by Robin Baker
Since women are seeking different attributes in short-term and long-term partners, but have more choice of short-term, they may again have to compromise. They have two main options. They can choose the best available long-term partner, and then rely on infidelity to obtain the best genes. This can succeed, but only if they successfully avoid the disadvantages of infidelity that we have already discussed (Scenes 8 to 11). Alternatively, they can choose a man who, although neither the best provider of genes nor the best partner, is at least the best available compromise.
As we have found in so many aspects of reproductive success, women’s behaviour and experience are mirrored by other animals. In this instance, women are not the only females who have to trade off between male support and male genes. One of the most revealing studies of the problem concerns a bird, the blue tit. The females of this species show all of the behaviour we have just described for women. Those lucky ones paired to genetically superior males with the best territories are totally faithful. Neighbouring females, paired to genetically inferior males, take every opportunity to seek infidelity with the superior males. They sneak into the better males’ territories, solicit intercourse, then return unobserved to the partner they have just cheated. On average, about a third of young birds in a nest have not been sired by their mother’s partner. Actual levels range from 0 per cent in the nests of the most favoured males to about 80 per cent in the nests of the least favoured ones.
A surprisingly similar pattern is found in humans. On average, about 10 per cent of children are not sired by their supposed father. Some men, however, have a higher chance of being deceived in this way than others – and it is those of low wealth and status who fare worst. Actual figures range from 1 per cent in high-status areas of Switzerland and the USA, through 5-6 per cent for moderate-status males in Britain and the USA, to 10-30 per cent for lower-status males in Britain, France and the USA. Moreover, the men most likely to sexually hoodwink the lower-status males are men of higher status. Anthropological studies have shown precisely the same pattern. Men of higher wealth and status obtain partners earlier, start to reproduce earlier, are less likely to have their partners impregnated by other men and are more likely to do exactly that to other males. So in all ways, men of wealth and status have the potential to be reproductively more successful than their lower-status contemporaries.
Returning to birds – it is rare, unless the male is infertile, for all of the young in ‘his’ nest to have been sired by other males. It is as if the female always gives her partner some chance of paternity so as to retain his help in paternal care. The same may be true for humans. Moreover, when we look at which children are most likely to belong to their partner, women show a clear pattern. As with the woman in Scene 18, the child most likely to have been sired by a woman’s partner is the second; the children least likely are the first, and particularly the last. The reasons, though, are slightly different for first and last.
Often, a woman is already pregnant when she settles down with a long-term partner, and occasionally this partner is not the father of her child. Sometimes he knows this and takes on the woman and her child anyway (Scene 15), for reasons we have discussed (Scene 9), but sometimes he doesn’t know. The woman is least likely to be unfaithful in the weeks or months preceding the conception of her second child. Subsequent children, however, are more and more likely to be the product of infidelity.
Identifying the best partners and the best providers of genes, then pursuing the best available compromise, is only one aspect of a woman’s problem in obtaining a mate. Having selected him, she then has to recruit him into the chosen role. She can do this only if the man finds her attractive enough. If she cannot attract her first choice, she then has to compromise yet again. The man she finally recruits will be the best compromise among those she wants and those she can attract. The woman in Scene 18 was successful because a rich and successful man, thirty-five years older than herself, picked her out from the crowd. Then, without her infidelity being detected, she set about collecting genes from other successful men. She succeeded once again because these men considered sex with her to be worth the risk. In short, she succeeded because she was attractive to men, both as a partner and as a lover.
So, what was it about this woman that men found so attractive? What criteria do men use in choosing partners and lovers, and how do these criteria differ from those used by women?
Basically, men select women for their health, fertility and fidelity - though not consciously, of course. On seeing a woman, men do not immediately remark on her potential for bearing and raising children. Nevertheless, the features that men’s bodies are programmed to find attractive are precisely those that do reflect this potential. Unlike a woman, a man uses similar criteria whether he is selecting a partner or a lover – for both, his primary concern is with looks and behaviour. An important feature is body shape, particularly the ratio of waist to hip. Irrespective of whether a woman is thin or fat, men prefer someone whose waist measurement is about 70 per cent of her hip measurement. This preference is remarkably constant both throughout history (to judge from statues, paintings and ‘girlie’ magazines) and from culture to culture (to judge from rock-paintings and figurines). In some cultures, men prefer thin women; in others, fat. But in all cultures, they prefer women with waists significantly narrower than their buttocks. The explanation is that this shape reflects a good hormone balance, good resistance to disease and good fertility.
In addition to shape, men all over the world also respond strongly to clear eyes, healthy hair and skin, and the shape of the face, particularly its symmetry. Again, these features are strong indicators of health and hence fertility. Men of most cultures also respond to breast size and shape, though actual preferences vary and there is no simple link between the appearance of a woman’s breasts and her ability to lactate and sustain a child. Finally, men respond strongly to certain character traits, such as meekness and dependence, that might indicate potential fidelity. Such traits, though, are relatively easy to fake, at least for short periods.
