The Graying of the Troops

Baboons who live to a ripe old age are the ones who know what friends are for.

By Robert Sapolsky|Friday, March 01, 1996
RELATED TAGS: PRIMATES, AGING
This was one of those days when all his joints ached. The rains had started and the humidity inflamed his hips and knees, especially the one he had injured long ago in his youth. He hobbled across the field to look for something to eat and then, perhaps, to sit with a friend. Finding palatable food was becoming increasingly difficult as he lost more teeth-- sometimes it seemed he spent half the day just trying to make the hunger go away. He paused for a moment, a bit disoriented, briefly unsure of his direction. When he was young, he had sprinted and chased and wrestled with his friends in this field.

As he resumed his path, two strangers emerged from behind a tree. He tensed. The two were not quiet the way newcomers usually were. They were confident, and clearly troublemakers. They worked together. Maybe they were brothers; he didn’t know.

He was frightened and found himself breathing faster. He scratched nervously at a sudden itch on his shoulder, then glanced down, making no eye contact, as they approached. He felt a swelling of relief as they passed him, but it was short-lived. They spun around. The nearest one shoved him hard. He tried to brace himself with his bad leg, but it was too weak and buckled under him. He shrieked in fear. They leapt on him, he saw a flash of something sharp, and, in a spasm of pain, he felt himself cut-- slashed across his cheek and on his back. It was over in a second. As they ran off, leaving him on the ground, the second one yanked painfully on his tail.

Social scientists have often noted that our society, like other Western ones, is graying, and that it is novel for a human population to have a substantial percentage of elderly individuals. Just imagine, though, how much rarer the phenomenon is among animals wrestling with nature’s bloody tooth and claw. Decrepit gazelles or wildebeests or warthogs are not typical features of the savanna.

The rarity of truly aged organisms in the wild has nothing to do with how long they live. A fruit fly can be old within a few days, while a redwood might live for a millennium without feeling its age. Aging can be defined, on an individual level, as an increasing vulnerability over time to exogenous insults: the same environmental kick in the rear is more likely to do you in as you get older. As an obvious example, 20-year-old human pelvises remain in one piece after a fall on the ice more often than 80-year-old pelvises do.

Relatively few species on Earth get old and vulnerable as we do, though no one really knows why--or why those few include most of the complex vertebrate species. Even among those that do age, relatively few individuals live anywhere near the theoretical maximum for their species. Teeth are lost that would help forage, immune systems are weakened past the point of protecting against an injury, legs become a bit too feeble to outrun a predator. Survival is a young vertebrate’s game.

Yet old individuals occasionally survive and even thrive. In general, they are found among the more social, complex, ecologically successful, and adaptive species. Elephants live in large social groups, their lives filled with social complexity, support, and care; a truly ancient animal may remain alive by dint of her cumulative knowledge and the help of her family and friends. The same might be seen among certain social predators, such as lions. And one is perhaps most likely to see a truly old animal out in the wild among social primates.

For nearly 20 years, I have spent my summers studying the behavior and physiology of a population of wild baboons in the Serengeti of East Africa. These are smart animals with pungent, individualistic personalities, living out 20- to 25-year life spans in large social groups. With them, I’ve been able to experience the shock of mortality in a truncated way--watching baboons who used to be terrors of the savanna become hobbled with arthritis, or shuddering at the weathered state of a male who was a subadult primate like me in the l970s, when I began my work. They’ve gotten old on me.

With the graying of some of my troop, I’ve gotten the chance to understand how the quality of their later years reflects how they lived their lives. In particular I’ve been able to observe an odd practice among elderly males that, though it seemed inexplicable at first, was ultimately illuminating. It contains a lesson, I think, about how the patterns of a lifetime can come home to roost.

In most old-world primate societies, such as those of baboons, females spend their entire lives in the troop into which they were born, surrounded by their female relatives. Males, on the other hand, tend to leave the troop around puberty, shipping off to parts unknown to make their fortune. The pattern is common to most social species, since when one of the sexes emigrates, the group avoids inbreeding. In many species the members of one sex are driven out at puberty: among impalas, for example, the resident breeding male forces other males out as soon as he sees their horns--the first sign that they are becoming sexual competitors. Primates, though, leave voluntarily. They are possessed of a profoundly primate wanderlust, an itch to be anywhere but the drab, familiar home ground. They leave and gradually make their way into a new troop where they’re subordinate and unconnected at first, then slowly form connections as they grow into adulthood. It is a time of life fraught with danger, potential, fear, and excitement.

