Why do men want to be rich, powerful and successful? It sounds a silly question, but if science were always satisfied with the obvious we'd never have got past Aristotle. Before Galileo, it was obvious that light objects fall more slowly than heavy. Before Darwin, all sorts of things were obvious, among them the 'commonsense' fact that men want to be rich and powerful. But Darwinian selection works only to preserve genes, and riches and fame don't obviously yield genetic gains. So there really is a question. To approach the answer, we turn to the White House. 

When Bill Clinton squares up to Saddam Hussein, one man has his hand behind his back, fending off a squeaking, yapping pack of bimbos, lawyers and both. It is his ironic misfortune to live in a culture that sees as a crime actions which, in his opponent's culture, would be self-evident grounds for praise and envy. To appreciate the absurdity of the situation, try to imagine a CIA plot to discredit Saddam Hussein by implicating him in multiple affairs with women. It could do nothing but gain him prestige. In this respect, if no other, Islam shows some understanding of Darwinian realities. 

Darwinism is all about genes surviving in populations. Genes that build the present generation survived through past generations. The Darwinian insight follows: the genes that build the present generation were well qualified to survive in ancestral worlds. To the extent that the present resembles the past, today's genes will do well in the present. This is why, as a convention, Darwinians interpret behaviour as 'aimed' at the future 'goal' of survival and reproduction. But it is only a convention. The fact is only that all creatures are built by genes that succeeded in building ancestors. If present conditions depart from ancestral conditions, individuals will behave in ways not well calculated to assist their genes. 

In the excessive quantities that many of us enjoy it, sugar is a slow poison. So why do we overeat the stuff? Because through most of our ancestral history it was impossible to procure more than the small doses in which sugar is good for you. People who liked sugar became ancestors, and it is from ancestors that we get our genes. So we like sugar whenever we can get it - and suffer dental caries and diabetes. 

We lust, because our ancestors' lust helped pass their lustful genes on to us. Here, as it happens, Darwinism agrees with commonsense: the convention works. But sometimes the convention breaks down. If we are on the Pill, or know that our sexual partner is, it doesn't diminish our desire. We still inherit the ancient rule of thumb, now out of date. As Steven Pinker 
says, in his splendid book How the Mind Works, "Had the Pleistocene contained trees bearing birth-control pills, we might have evolved to find them as terrifying as a venomous spider." 

Genetic effects are often conditional. Genes have an 'IF Statement' in their programming. Sex chromosomes apart, our genes have inhabited as many female ancestors as male, and the best way for a gene to survive in the two conditions is different. "IF you find yourself in a male body build a penis, otherwise build a clitoris." "IF you find yourself in a female body, build bigger breasts." 

In species like seals and deer, where males hold large harems, it is easier for a male than for a female to become a wildly successful reproducer, but easier for a female to become a reproducer at all. Harem-holding males pass a disproportionate share of genes on to the future, which leaves other males passing none. Females are mostly harem members and their reproductive success is middling, between the male extremes. Most individuals are descended from a long line of harem-owning males and an equally long line of harem-belonging females. We can therefore expect IF Statements that read: "If you find yourself in a male body, assume that it is a member of the elite, or work hard to make it so." Modern males might be particularly aggressive, because past males that fought fiercely won harems and became ancestors. Females became ancestors whether they won fights or not. A male's offspring count is highly correlated with his mate count. For all sorts of reasons (for instance ,while pregnant you can't get pregnant again) the same is less true of a female. 

Not all species are like seals and deer. Some form monogamous pairs. The difference is an economic one. 'Wealth' (for example being a big 'landowner' as in a male bird who successfully defends a large territory) is attractive to females because wealth translates into offspring survival. Species whose food supplies, or other important goods like nesting territories, are easily monopolisable, tend to become 'polygynous' (rich males hold harems of females forcing poor males to be celibate). There is a 'polygyny threshold', a threshold level of wealth inequality, at which a female is marginally better off as the second wife of a rich male than she would be as the only wife of a poor male. In species with the possibility of extreme wealth-inequality, very large harems are built up by very few males. Monogamous mating systems typify species whose economic goods are by their nature difficult to hog. Even the richest male is not so different from the poorest as to tempt a female to become his second wife. 

