The mode of passion is born of unlimited desires and longings … and because of this one is bound to material fruitive activities.
Baghavad-Gita
‘I’d much rather have bigger breasts than smaller breasts. I like the power of the female form over men, and using it to get what I want.’
Anonymous interviewee ‘A’
A few minutes spent at a newsstand provides evidence enough that women and men have different ideas of what makes female bodies beautiful. Women’s magazines usually have women on their covers; men’s magazines often do too, but those women do not look the same. Their bodies differ, often their faces and expressions differ, and their poses differ.
For now I will put aside the thorny question of why heterosexual women might want pictures of other women on the covers of their reading material – we will come back to this later – but it seems obvious why heterosexual men do. Yet what still requires explanation is why, exactly, men are so visually fixated on the female form, and how they acquire their particular visual preferences. Men like looking at beautiful female bodies, and studies show that men are especially keen to date women whose bodies have already been endorsed as attractive by other men. In more scientific terms: visual assessment is a major determinant of the initial stages of mate choice by male humans.
So why is the look of the female body so important? The male quest for female beauty is so deep-seated that it must indicate something more than just the pathological superficiality so often ascribed to men. And indeed, everywhere else in the animal kingdom we find individual creatures behaving the same way – lured by the shallow visual advertisements of the opposite sex. Thus human men are certainly not unique in seeking visual evidence that potential lovers may be ‘the one’, or at least ‘a one’ – a future partner with whom they can most confidently pass on their genes.
Yet surely beauty is, at best, only an indirect indicator of how good a co-parent someone will make? Indeed, in the modern developed world the evidence is patchy. Some studies suggest that beautiful people are no more likely to have children or be healthier than less beautiful people, whereas others claim that individual components of beauty are very strongly linked to genetic health and vigour. In particular, there is evidence that more attractive people are cleverer – up to twelve IQ points cleverer in some studies – than less attractive people. Maybe the man at the bar who looks you up and down really is only interested in your mind.
In this chapter I will examine what attracts heterosexual men to women’s bodies, and why. I appreciate that, after three chapters looking at the grand forces which have forged the female body we see today, you may consider this a rather tawdry way to start investigating the immense power which the female body exerts over the humming loom of the human mind. However, male desire is important because it has been a potent force in the evolution of women’s bodies, and today that desire still holds almost half of the human population in its thrall.
Some of us may not look like it, but each human alive today is the product of thousands of generations of heterosexual lust. We are here because again and again, nameless men and women liked the look of each other, and liked it enough to want to have sex. Simply surviving and being successful was not, in itself, sufficient. To contribute to the gene pool of future generations, each of our ancestors also had to find someone to make babies with. Being alive was not enough – ancient humans had to be wanted too.
Charles Darwin realised that this was a big problem with his theory of evolution by natural selection. Everywhere in nature there are animals which have survived and prospered, yet are never selected as anyone’s mate – many deer stags, for example, make it to a healthy adulthood, yet never sire a calf. Indeed, it is now clear that natural selection has a racier counterpart to account for this – sexual selection. Sexual selection means that animals produce lots of successful offspring not only because they are able to survive, but also because they possess traits which make them more likely to acquire sexual partners. These traits might allow them to compete with members of their own sex – as in the evolution of the human fist I mentioned in Chapter 1 – or they might make them more likely to be selected as mates because they are, well, more attractive.
One important implication of sexual selection is that species may acquire many of their distinguishing features because they are attractive to the opposite sex, rather than because they are of any practical use. For a characteristic to be sexually selected it must presumably exist in a rudimentary form in the first place, and then be interpreted as a sign of vigour by the opposite sex. The peacock’s tail is biologists’ favourite example of this, but what if the same were true, for example, of women’s buttocks? If sexually selected traits are practically useful too, then all is well, but even if they are not useful they can still win out – at least until the moderating hand of natural selection eventually intervenes and eradicates the peacocks with the most ridiculously extravagant tails, or the women with the most cumbersome bottoms.