Sometimes a prime-age male baboon will also change troops. Invariably, this is purely a career move for him--a coalition of males has just unseated him from his position; some imposing competitor has seized the top spot in the hierarchy; and it’s an expedient time to try rising on another troop’s corporate ladder.

Every once in a while, however, an elderly male primate will transfer troops, and this, on the face of it, makes little sense. Old age is no time of life for an animal to spend alone and unprotected in the savanna, having left one troop but not yet assimilated into another. Senses are less acute, muscles are less willing, and predators lurk everywhere. The mortality risk for a young baboon increases as much as tenfold during the vulnerable transfer period; just imagine what it must be like for an elderly animal.

Even if the old baboon makes the transition to his new troop safely, he’ll hardly be on easy street. As he moves into a world of strangers, he will have to learn new social and ecological rules: which big, strapping males are unpredictably violent, which grove of trees is most likely to be fruiting when the dry season is at its worst. The new demands will be even harder for him because of the nature of cognitive aging. Crystallized knowledge, the recalling of facts and their application in usual, habitual ways, may remain intact into old age, but fluid knowledge, the absorbing of new information and its novel and improvisatory application, typically slips. It is an inauspicious time of life to learn new tricks.

The physical vulnerability, the need for continuity, the reliance on the familiar--all suggest that it is madness for a baboon to pick up in his old age and try a new life. Why should he ever do so? A number of scientists have come up with some ideas. Perhaps the grass is greener in some other troop’s field, making for easier foraging. Perhaps the animal believes that a move will give him the chance for a brief last hurrah in some other troop. One theory has the poignant appeal of a Hallmark card: perhaps aged males return to their natal troop, their hometown, to spend their final years in the care of their aged sisters and other female relatives. Another theory suggests that aged males may leave the troop in which they spent their prime when their daughters reach reproductive age, so as not to breed with them inadvertently. A particularly odd twist on this idea comes from studies of the sifaka, a Madagascan primate. In a combination of King Lear and bad Marlin Perkins, it seems, the reproductive-age females drive out the elderly fathers. No Hallmark cards there for Father’s Day.

The data from my baboons suggest an additional reason for the occasional transfer of an aged male. In many ways, the last thing you’d ever want to do is spend your older years in the troop in which you spent your prime--because the current gang in charge treats you horribly.

When you examine dominance interactions among the individuals in a troop, a distinctive pattern emerges. High-ranking males have their tense interactions with each other--one will force another to give up a piece of food or a resting spot, or will disrupt grooming or sexual behavior. Typically number 3 in the hierarchy will have his most frequent interactions with number 2--breathing down his neck, hoping to ratchet himself up a step in the pecking order by delivering a knockout punch--and with number 4, who is trying to do the same to him. Meanwhile, these high- ranking tusslers seldom bother with lowly number 20, a puny adolescent newcomer (unless they are having a particularly bad day and need someone small to take it out on).

Inspect the matrix of interactions, though, and an odd element will jump out of the pattern: the highest-ranking males, besides testing each other, will be having a zillion dominance interactions with seemingly insignificant number 14. Who is he? Why is his nose being so roundly rubbed in his subordinacy? Elderly number 14, it turns out, used to be number 1, back when he was in his prime and the current dominant males were squirrelly adolescents. And they remember. When I examined the few males who had transferred into my troop in their old age, they all experienced the same new world. They were utterly subordinate, sitting in the cellar of the hierarchy, but at least they were anonymous and ignored. The males who spent their twilight years with the troop in which they’d spent their prime, however, were subject to more than twice as many dominance interactions as the old anonymous males who had transferred in.

Why are the prime-age males so aggressive to the deposed ruling class? Are they afraid that the old guys may rise again? Do they get an ugly thrill from getting away with it? It’s impossible, of course, to say what’s going on in their heads. My data indicate, however, that the new generation doesn’t care who the aged animal is, so long as he was once high-ranking. In theory, one might have expected what goes around to come around--males who were particularly brutal in their prime should be the ones most subject to the indignities of old age. But I did not observe that pattern; the brutalizing of elderly males who remained in the troop was independent of how aggressively they had behaved in their heyday. Apparently all that mattered was that they had once been dominant and that they no longer were.

It seems rather sad to me that, among our close relatives, the elderly may be better off taking their chances with the lions instead of with their own species. But looking at this grim pattern, my earlier puzzlement--Why should an elderly male ever leave the troop?--gives rise to the inverse: Why should he ever stay? Yet roughly half of them do, living out their final years in the troop in which they spent their prime. Have these males held on to a protective high rank longer? No, suggested my data. Instead, they have something unique to sustain them during the hard times--friendship.

