This paradox suggests that something other than the best interests of his wife and children lie behind an Aché man’s preference for big-game hunting. As Kristen Hawkes described these paradoxes to me, I developed an awful foreboding that the true explanation might prove less noble than the male’s mystique of bringing home the bacon. I began to feel defensive on behalf of my fellow men and to search for explanations that might restore my faith in the nobility of the male strategy.
My first objection was that Kristen Hawkes’s calculations of hunting returns were measured in calories. In reality, any nutritionally aware modern reader knows that not all calories are equal. Perhaps the purpose of big-game hunting lies in fulfilling our need for protein, which is more valuable to us nutritionally than the humble carbohydrates of palm starch. However, Aché men target not only protein-rich meat but also honey, whose carbohydrates are every bit as humble as those of palm starch. While Kalahari San men (“Bushmen”) are hunting big game, San women are gathering and preparing mongongo nuts, an excellent protein source. While lowland New Guinea hunter-gatherer men are wasting their days in the usually futile search for kangaroos, their wives and children are predictably acquiring protein in the form of fish, rats, grubs, and spiders. Why don’t San and New Guinea men emulate their wives?
I next began to wonder whether Aché men might be unusually ineffective hunters, an aberration among modern hunter-gatherers. Undoubtedly, the hunting skills of Inuit (Eskimo) and Arctic Indian men are indispensable, especially in winter, when little food other than big game is available. Tanzania’s Hadza men, unlike the Aché, achieve higher average returns by hunting big game rather than small game. But New Guinea men, like the Aché, persist in hunting even though yields are very low. And Hadza hunters persist in the face of enormous risks, since on the average they bag nothing at all on twenty-eight out of twenty-nine days spent hunting. A Hadza family could starve while waiting for the husband-father to win his gamble of bringing down a giraffe. In any case, all that meat occasionally bagged by a Hadza or Aché hunter isn’t reserved for his family, so the question of whether big-game hunting yields higher or lower returns than alternative strategies is academic from his family’s point of view. Big-game hunting just isn’t the best way to feed a family.
Still seeking to defend my fellow men, I then wondered: could the purpose of widely sharing meat and honey be to smooth out hunting yields by means of reciprocal altruism? That is, I expect to kill a giraffe only every twenty-ninth day, and so does each of my hunter friends, but we all go off in different directions, and each of us is likely to kill his giraffe on a different day. If successful hunters agree to share meat with each other and their families, all of them will often have full bellies. By that interpretation, hunters should prefer to share their catch with the best other hunters, from whom they are most likely to receive meat some other day in return.
In reality, though, successful Aché and Hadza hunters share their catch with anyone around, whether he’s a good or hopeless hunter. That raises the question of why an Aché or Hadza man bothers to hunt at all, since he can claim a share of meat even if he never bags anything himself. Conversely, why should he hunt when any animal that he kills will be shared widely? Why doesn’t he just gather nuts and rats, which he can bring to his family and would not have to share with anyone else? There must be some ignoble motive for male hunting that I was overlooking in my efforts to find a noble motive.
As another possible noble motive, I thought that widespread sharing of meat helps the hunter’s whole tribe, which is likely to flourish or perish together. It’s not enough to concentrate on nourishing your own family if the rest of your tribe is starving and can’t fend off an attack by tribal enemies. This possible motive, though, returns us to the original paradox: the best way for the whole Aché tribe to become well nourished is for everybody to humble themselves by pounding good old reliable palm starch and collecting fruit or insect larvae. The men shouldn’t waste their time gambling on the occasional peccary.
In a last effort to detect family values in men’s hunting, I reflected on hunting’s relevance to the role of men as protectors. The males of many territorial animal species, such as songbirds, lions, and chimpanzees, spend much time patrolling their territories. Such patrols serve multiple purposes: to detect and expel intruding rival males from adjacent territories; to observe whether adjacent territories are in turn ripe for intrusion; to detect predators that could endanger the male’s mate and offspring; and to monitor seasonal changes in abundance of foods and other resources. Similarly, at the same time as human hunters are looking for game, they too are attentive to potential dangers and opportunities for the rest of the tribe. In addition, hunting provides a chance to practice the fighting skills that men employ in defending their tribe against enemies.
This role of hunting is undoubtedly an important one. Nevertheless, one has to ask what specific dangers the hunters are trying to detect, and whose interests they are thereby trying to advance. While lions and other big carnivores do pose dangers to people in some parts of the world, by far the greatest danger to traditional hunter-gatherer human societies everywhere has been posed by hunters from rival tribes. Men of such societies were involved in intermittent wars, the purpose of which was to kill men of other tribes. Captured women and children of defeated rival tribes were either killed or else spared and acquired as wives and slaves, respectively. At worst, patrolling groups of male hunters could thus be viewed as advancing their own genetic self-interest at the expense of rival groups of men. At best, they could be viewed as protecting their wives and children, but mainly against the dangers posed by other men. Even in the latter case, the harm and the good that adult men bring to the rest of society by their patrolling activities would be nearly equally balanced.