Of course, sexual desire takes two, and this is why sexual selection can be such a powerful thing. If, for example, feminine buttocks really are an indicator of health and fitness, then men who like them will end up siring offspring with a better chance of survival. Thus the genes for ‘buttock-liking’ (which unfortunately have not yet been identified) would themselves confer a beneficial trait which is propagated in future generations, along with the ‘counterpart’ genes for curvy buttocks. Rather pleasingly, what results is not a genetic arms race, but a genetic love-in – as genes which cause attractive characteristics, and genes which instil a desire for those characteristics, spread and become more potent. Women’s buttocks swell; men like them; everyone is happy.
This may sound simplistic, and not very politically correct, but the scientific evidence for sexual selection is extremely strong. Despite the fact that it can be difficult to tell which characteristics evolved by natural selection and which by sexual selection, it is very likely that elements of human female body shape evolved as a result of the latter. This is why human males’ desire is so important if we want to truly understand human females’ shape.
Before we look at what specific things men find attractive about women, there are two aspects of sexual selection which deserve mention. The first of these is that the sex which contributes most to childcare gets to sexually select the other sex. Peahens lay eggs and look after peachicks, while peacocks prance around being generally unhelpful. This may seem unfair, but it does mean that peahens hold all the cards, as it were – they put in most of the effort, so they can be as dowdy as they like yet still get to select the sexiest peacock. By contrast, everything is much more egalitarian in humans. As we have seen previously, humans are unusual among mammals because paternal investment is extremely important for the success of our offspring, and because of this human males are unusually choosy about their mates. Most male animals will mate with anything that looks vaguely female because copulation will be the end of their contribution to the next generation, whereas human males have to be careful about the individual with whom they are going to co-parent for the next few years, or even decades. As a result, unlike most female mammals, female humans are subject to powerful sexual selection – just like men. They get all that help with the kids, and they get desired too.
A second feature of sexual selection is also especially relevant to the human female body. You might expect that a few thousand years of sexual selection by men would result in every woman having a body like Beyoncé or Bardot – yet this does not seem to have happened. In fact, far from making the ‘desired’ sex all tend towards one single ideal, sexually selected traits often exhibit much more variation than naturally selected ones. There is probably only one good way to make a woman’s spleen, and this is why they all look rather similar – whereas if breasts, buttocks and waists are indeed sexually selected traits, then this could explain why those things vary so much. In previous chapters, I did not come up with many convincing explanations for the extreme variability we see every day in women’s body shapes, but sexual selection might now explain that variation for us. Perhaps men have spent the last few hundred thousand years sexually selecting mates for all sorts of different reasons, or maybe they are just inherently catholic in their tastes.
Hopefully a detailed examination of male sexual desire will help us discover whether it really is men who have made women such a beautiful and diverse bunch.
Reproductive theorists enjoy making generalisations. They believe that all animals – including humans – have similar aims when choosing mates. The drive to propagate one’s genes in successful offspring constrains us all into a remarkably restricted array of likes and dislikes when it comes to the opposite sex. These biologically determined desires make us uncomfortable when they are applied to humans, but they persist nonetheless. For obvious reasons, in this chapter I will focus on the things that heterosexual men look for in women (and especially their bodies), but many of these general principles apply to heterosexual women’s desires too.
The ‘big three’ desirable features for a heterosexual man’s mate are perhaps unsurprising – femininity, health, fertility. Men seek women who look obviously like women; men seek women who have good genes and are healthy; men seek women who look like they have years of efficient breeding ahead of them. Of course, these three desires may overlap in complex ways, but they all make sense to a male keen to pour lots of his genes into the next generation.
