaining food, and an average baboon in the Serengeti spends 30 to 40 percent of each day foraging—climbing trees to reach fruits and leaves, digging laboriously in the ground to unearth tubers, walking five or ten miles to reach sources of food. Their diet is spartan: figs and olives, grass and sedge parts, corms, tubers, and seed-pods. It’s unusual for them to hunt or scavenge, and meat accounts for less than 1 percent of the food they consume. So the typical baboon diet teems with fiber and is very low in fat, sugar, and cholesterol.

  For the nouveau riche Garbage Dump troop, life changed dramatically. When I started observing them, in 1978, they had recently discovered the dump’s existence and were making an occasional food run. By 1980 the entire group—some eighty animals, ranging from twenty-five-year-old adults to newborn infants—had moved into new sleeping quarters in the trees surrounding the dump. Instead of stirring at dawn, these animals would typically stay in the trees, snoozing and grooming, and only rouse themselves in time to meet the 9 A.M. garbage tractor. The day’s feeding would be finished after half an hour of communal frenzy over the pickings. But it was the pickings themselves that made the biggest difference in the baboons’ lives.

  Once, in the name of science, I donned lab gloves, held my breath, and astonished the tractor driver by methodically sifting through his moldering garbage. The refuse was certainly a far cry from tubers and leaves: fried drumsticks or a slab of beef left over by a tourist with eyes bigger than his stomach; fruit salad gone a bit bad, perhaps left too long on the sundrenched buffet table; fragments of pies and cakes, and alarming yellow dollops of custard pudding, nibbled at by a disciplined dieter—processed sugars, fat, red meat, and cholesterol, our modern Four Horsemen of the Apocalypse.

  And what were the physiological consequences for these baboons in Utopia? First the good news: Young baboons grew faster, reaching developmental landmarks such as puberty at earlier ages. These beneficial changes were exactly what one would expect of humans switching from a lean subsistence diet to a more affluent Westernized fare. In the countries of the West the age of first menstruation has declined from an estimated fifteen years during the 1800s to our current average of about twelve and a half, and diet is thought to have much to do with that.

  The trend in baboons has been particularly well documented by Jeanne Altmann of the University of Chicago, a biologist studying both foraging and garbage-eating troops in another park in Kenya. Among her animals, eating garbage has led to the onset of puberty at age three and a half instead of age five. Females now typically give birth for the first time at age five, a year and a half earlier than before. Moreover, because the infants develop faster, they are weaned earlier; consequently, females start menstruating again that much sooner, and once they resume, they conceive more quickly. Indeed, Altmann’s garbage eaters have had something of a baby boom compared with their foraging cousins.

  Another advantage of garbage eating became clear during the tragic East African drought of 1984. During that period wild game found life extremely difficult. The luckier animals merely spent more time and covered more distance in search of food. The less lucky starved and succumbed to diseases previously held in check. However, tourists did not starve, and neither did baboons living off their detritus.

  So, at first glance, from the evolutionary standpoint of reproductive fitness, some daily custard pudding appears to do wonders, increasing reproductive rates and buffering the troop from famine. But now here’s the bad news: some of the same lousy changes seen in humans eating Westernized fare also occurred in baboons.

  Your average wild baboon eating a natural diet has cholesterol levels that would shame the most ectomorphic triathlete. University of Texas pathologist Glen Mott and I have studied a number of troops and found cholesterol levels averaging an amazing 66 milligrams in 100 cubic centimeters of blood among adult males. Not only that, but more than half the total cholesterol was in the form of high-density lipoproteins, the “good” type. In humans, cholesterol levels less than 150 with a third of the total in the
high-density form are grounds for bragging at the health club.

  But when we studied the Garbage Dump baboons, a different picture emerged. Cholesterol levels were nearly a third higher, and most of the increase was attributable to a rise in damaging low-density lipoproteins, the type that builds up plaque on artery walls. Joseph Kemnitz, a primatologist at the Wisconsin Regional Primate Research Center, analyzed blood samples from these animals and found that levels of insulin were more than twice as high in the Garbage Dumpers as in those eating a natural diet. This hormone is secreted by the pancreas in response to eating, especially eating rich, sugary food, and its function is to tell cells to store glucose for future use as energy.