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Thus, all five of my efforts to rescue Aché big-game hunting as a sensible way for men to contribute nobly to the best interests of their wives and children collapsed. Kristen Hawkes then reminded me of some painful truths about how an Aché man himself (as opposed to his wife and kids) gets big benefits from his kills besides the food entering his stomach.
To begin with, among the Aché, as among other peoples, extramarital sex is not uncommon. Dozens of Aché women, asked to name the potential fathers (their sex partners around the time of conception) of 66 of their children, named an average of 2.1 men per child. Among a sample of 28 Aché men, women named good hunters more often than poor hunters as their lovers, and they named good hunters as potential fathers of more children.
To understand the biological significance of adultery, recall that the facts of reproductive biology discussed in chapter 2 introduce a fundamental asymmetry into the interests of men and women. Having multiple sex partners contributes nothing directly to a woman’s reproductive output. Once a woman has been fertilized by one man, having sex with another man cannot lead to another baby for at least nine months, and probably for at least several years under hunter-gatherer conditions of extended lactational amenorrhea. In just a few minutes of adultery, though, an otherwise faithful man can double the number of his own offspring.
Now compare the reproductive outputs of men pursuing the two different hunting strategies that Hawkes terms the “provider” strategy and the “show-off” strategy. The provider hunts for foods yielding moderately high returns with high predictability, such as palm starch and rats. The show-off hunts for big animals; by scoring only occasional bonanzas amid many more days of empty bags, his mean return is lower. The provider brings home on the average the most food for his wife and kids, although he never acquires enough of a surplus to feed anyone else. The show-off on the average brings less food to his wife and kids but does occasionally have lots of meat to share with others.
Obviously, if a woman gauges her genetic interests by the number of children whom she can rear to maturity, that’s a function of how much food she can provide them, so she is best off marrying a provider. But she is further
well served by having show-offs as neighbors, with whom she can trade occasional adulterous sex for extra meat supplies for herself and her kids. The whole tribe also likes a show-off because of the occasional bonanzas that he brings home for sharing.
As for how a man can best advance his own genetic interests, the show-off enjoys advantages as well as disadvantages. One advantage is the extra kids he sires adulterously. The show-off also gains some advantages apart from adultery, such as prestige in his tribe’s eyes. Others in the tribe want him as a neighbor because of his gifts of meat, and they may reward him with their daughters as mates. For the same reason, the tribe is likely to give favored treatment to the show-off’s children. Among the disadvantages to the show-off are that he brings home on the average less food to his own wife and kids; this means that fewer of his legitimate children may survive to maturity. His wife may also philander while he is doing so, with the result that a lower percentage of her children are actually his. Is the show-off better off giving up the provider’s certainty of paternity of a few kids, in return for the possibility of paternity of many kids?
The answer depends on several numbers, such as how many extra legitimate kids a provider’s wife can rear, the percentage of a provider’s wife’s kids that are illegitimate, and how much a show-off’s kids find their chances of survival increased by their favored status. The values of these numbers must differ among tribes, depending on the local ecology. When Hawkes estimated the values for the Aché, she concluded that, over a wide range of likely conditions, show-offs can expect to pass on their genes to more surviving children than can providers. This purpose, rather than the traditionally accepted purpose of bringing home the bacon to wife and kids, may be the real reason behind big-game hunting. Aché men thereby do good for themselves rather than for their families.
Thus, it is not the case that men hunters and women gatherers constitute a division of labor whereby the nuclear family as a unit most effectively promotes its joint interests, and whereby the work force is selectively deployed for the good of the group. Instead, the hunter-gatherer lifestyle involves a classic conflict of interest. As I discussed in chapter 2, what’s best for a man’s genetic interests isn’t necessarily best for a woman’s, and vice versa. Spouses share interests, but they also have divergent interests. A woman is best off married to a provider, but a man is not best off being a provider.
Biological studies of recent decades have demonstrated numerous such conflicts of interest in animals and humans—not only conflicts between husbands and wives (or between mated animals), but also between parents and children, between a pregnant woman and her fetus, and between siblings. Parents share genes with their offspring, and siblings share genes with each other. However, siblings are also potentially each other’s closest competitors, and parents and offspring also potentially compete. Many animal studies have shown that rearing offspring reduces the parent’s life expectancy because of the energy drain and risks that the parent incurs. To a parent, an offspring represents one opportunity to pass on genes, but the parent may have other such opportunities. The parent’s interests may be better served by abandoning one offspring and devoting resources to other offspring, whereas the offspring’s interests may be best served by surviving at the expense of its parents. In the animal world as in the human world, such conflicts not infrequently lead to infanticide, parricide (the murder of parents by an offspring), and siblicide (the murder of one sibling by another). While biologists explain the conflicts by theoretical calculations based on genetics and foraging ecology, all of us recognize them from experience, without doing any calculations. Conflicts of interest between people closely related by blood or marriage are the commonest, most gut-wrenching tragedies of our lives.