And what of humans? Did our wild African ancestors live in harems like seals and deer? Or are we, like many songbirds, among nature's monogamists? Indirect clues suggest a leaning towards the harem. First, men tend to be larger than women, a pattern unsurprisingly typical of polygynous mammals. Second, a worldwide ethnographic survey of 849 human 
societies showed 708 whose customs are polygynous (more than one wife), four polyandrous (more than one husband) and 137 monogamous. Third, psychological evidence shows males typically seeking sexual variety, attracted by physical indicators of female fecundity such as youth and blooming health; while females are drawn to indicators of male wealth or 
wealth-gaining potential, including power - Henry Kissinger's 'ultimate aphrodisiac.' 

The Darwinian anthropologist Napoleon Chagnon has made a lifelong study of the Yanomamo of the Amazon jungle, one of the few tribes that retain our ancestral hunter-gatherer way of life. The Yanomamo call themselves 'the fierce people', and violent and lethal fighting is rife. To quote the distinguished biologist E.O.Wilson, "One quarter of all Yanomamo men die in battle, but the surviving warriors are often wildly successful in the game of reproduction. The founder of one bloc of villages had forty-five children by eight wives. His sons were also prolific, so that approximately 75% of all of the sizable population in the village bloc were his descendants." When Chagnon asked a Yanomamo man why they fought, the question provoked astonishment: "What? Don't ask such a stupid question! It is women! Women! We fight over women!" 

The Darwinian historian Laura Betzig has shown that, both in the Roman Empire and in medieval Christendom, though marriage was monogamous, mating was often polygynous. A Lord of the Manor would have one wife. But his household was set up as an unofficial harem of servant girls and other lower-class young women who found in the manor a haven from poverty. The 13th Century Count Baudoin was typical in siring 23 bastards. His bedchamber "had access to the servant girls' quarters, and to the rooms of adolescent girls upstairs. It had access, too, to the warming room, 'a 
veritable incubator for the suckling infants'." In the 12th century, Giselbert of Mons found it 'risible' that a certain count, in spite of his opportunities, was faithful to his wife. The monasteries were also big landowners, and Betzig unearths parallel accounts of the sexual exploits of their abbots and monks. 

In our society we think of lifelong monogamy as the norm, or at least the ideal. A numerical majority of societies of the world, past and present, might think it aberrant, and it is plausible that our wild ancestors would have responded to Clinton's predicament - having to defend himself against a charge of consorting with several women - with open-mouthed incredulity. What else does a man become a great chieftain for? (Yes, yes, I know Clinton is officially accused of lying about it rather than doing it, but our ancestors would have laughed just as much at the social mores that make it necessary for a great chief to lie about such things). If John F. Kennedy really copulated with as many women as is now claimed, including the widely coveted Marylin Monroe, our ancestors would have expected nothing less of so illustrious a chief. As for Lloyd George . . . 

I must throw in the usual health-warning. 'Is' does not mean 'ought'. I do not long to return to ancestral ways. I'd hate to live in a hunter-gatherer world where men fight over women, or in any polygynous culture where a woman is a man's chattel rather than companion or colleague. With pleasure I take the un-Darwinian personal decision to live as a deliberately monogamous individual. But I am not happy to live in a sanctimonious, lawyer-driven society that tries to bring down a man for doing in private what many men would secretly emulate if they had his opportunities. 

Of course I find something unpleasant in the abuse of power over employees and underlings. But, once again, that is a western, modern perception of what is going on, something that would provoke hoots of derision from Clinton's Arab opponents. As for the charge of mendacity, by all means let us have leaders that are truthful in great affairs of state. But in small affairs that are the business only of a man, his wife, and the other individuals involved, it is a prying society that compels him to lie by not allowing him to say "That is none of your business." Ironically it becomes society's legitimate business only when, as in Profumo's case, sexual indiscretion compromises state secrets and threatens to expose lies told in the interests of national security. 

To return to our opening question, why do men strive to become rich and powerful, instead of concentrating on reproduction like good Darwin machines? 'Instead' arises only in an eccentric minority of societies. Wealth, power and worldly success once translated directly into wives and grandchildren, and in many societies they still do. But in our society they are pursued in their own right alone, like the taste for unlimited sugar long after the translation rules have changed. Men today seek wealth and power because wealth and power among our ancestors, in all kinds of direct and indirect ways, bought genetic survival. The rule of thumb has outlived its Darwinian usefulness. Bill Clinton is a beached tribal chief, washed high and dry in the land of lawyers.