  If insulin levels rise too high, however, cells become inured to its message; instead of being stored, glucose is left circulating in the bloodstream. It’s this state of affairs that can eventually lead to adult-onset diabetes, a distinctly Western malady. Since the Garbage Dumpers came from gene stocks similar to those of the natural foragers, genetic differences couldn’t account for their much higher insulin levels. The most likely suspect was their junk food diet and their relative inactivity.

  Are the Garbage Dumpers now at risk for diabetes and heart disease, candidates for celebrity diets and coronary bypasses? It is hard to tell; no one has ever reported adultonset diabetes in wild baboons, but, then, no one has ever looked. Surprisingly, people have looked at the cardiovascular systems of wild baboons and found fatty deposits in their blood vessels and hearts. Garbage Dumpers presumably run a higher risk of depositing fat in their arteries, but whether it will affect their health and life spans remains to be seen. One major impact on the health of Garbage Dumpers became clear in a grim way, however. If you are going to spend your time around human garbage, you’ll have to deal with whatever that garbage is infected with. And if these infectious agents are new to you, your immunological defenses are not likely to be very good.

  A few years ago some of my Garbage Dump animals became dramatically ill. They wasted away, coughing up blood, losing the use of their limbs. Three veterinarians from the Institute of Primate Research in Nairobi—Ross Tarara, Mbaruk Suleman, and James Else—joined me to investigate the outbreak and traced it to bovine tuberculosis, probably from eating contaminated meat. It was the first time the disease had been reported in wild primates, and by the time it abated it had killed half the Garbage Dump troop. For them, there had been no free lunch after all.

  Has the Westernization of these animals’ diets thus been good or bad? This is much the same as questioning the benefits of our own Westernization. Toxic wastes and automatic weapons strike me as bad developments; on the other hand, vaccines, thermal underwear, and eighty-year life expectancies seem like marvelous improvements upon the Middle Ages. All things considered, we seem to have benefited, at least from a health perspective.

  For the baboons, too, the answer must be carefully considered. Growing fat is unwise if you plan to sit in an arboreal armchair, but very wise if you’re about to face a dry season. Similarly, a nice piece of meat is a fine thing during a famine, but not such a hot idea if it’s contaminated.

  It is platitudinous to say that this is a complicated issue, but it is clear that life for the foraging baboon is not one of pure Rousseauian ease, nor life for the garbage eaters one of unambiguous decline. My bias is that the latter’s health has, on the whole, suffered from their garbage trove. But what has struck me in these studies is that there are also benefits and the judgment is somewhat difficult to make. It seems that even for a baboon, just as for us, there are few unambiguous rules for figuring out what to do with the choices life throws in our laps.

  FURTHER READING

  The salutary diet of our ancestors is discussed in S. Eaton and M. Konner, “Paleolithic Nutrition: A Consideration of Its Nature and Current Implications,” New England Journal of Medicine 312 (1985): 283. The reader might also want to check a more accessible version of the same, namely: S. Eaton, M. Shostak, and M. Konner, The Paleolithic Prescription: A Program of Diet and Exercise and a Design for Living (New York: Harper and Row, 1988).

  Cholesterol levels in wild baboons is considered in R. Sapolsky and G. Mott, “Social Subordinance in Wild Baboons Is Associated with Suppressed High-Density Lipoprotein-Cholesterol Concentrations: The Possible Role of Chronic Social Stress,” Endocrinology 121 (1987): 1605.

  The effects of diet on metabolic profiles in wild baboons is covered in J. Altmann, D. Schoeller, S. Altmann, P. Muruthi, and R. Sapolsky, “Variability in Body Size and Fatness in a Free-Living Nonhuman Primate Population,” American Journal of Primatology 30 (1993): 149.

  The vulnerability of primates living on garbage diets to infectious diseases is covered in depressing detail in two papers: R. Tarara, M. Suleman, R. Sapolsky, M. Wabomba, and J. Else, “Tuberculosis in Wild Baboons (Papio cynocephalus) in Kenya,” Journal of Wildlife Disease 21 (1985): 137; and in R. Sapolsky and J. Else, “Bovine Tuberculosis in a Wild Baboon Population: Epidemiological Aspects,” Journal of Medical Primatology 16 (1987): 229.