There is another difference in mate preference between men and women. As long-term partners, women tend to prefer men who are older than themselves. Such men have had more time to prove themselves and more chance to amass the resources a woman will need to sustain any children she may have. Unless he is very wealthy, however, a man older than about fifty becomes less and less attractive to a younger, still fertile, woman – because of the increasing risk that he might die before any children she has with him become independent.
Men, on the other hand, prefer females who are old enough to be fertile, but still have most of their reproductive lives ahead of them. This way, they get more children from their investment. Whether a man is twenty or seventy, therefore, his preferred age for a new partner is about twenty, or even younger. Hence the frequency with which the most successful of men leave their middle-aged partner and their first family to set up home and begin a second family with a much younger woman.
An older but still fertile woman might also gain from a liaison with a younger man. This is because she can judge a man’s physical quality more easily when he is at his physical peak. But more often than not such a man is in no position to maintain an older woman, let alone her existing children and any new children their liaison might produce. Consequently, older women are most likely to target young men for acts of infidelity from within a secure long-term partnership, and are less likely to choose them as long-term partners.
The woman in Scene 18 had been freed from constraints by her personal wealth. She could have invited any of her ‘gardeners’ to live with her for a while and perhaps give her another child – they had all been carefully chosen for their genetic potential. She could undoubtedly have raised another child by such a man without prejudicing either her own health or the success of her existing children and future grandchildren. Nor need she have short-changed her new child. By the time we left the scene, the woman had not followed this co
urse, but she still had time to do so. Many rich women do.
Finally, once a woman is post-reproductive or once a man has ceased to be able to attract younger, fertile women (Scene 11), their criteria for mate choice change. Choice of a long-term partner can still influence their reproductive success, but now of course it is not via any children that they might produce together. It is instead via its effect on the survival and reproduction of any children they each may already have from a previous relationship (Scene 11). Wealth, status and the potential to be a good step-parent or stepgrandparent now become of primary importance to both sexes in their choice of a partner. All the same, most people still have to compromise.
We can see quite clearly that nowhere is the conflict of interests between males and females greater than in the selection and recruitment of a partner – at any age. Everybody is seeking the best partner in their preferred category, but may not themselves match up to that chosen person’s preferences. Competition is fierce. Everything is compromise, and time is limited. If a person settles too readily for a poor compromise, they may miss the chance of a much better compromise later. However, spending too long in search of the best compromise can be equally disadvantageous. He or she may then pay the price of having to settle for a worse compromise, or even of failing to attract anybody at all. The best prizes go to the people who judge correctly when to continue their search and when to settle for what they can get - if only for the time being.
There is a fascinating consequence of the criteria women use for mate selection – particularly their preference for, and greater fidelity to, men of wealth and status. The sons of such men achieve greater reproductive success than their lower-status contemporaries. They do this not only through their long-term relationships, but also because they have the same above-average opportunities to sire children with the partners of other men as did their fathers. It follows from this that a woman paired to such a man will achieve greater reproductive success if she produces sons than if she produces daughters.
The greatest number of children ever claimed by a man is 888 (by an ex-emperor of Morocco); that by a woman, sixty-nine (over twenty-seven pregnancies). And even at a more mundane level it is much easier for a man, potentially, to have more children than a woman – for the obvious reason that whereas a man can have his children with several different women, a woman (until the recent advent of surrogate motherhood) has had to have all her children herself. A successful son, therefore, can give a woman far more grandchildren than can a successful daughter. The higher a son’s eventual social status, the more successful he is likely to be. Since wealth and status, as well as the genetic potential to achieve wealth and status, can be inherited, we might expect higher-status couples to produce more sons than lower-status couples – and they do. Studies around the world have shown a male-biased sex ratio among the children of couples of higher status (take, as an example, the children of the men and women listed in the national Who’s Who). Usually the bias is statistical rather than obvious – about 115 boys for every 100 girls – but sometimes it can be impressive. The presidents of the United States, for example, have between them produced ninety sons and sixty-one daughters, the equivalent of 148 sons for every 100 daughters.
So why don’t all women produce an excess of sons? Actually, to some extent they do. On average, about 106 boys are born for every 100 girls. But because boys are more likely to die during childhood, by the time the survivors start to reproduce the proportion is about equal. Even so, not only is the average woman less likely to have a boy than a woman paired to a high-status male, but women paired to low-status males and women without a partner at all are more likely to produce a daughter. Why?
The answer is that a son is a much more precarious reproductive option than a daughter. Despite his potential to produce large numbers, he is more likely to die before he begins to reproduce, and he has much more chance of not reproducing at all, even when he tries. If they are not reproductively competitive, sons are a poor option. Imagine a society in which all women produce only two children: for every man who sires six children with three different women, there will be two who fail to sire any. There are two ways in which a daughter is the safer option: first, although relatively few daughters produce large numbers of grandchildren for their mothers, relatively few fail to produce any; second, a mother can be certain that all of the grandchildren produced through a daughter are hers. She cannot be so certain about the grandchildren apparently produced by a son.