The ‘additional two’ lusted-after traits – genetic difference and similarity – are more confusing, because they are opposites. Of the two, genetic difference is the most straightforward: it seems sensible for men to want to breed with women who are genetically dissimilar to themselves, to avoid inbreeding. This is a pressing problem because we all carry damaged genes – every one of us may inherit from each of our parents roughly ten mutations which could potentially cause lethal genetic diseases – but luckily most of us also inherit a ‘good’ copy of each of those genes from the other parent. However, if men mate with closely related women, their children are far more likely to end up with two copies of one of those damaged genes, often with disastrous consequences. Desiring genetic difference safeguards against the calamity of inbreeding.
Despite this, seeking mates who share characteristics, and thus presumably genes, might also promote the future survival of men’s own genes, especially if those genes are particularly good at promoting survival in the local environment. Indeed, there is good evidence that heterosexual humans achieve this genetic-similarity-seeking by ‘imprinting’ on their ‘other-sex’ parent as a model of desirability. For example, studies show that adopted children end up preferring mates who look like their adoptive other-sex parent rather than their biological other-sex parent. This may make for disquieting reading – no one likes to see the words ‘parents’ and ‘mates’ in the same sentence – but the fact remains that humans seek a delicate balance between genetic similarity and difference in their sexual partners.
Intelligence
But enough of generalisations about male desire. What exactly do men look for in a woman?
For the purposes of answering this question, it is fortunate that the inherent sexism of science means that there has been more research into what men find attractive about women than vice versa. And these studies show that there is a central biological core of non-negotiable heterosexual male lust. This core can be modified and supplemented by cultural influences, but it remains stubbornly present. For the rest of this chapter, this is all going to be very universal and very primal.
In fact, there is only one thing that a man looks for in a woman that is not related to body shape – intelligence. Many researchers claim that this has been scientifically neglected at the expense of studying more ‘superficial’ characteristics, but I suspect this is simply because men’s reactions to intelligence and charm are harder to measure than attraction to physical attributes. Anyway, it makes sense for men to find intelligence attractive, as intelligent women are likely to make more sensible decisions about caring for their children in the future. Intelligence is also a characteristic which implies that a woman has herself received good care and abundant resources from her parents, and has thus hopefully inherited good parenting skills. In addition, studies show that intelligence correlates well with general health. Indeed, some have claimed that art, music and humour evolved expressly so that humans could demonstrate their intelligence, and therefore their implied vivacity, to the opposite sex – which may explain why pop stars receive so much sexual attention.
In addition, men certainly find some behaviours attractive in potential mates, but these are even harder to quantify than intelligence. Various studies suggest that men actively seek signs of emotional stability, nurturance, dependability, sexual fidelity, and probably some similarity with themselves in personality traits. They also look for evidence that women are interested in them – playfulness, for example, seems to be identified as a sign of both youth and sexual engagement. Women’s smiles activate men’s orbitofrontal cortex, in the same way that many aspects of visual attractiveness do, so men probably do think women are prettier when they smile. And of course, women’s voices are attractive to men too – their higher pitch is a badge of femininity indicative of a small larynx, resulting from low androgen concentrations at puberty. Studies even show that men find women’s voices more attractive around the time of ovulation, when oestrogen levels and fertility are at their peak.
Aroma
The second set of features which men find attractive is, perhaps strangely, related to smell. There is a great deal of research which shows that many animals – rodents, fish and birds, for example – select their mates largely on the basis of their odour. In these species, individuals secrete odorants (smelly chemicals) which vary according to the presence of certain genes important in the immune system. A female mouse, for instance, deliberately selects mates that smell like they have different immune genes to her, so that her offspring will inherit a varied mix of genes from their two parents. In other words, seeking a genetically dissimilar mate can make your children more able to fight disease. And remarkably, experiments with pre-worn T-shirts suggest that women do precisely the same thing, and seek out immune-different men. Research even suggests that women married to immune-similar men are more likely to be dissatisfied with their relationship and have affairs.