  The Burden of Being Burden-Free

  Clifford Goodenough, Figure Walking in a Landscape, 1991; courtesy Davidson Galleries, Seattle

  After grad school, I spent a few years doing research at the Salk Institute in San Diego, a famously magnificent structure perched on the edge of a cliff overlooking the Pacific. Next door was a hang gliding center, and its denizens would often glide past the windows of my upper-floor lab. For some reason, I had decided that the sport was idiotic, its practitioners a bunch of irritating cowboys. One morning, I glanced up from, perhaps, my thousandth pipetting of the day, and my eyes briefly locked with those of a passing hang glider. It occurred to me in that instant that we were having the identical thought: “No way in hell would I like to be in your shoes, buddy.”

  One person’s pleasure, another’s poison. This fool had paid good money to glide around the cliffs, while I’d do the same to get to spend sixteen hours a day toiling away at my science. And for each of us, the other’s activity would probably count as a stressful misery.

  It is quite clear that you have a major medical problem on your hands if you are gored by an elephant or if you contract dengue fever. But it is far from clear if, instead, you are subjected to years of traffic jams, mortgages, deadlines, or relationship problems—maybe they represent profound psychological burdens, or maybe they are things you barely notice. We differ tremendously as to what psychologically stresses us. Obviously, we also differ tremendously as to the diseases we get and the courses they take. And there are reasons to think that how much we are buffeted with stressors may have something to do with what sorts of diseases afflict us.

  A lot of research in health psychology has explored the immensely important fact that certain personality types seem to be predisposed toward stress-related disease, or toward secreting too much of certain hormones that can cause stress-related disease. The most frequently studied of these hormones are adrenaline and glucocorticoids. These hormones are secreted directly into the bloodstream and help you adapt to an acute stressful crisis by mobilizing the fight-or-flight response. However, if these same hormones are secreted chronically because of psychological stress, as seen in certain personality types, they can cause a variety of maladies. And some individuals with these personality types already show the stigmata of those maladies—elevated blood pressure, irritable bowels, reproductive suppression, irregular sleep. Why are their bodies working differently from most people’s?

  Most broadly, a stressor can be defined as a physical or psychological challenge that upsets the body’s equilibrium,6 and coping responses are what help reestablish such equilibrium. Obviously, one would like there to be an appropriate match between the type of stressor and the type of response. For example, it is generally a wise thing to come up with a response such as “I know what I did wrong, and I can avoid this happening again” when confronted with a bad test score, and to come up with a massive diversion of energy to your thigh muscl
es when confronted with a predatory lion—and not the other way around. In addition, one wants a fairly good match between the intensity or duration of stressors and responses—a mild threat should not involve vigilant hypertension for hours afterward. Framed these ways, a common theme among many of these personality types that are predisposed toward stress-related diseases is a discrepancy between the stressor a person is pummeled with and the style of coping response mobilized.

  One example of such maladaptiveness would be people with a major depression. A classic picture of many depressives is that, as a result of life’s painful lessons, they have learned to be helpless. When faced with stressful challenges, they give up before things have even started. They don’t attempt to cope or, if they happen to stumble onto something effective, don’t recognize it for what it is. And, as has been known for decades, such depressives often have elevated stress hormone levels in their bloodstream.

  A similar physiologic profile is seen in people who are at the opposite end of the spectrum when it comes to coping with things the wrong way. People with anxiety disorders can be thought of as persistently mobilizing coping responses that are disproportionately large. For them, life is filled with threats around every corner, threats that demand a constant hyper-vigilance, an endless skittering search for safety, a sense that the rules are constantly changing. A similar picture occurs in “Type A” individuals, but with a twist. Type A represents perhaps the most durable and studied of personality types that carry a disease risk. As initially characterized in the 1960s by the cardiologists Meyer Friedman and Ray Rosenman, Type A individuals are immensely competitive, overachieving, time-pressured, impatient, and hostile. A zillion studies later, it has become clear that the key component of Type A personality is the hostility—they perceive a need for coping responses that are disproportionately large, and their coping responses are disproportionately likely to be angry ones. Give a Type A individual an unsolvable puzzle, make them role-play an interpersonal conflict, expose them without their knowledge to a research confederate who (unbeknownst to them) deliberately botches a job . . . and the Type A individual boils. They view every frustration as an intentional, personal, malevolent affront . . . and their bloodstream fills with stress hormones and their blood pressure soars. For them, a lifetime of such corrosive discrepancy between stressor and response can eventually exact a major cardiovascular price.