Thus, only when there is a very good chance that a son will not only survive but will also be reproductively competitive against other males is it worth producing a boy. So, in principle, we should not be surprised to find that women without long-term partners and women paired to lower-status males produce an excess of daughters – or to find that those paired to higher-status males produce an excess of sons. Nor should we be surprised that, in between these two extremes, most women compromise and show no bias towards either sex.
The woman in Scene 18 got it exactly right when she produced a daughter from her ‘accident’ while she was still at school, and two sons when she was paired to a wealthy man of high status. Just how she will have achieved this bias is not known. The explanation is not that higher-status males produce an excess of ‘male’ sperm – the casual lovers of such men produce an excess of daughters, as they should. Nor does it seem likely that high-status males introduce an excess of ‘male’ sperm into their partners but an excess of ‘female’ sperm into their lovers. The only reasonable explanation is that the bias is generated by the woman. Either her body biases the proportion of male and female sperm allowed through to the fertilisation zone in her oviducts, or she is selective about which embryos she allows to implant following fertilisation. Maybe, if the embryo is the ‘wrong’ sex for her circumstances, her womb does not let it implant (Scene 16).
To most people, the whole process of mate selection is a minefield of distractions and pitfalls, particularly during late adolescence as a boy or girl searches for their first long-term partner. The woman in our scene subconsciously wove her way through this minefield with precision. She did so by virtue of the excellent genes she herself had received from her parents. As a result, she ended up with three children, and perhaps eventually more, all sired by a man or men who were reproductively outstanding in their peer group. Her daughter had already begun to produce grandchildren; her sons had great potential, not only to produce their own families but also to be the targets of other women’s infidelities. She had every indication that her descendants would multiply and flourish. In later generations, her genes would mark more of the population than would the genes of her less successful contemporaries. Her life had been a success – both biologically and hedonistically.
SCENE 19
Fair Exchange
It was Saturday night and the two couples were sitting cross-legged in a circle on the floor. With plenty to drink by their sides, they began to play cards. Each of them was privately tingling with nervous and sexual excitement. They had great hopes that the next hour would be a sexual landmark in all of their lives.
They had known each other for seven years. Although they had always found each other’s partner sexually attractive, no infidelity had ever occurred. The first couple, despite five years of unprotected sex, had no children. The second couple had two. In recent years, for different reasons, each couple’s relationship had been foundering.
The childless couple felt an undeniable emptiness in their lives, which they could not shake off despite all their money and travelling. When they first met, they had seemed perfect for each other. He was tall, muscular, ambitious, witty and dominating. She was effervescent, open and liberated, always dressing provocatively. Women surrounded him wherever he went and he could have had a new sex partner every week if he had wished – and he did . . . often. She, also, was much sought after. Once regarded as an item, they gained great kudos from being each other’s partner and, despite their earlier promisc
uities, had settled into a serious relationship.
Four years later, after a year of unprotected sex, they had been screened for infertility but there was no clear indication that either was infertile. She was ovulating, had no blocked tubes and seemed normal. He was producing rather large numbers of sperm, but otherwise also seemed normal.
At first, they responded to their problem with intense sexual activity, but after a further year of failure they gradually lost interest in routine sex. Secretly, they both hoped their combined failure was the other’s fault, and this thought had led them to be critical of each other’s sexuality. She now saw his size and power as futile, boorish and selfish. He now saw her free conversation and provocative dress sense as public vulgarity, a front to hide her private frigidity.
The couple with children were very different. Both were attractive in their own way, but were much less extrovert than their friends. What little social kudos they had came from their association with the childless couple. The man was small, quiet, hard-working and reliable. The woman was demure, sympathetic and maternal. It had taken them eight months of effort to conceive each of their two children but eventually it had happened and, as a parental team, they were wonderful. When he was not working they were hardly ever out of each other’s company.
Lately, however, increasing financial hardship had produced friction between them. Their situation had been aggravated when his employers, dismayed by his lack of ambition and charisma, moved him sideways to a lower-profile position. Now, increasingly frustrated by her partner’s mundane job, she was often critical of his inability to improve their situation. For his part, having pushed his partner into full-time motherhood, he now found her demure quietness dull and unattractive.
Recently, each couple had sought to bolster their flagging sexual interest with pornography. But over the weeks the impact of the images had worn off. Then, when the four of them started to watch films together, excitement had been briefly rekindled. Even that source of excitement, though, had eventually begun to wane - until tonight. The idea for the ‘game’ they were about to play had been seeded by a film showing partner-swapping. In the video they had just watched, the men had thrown their car keys into a pile in the centre of the room. The women chose a key, then paired off with the owner. Soon the room was full of naked, copulating bodies.