The evidence that men use smell to choose their mates is less clear-cut, probably because these visually obsessed creatures tend to see women before they smell them. However, odours can affect many different areas of the human brain, and it is likely that men subconsciously find women’s smells attractive in a variety of ways. A small amount of evidence suggests that they too may select partners on the basis of immune-difference, and that they are well able to discern genetic similarity and difference in general. For example, human subjects can often identify their other-sex siblings by smell, and they can sometimes identify their same-sex siblings too; they are less able to detect the smell of half-siblings, and even worse at detecting their step-siblings.
There are also intriguing indications that men can smell the hormonal basis of femininity itself. Oestrogen-like odorants activate men’s hypothalamus, an area on the underside of the brain involved in sexual behaviour, and smelling these odorants even makes men think women’s faces look more feminine. Indeed, smell may be strongly linked to vision in complex ways – for example, women with symmetrical faces are more likely to be rated as pleasant-smelling by panels of blindfolded men, especially around the time of ovulation.
Youth
The third element of female attractiveness is the one that causes the most argument: youth. Evolutionary theory dictates that men should seek women with the greatest future reproductive potential – because a man who hooks up with a young woman can exploit many years of future baby production. These women should also be obviously fertile, however, and this is why studies show that most men find women in their early twenties more attractive than teenagers. Yet these are not simple urges, as analyses of lonely hearts ads show that men in their late teens prefer women slightly older than themselves, and that this preference wanes until, at roughly twenty-three, they desire women who are similar in age. From then on, the preferred age gap steadily increases in the other direction until men in their seventies seek female partners ten or fifteen years younger than themselves.
This much maligned male quest for youth actually has rather comforting origins. In contrast to most other male mammals, human males seek long-term pair-bonds with females, probably because human children need bi-parental support for extended periods of time. Thus it makes sense for a man to find a woman who is at the start of her child-supporting phase, because he intends to stick around. By contrast, chimps breed promiscuously and do not pair-bond, so males show a preference for older females because they are more experienced at caring for the babies with which these simian lotharios impregnate them.
Some may find it hard to accept that men’s attraction to younger women is a reflection of their compulsion to relationship fidelity, but the evidence is all around us. In all human cultures, heterosexual men are, on average, older than their partners. Indeed, male homosexuals seek younger partners too, so this seems to be a general feature of the male brain. A Swedish study showed that women whose partners are four years older than them produce more children than women whose partners are closer to them in age, and a US study showed that teenage girls are less likely to use contraception or have abortions if their partner is more than six years older than them. Clearly, these preferences are built into all of us.
Some of the cues men use to detect women’s age may be behavioural or intellectual (or they may simply ask them), but visual attributes are probably more important. Research shows that skin smoothness is a strong cue of youth, as are thick, non-greying hair and healthy teeth. And as far as the body is concerned, men are adept at noticing the age-dependent changes in breast shape, waist size and the evenness of skin tone and texture I discussed in Chapter 2 – however, in all these respects, different women may appear to ‘age’ at different rates. Yet for the average instinct-driven man this variability simply may not matter. After all, reproductive theory suggests he may not be as interested in absolute chronological age as he is in future reproductive vigour. We might also expect human males to naturally adapt their age preferences to their partner’s advancing years, to encourage them to maintain the pair-bond and complete their investment in their children.
Face
With the fourth set of characteristics men use to determine attractiveness, we come to something which overlaps even more with body shape – facial beauty. Contrary to what women might think, men do spend a lot of time looking at their faces, and recent advances in computing have made this a rich area of research. Artificially constructed facial images can now be tweaked and distorted prior to being shown to men and asking how attractive they find them – and this has at last allowed us to dissect the elements of female facial beauty.
For example, facial symmetry is, in itself, attractive. While slight asymmetries seem to be acceptable, the evidence is clear that faces computer-morphed for symmetry are considered more beautiful. If a woman’s face and body are extremely symmetrical, then this suggests that flawless genetic and developmental processes moulded her, so it is only natural for men to want to get some of that flawlessness incorporated into their future children.