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What general validity do these conclusions possess? Hawkes and her colleagues studied just two hunter-gatherer peoples, the Aché and the Hadza. The resulting conclusions await testing of other hunter-gatherers. The answers are likely to vary among tribes and even among individuals. From my own experience in New Guinea, Hawkes’s conclusions are likely to apply even more strongly there. New Guinea has few large animals, hunting yields are low, and bags are often empty. Much of the catch is consumed directly by the men while off in the jungle, and the meat of any big animal brought home is shared widely. New Guinea hunting is hard to defend economically, but it brings obvious payoffs in status to successful hunters.
What about the relevance of Hawkes’s conclusions to our own society? Perhaps you’re already livid because you foresaw that I’d raise that question, and you’re expecting me to conclude that American men aren’t good for much. Of course that’s not what I conclude. I acknowledge that many (most? by far the most?) American men are devoted husbands, work hard to increase their income, devote that income to their wives and kids, do much child care, and don’t philander.
But, alas, the Aché findings are relevant to at least some men in our society. Some American men do desert their wives and children. The proportion of divorced men who renege on their legally stipulated child support is scandalously high, so high that even our government is starting to do something about it. Single parents outnumber coparents in the United States, and most single parents are women.
Among those men who remain married, all of us know some who take better care of themselves than of their wives and children, and who devote inordinate time, money, and energy to philandering and to male status symbols and activities. Typical of such male preoccupations are cars, sports, and alcohol consumption. Much bacon isn’t brought home. I don’t claim to have measured what percentage of American men rate as show-offs rather than providers, but the percentage of show-offs appears not to be negligible.
Even among devoted working couples, time budget studies show that American working women spend on the average twice as many hours on their responsibilities (defined as job plus children plus household) as do their husbands, yet women receive on the average less pay for the same job. When American husbands are asked to estimate the number of hours that they and their wives each devote to children and household, the same time budget studies show that men tend to overestimate their own hours and to underestimate their wife’s hours. It’s my impression that men’s household and child-care contributions are on the average even lower in some other industrialized countries, such as Australia, Japan, Korea, Germany, France, and Poland, to mention just a few with which I happen to be familiar. That’s why the question what men are good for continues to be debated within our societies, as well as between anthropologists.
CHAPTER 6
MAKING MORE BY MAKING LESS
The Evolution of Female Menopause
Most wild animals remain fertile until they die, or until close to that time. So do human males: although some men become infertile or less fertile at various ages for various reasons, men experience no universal shutdown of fertility at any particular age. There are innumerable well-attested cases of old men, including a ninety-four-year-old, fathering children.
But human females undergo a steep decline in fertility from around age forty, leading to universal complete sterility within a decade or so. While some women continue to have regular menstrual cycles up to the age of fifty-four or fifty-five, conception after the age of fifty was rare until the recent development of medical technologies using hormone therapy and artificial fertilization. For example, among the American Hutterites, a strict religious community that is well nourished and opposed to contraception, women produce babies as fast as is biologically possible for humans, with a mean interval of only two years between births, and a mean final number of eleven children. Even Hutterite women stop producing babies by age forty-nine.
To laypeople, menopause is an inevitable fact of life, albeit often a painful one anticipated with foreboding. But to evolutionary biologists, human female menopause is an aberration in the animal world and an intellectual paradox. The essence of natural selection is that it promotes genes for traits that increas
e the number of one’s descendants bearing those genes. How could natural selection possibly result in every female member of a species carrying genes that throttle her ability to leave more descendants? All biological traits are subject to genetic variation, including the age of human female menopause. Once female menopause somehow became fixed in humans for whatever reason, why did not its age of onset gradually become pushed back until it disappeared again, because those women who experienced menopause later in life left behind more descendants?
To evolutionary biologists, female menopause is thus among the most bizarre features of human sexuality. As I shall argue, it is also among the most important. Along with our big brains and upright posture (emphasized in every text of human evolution), and our concealed ovulations and penchant for recreational sex (to which texts devote less attention), I believe that female menopause was among the biological traits essential for making us distinctively human—a creature more than, and qualitatively different from, an ape.
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Many biologists would balk at what I have just said. They would argue that human female menopause does not pose an unsolved problem, and that there is no need to discuss it further. Their objections are of three types.
First, some biologists dismiss human female menopause as an artifact of a recent increase in human expected life span. That increase stems not just from public health measures within the last century but possibly also from the rise of agriculture ten thousand years ago, and even more likely from evolutionary changes leading to increased human survival skills within the last forty thousand years. According to this view, menopause could not have been a frequent occurrence for most of the several million years of human evolution, because (supposedly) almost no women or men survived past the age of forty. Of course, the female reproductive tract was programmed to shut down by age forty, because it would not have had the opportunity to operate thereafter anyway. The increase in human life span has developed much too recently in our evolutionary history for the female reproductive tract to have had time to adjust—so goes this objection.
Why Is Sex Fun?: The Evolution of Human Sexuality Page 10