... Human nature is a product of culture, but culture is also a product of human nature, and both are the products of evolution. This does not mean that I am going to argue that it is “all in our genes.” Far from it. I am vigorously going to challenge the notion that anything psychological is purely genetic, and equally vigorously challenge the assumption that anything universally human is untainted by genes. But our “culture” does not have to be the way it is. Human culture could be very much more varied and surprising than it is. Our closest relatives, the chimpanzees, live in promiscuous societies in which females seek as many sexual partners as possible and a male will kill the infants of strange females with whom he has not mated. There is no human society that remotely resembles this particular pattern. Why not? Because human nature is different from chimp nature.

If this is so, then the study of human nature must have profound implications for the study of history, sociology, psychology, anthropology, and politics. Each of those disciplines is an attempt to understand human behavior, and if the underlying universals of human behavior are the product of evolution, then it is vitally important to understand what the evolutionary pressures were. Yet I have gradually come to realize that almost all of social science proceeds as if 1859, the year of the publication of the Origin of Species, had never happened; it does so quite deliberately, for it insists that human culture is a product of our own free will and invention. Society is not the product of human psychology, it asserts, but vice versa.

That sounds reasonable enough, and it would be splendid for those who believe in social engineering if it were true, but it is simply not true. ...

Just as parasites depend on their hosts and yet make them suffer, and just as animals exploit their mates and yet need them, so the Red Queen never appears without another theme being sounded: the theme of intermingled cooperation and conflict. The relationship between a mother and her child is fairly straightforward: Both are seeking roughly the same goal—the welfare of themselves and each other. The relationship between a man and his wife’s lover or between a woman and her rival for a promotion is also fairly straightforward: Both want the worst for each other. One relationship is all about cooperation, the other all about conflict. But what is the relationship between a woman and her husband? It is cooperation in the sense that both want the best for the other. But why? In order to exploit each other. A man uses his wife to produce children for him. A woman uses her husband to make and help rear her children. Marriage teeters on the line between a cooperative venture and a form of mutual exploitation—ask any divorce lawyer. Successful marriages so submerge the costs under mutual benefits that the cooperation can predominate; unsuccessful ones do not.

This is one of the great recurring themes of human history, the balance between cooperation and conflict. It is the obsession of governments and families, of lovers and rivals. It is the key to economics. It is, as we shall see, one of the oldest themes in the history of life, for it is repeated right down to the level of the gene itself. And the principal cause of it is sex. Sex, like marriage, is a cooperative venture between two rival sets of genes. Your body is the scene of this uneasy coexistence.

There has been no genetic change since we were hunter-gatherers, but deep in the mind of the modern man is a simple male hunter-gatherer rule: Strive to acquire power and use it to lure women who will bear heirs; strive to acquire wealth and use it to buy other men’s wives who will bear bastards. It began with a man who shared a piece of prized fish or honey with an attractive neighbor’s wife in exchange for a brief affair and continues with a pop star ushering a model into his Mercedes. From fish to Mercedes, the history is unbroken: via skins and beads, plows and cattle, swords and castles. Wealth and power are means to women; women are means to genetic eternity.

Likewise, deep in the mind of a modern woman is the same basic hunter-gatherer calculator, too recently evolved to have changed much: Strive to acquire a provider husband who will invest food and care in your children; strive to find a lover who can give those children first-class genes. Only if she is very lucky will they be the same man. It began with a woman who married the best unmarried hunter in the tribe and had an affair with the best married hunter, thus ensuring her children a rich supply of meat. It continues with a rich tycoon’s wife bearing a baby that grows up to resemble her beefy bodyguard. Men are to be exploited as providers of parental care, wealth, and genes.

Cynical? Not half as cynical as most accounts of human history.

If I am right and people are just animals with more than usually trainable instincts, then it might seem that I am excusing instinctive behavior. When a man kills another man or tries to seduce a woman, he is just being true to his nature. What a bleak, amoral message. Surely there is a more natural basis for morality in the human psyche than that? The centuries-old debate between the followers of Rousseau and Hobbes—whether we are corrupted noble savages or civilized brutes—has missed the point. We are instinctive brutes, and some of our instincts are unsavory. Of course some instincts are very much more moral, and the vast human capacity for altruism and generosity—the glue that has always held society together—is just as natural as any selfishness. Yet selfish instincts are there, too. Men are much more instinctively capable of murder and of sexual promiscuity than women, for example. But Hobbes’s vindication means nothing because instincts combine with learning. None of our instincts is inevitable; none is insuperable. Morality is never based upon nature. It never assumes that people are angels or that the things it asks human beings to do come naturally. “Thou shalt not kill” is not a gentle reminder but a fierce injunction to men to overcome any instincts they may have or face punishment.

... Some of the best arguments, such as Fisher’s theory of runaway sexual selection, are circular. The relationship between chickens and eggs is circular. Miller is actually rather proud of the theory’s circularity because he believes we have learned from computer simulation that evolution is a process which pulls itself up by its bootstraps. There is no single cause and effect because effects can reinforce causes. If a bird finds itself to be good at cracking seeds, then it specializes in cracking seeds, which puts further pressure on its seed-cracking ability to evolve.

Evolution is circular. It is a disquieting thought that our heads contain a neurological version of a peacock’s tail—an ornament designed for sexual display whose virtuosity at everything from calculus to sculpture is perhaps just a side effect of the ability to charm. Disquieting and yet not altogether convincing. The sexual selection of the human mind is the most speculative and fragile of the many evolutionary theories discussed in this book, but it is also very much in the same vein as the others. I began this book by asking why all human beings were so similar and yet so different, suggesting that the answer lay in the unique alchemy of sex. An individual is unique because of the genetic variety that sexual reproduction generates in its perpetual chess tournament with disease. An individual is a member of a homogeneous species because of the incessant mixing of that variety in the pool of fellow human beings’ genes. And I end with one of the strangest of the consequences of sex: that the choosiness of human beings in picking their mates has driven the human mind into a history of frenzied expansion for no reason except that wit, virtuosity, inventiveness, and individuality turn other people on. ...

Mankind is a self-domesticated animal; a mammal; an ape; a social ape; an ape in which the male takes the initiative in courtship and females usually leave the society of their birth; an ape in which men are predators, women herbivorous foragers; an ape in which males are relatively hierarchical, females relatively egalitarian; an ape in which males contribute unusually large amounts of investment in the upbringing of their offspring by provisioning their mates and their children with food, protection, and company; an ape in which monogamous pair bonds are the rule but many males have affairs and occasional males achieve polygamy; an ape in which females mated to low-ranking males often cuckold their husbands in order to gain access to the genes of higher-ranking males; an ape that has been subject to unusually intense mutual sexual selection so that many of the features of the female body (lips, breasts, waists) and the mind of both sexes (songs, competitive ambition, status seeking) are designed for use in competition for mates; an ape that has developed an extraordinary range of new instincts to learn by association, to communicate by speech, and to pass on traditions. But still an ape.

Half the ideas in this book are probably wrong. ...