Aging, it has been said, is a time of life spent among strangers. In our society, women tend to outlive their husbands, while men all too often outlive their perceived roles--breadwinner, careerist--only to discover that they never made any true intimates along the way. Studies have shown how much more readily women make friends than men. Women communicate better in general and about emotions in particular. They’re apt to view cooperation and interdependence as a goal rather than as a sign of weakness; they’re more interested in affirming one another’s problems emotionally than in simply solving them. By old age, women and men differ dramatically in the number of friends and intimates they still have. Psychologists have shown that for an older man, having close friends is physiologically protective, while for women, the quality of the close friendship is the important part. Having intimate friends is so rare for an older man that it’s a salutary marker in itself. For an aged woman, though, intimate friends are so much the norm that it is the more subtle quality of the friendship that makes the difference.

There are some parallels here to the world of baboons. Females, because they spend their whole lives in the same troop, are surrounded by relatives and nonrelatives with whom they’ve had decades to develop relationships. Moreover, social rank in females is hereditary and, for the most part, static over a lifetime, so jostling for higher rank is not a feature in a female’s life. Males, however, typically spend their adult years apart from relatives and the individuals they grew up with, and the primary focus of their social interactions is often male-male competition. In such a world, it is a rare male who has friends.

To use this term is not anthropomorphism. Male baboons do not have male friends. I can count on one hand the number of times I’ve seen adult males grooming one another over the years. The most a male can generally hope for from another adult male is a temporary business partnership in a coalition, and often an uneasy one at that. When males form friendships, it is with females.

This has nothing to do with sex--it’s purely platonic, independent of where the female is in her reproductive cycle. He and she are just friends. She is an individual whom the male grooms a lot and who grooms him in return. He sits touching her when either is troubled by some tumult in the baboon world and plays with her infant or carries it protectively when a predator lurks.

Primatologist Barbara Smuts, of the University of Michigan, published a superb monograph a decade ago analyzing the rewards and heartbreaks of baboon friendships, trying to make sense of which males are capable of such stability. She documented something that I know many baboonologists have observed in their animals: males who develop friendships are ones who have placed a high priority on them throughout their prime adult years. These are males who would put more effort into forming friendly affiliations with females than into making strategic fighting coalitions with other males. These are the baboons who maximize reproductive success through covert matings with females who prefer them, rather than through the overt matings that are the rewards of successful male-male conflict. These males, in the prime of life, might even have walked away from high rank, voluntarily relinquishing dominant positions, to avoid being decisively defeated (and possibly crippled) when they came to their Waterloo.

Work by Smuts and others has shown that male baboons become more likely to form such affiliations with females as they mellow into old age. But, to infest the world of baboons with some psychobabble, the males with the highest rates of these affiliative behaviors are the ones who made their distinctive life-style choices early on, and this establishing of priorities is what differentiates them in their old age. When I compared males who remained in the same troop in their later years with those who left, the former were the ones with the long-standing female friendships-- still mating, grooming, being groomed, sitting in contact with females, interacting with infants. These are the males who have worked to become part of a community.

Many gerontologists today emphasize successful aging--how a surprisingly large number of individuals spend their later years healthy, satisfied, and productive. This work is a pleasing antidote to the view of aging as nothing but the dying of the light. Of course, many factors that affect how successfully an individual ages, from genes to socioeconomic status, can depend on luck. Yet gerontologists are coming to see that successful aging also reflects how you live your daily life even before reaching the threshold of old age. In this realm, quick medical fixes won’t help, nor will spates of resolutions about eating right, relaxing more, and getting some exercise starting first thing tomorrow. Many health care professionals are concerned about the difficulty humans have performing the small, incremental daily acts that constitute good preventive medicine; it seems that when it comes to taking the small steps needed to build lifelong affiliations, your average male baboon isn’t very good at it, either. But the consequences for those who are appear to be considerable. There’s a world of difference between doing things today and planning to do them tomorrow.

Somewhere, no doubt, there is a warehouse crammed with unsold, musty merchandise left over when various fads of the 1960s faded--cartons of cranberry-striped bell-bottoms, case upon case of love beads. Among them may be some of those horribly clichéd posters about today being the first day of the rest of your life. There may still be a market for some of that stuff. Perhaps some baboons could use them.
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