In fact, the ‘genetic stability’ implied by symmetry goes further than that, as studies indicate that symmetrical people are healthier throughout life, are more intelligent, suffer fewer psychiatric disorders and even have more attractive voices. The human brain is extremely good at detecting asymmetry, especially in faces. But symmetry comes with a catch: it can make faces seem unemotional or even boring. This may be why women often choose to have extremely asymmetrical hairstyles, or even beauty spots, to contrast their attractive symmetry with a lopsided artifice of quirkiness and vivacity. I also suspect that eye symmetry is especially important for beauty – after all, we all spend a lot of time gazing into each other’s eyes, and constructing something as wonderful as a pair of human eyes requires a bewilderingly choreographed intermeshing of developmental processes. So when a man says a woman has beautiful eyes, he is probably not saying it just because he cannot think of anything else to say.
It has been suspected for some time that ‘averageness’ is another component of female facial beauty – having all facial proportions and features of a moderate size, with none exceptionally large or small. While one can easily think of beautiful women with larger noses or smaller chins, for example, computer modelling studies suggest that the desire for averageness is a very real phenomenon. When presented with images of real female faces as well as composite faces computer-blended from several images of those same women, men usually prefer the composites, the ‘averaged-out’ faces. This may seem like a tendency to prefer blandness, but some researchers believe that it is as important, if not more important, than symmetry. Of course, in real life the two things overlap – an average face is, by its nature, fairly symmetrical, and symmetrical faces represent the average between wonky extremes.
A lesser contributor to facial beauty is that men prefer women whose features share some similarity with their own – and I mentioned previously that this may be caused by ‘imprinting’ on their own mothers during their boyhood. We may worry about men who date women who look like themselves, and even more about those who date women who look like their mothers, but once again computer studies confirm that this disquieting desire for similarity does indeed exist. If elements of a man’s own face are blended into an artificially constructed female visage, then he will tend to find it more attractive. This may be a weak effect, but nonetheless it is an example of men seeking similarity – in contrast to the odour data which suggested that they seek difference.
Facial femininity is an extremely important contributor to men’s assessments of beauty: they want women to look like women. In previous chapters I described how the dramatic physical differences between women and men evolved – how sexually dimorphic our species has become. And today, men’s desire for overtly feminine women may result from aeons of sexual selection making women look womanly and, as a consequence, men have accumulated genes which make them desire that womanliness. However, being attracted to obvious femaleness may also have other advantages – it allows men to direct their sexual interest towards mature women, and especially women who are vigorous enough to maintain the luxury of these ‘non-essential’ traits. In addition, there is evidence that women with exaggerated female traits develop sexually at a younger age, so that men who select very feminine women may be able to benefit from their unusually extended child-producing life.
There are many characteristics which men’s brains identify as feminine, but they fall into three main groups. The first group includes features which women retain from childhood but men do not – such as having a small nose, a small chin, large eyes, thin eyebrows and prominent lips. The second group consists of characteristics which are driven by female sex hormones – including rosy lips and cheeks (although these may also indicate sexual arousal). The third group includes features which result from a lack of male sex hormones – an oval, upward facing, ‘open’ facial morphology with large forehead and small jaw, and also pale skin. Androgens tend to make facial skin darker, so men prefer women with pale facial skin which contrasts strongly with their features.
Apart from symmetry, averageness, similarity and femininity, we are left with one more, rather rag-bag set of facial characteristics which men find attractive, and each of which, we suspect, sends men a specific signal. For example, men find women with dilated pupils more beautiful, probably because it suggests sexual arousal, and this is why women, from the time of the Babylonian Empire to mid-nineteenth-century Paris, used to artificially dilate their pupils with the poison atropine (belladonna – Italian for ‘beautiful lady’). Also, unlike skin smoothness, which men use as an indicator of youth, studies show that even skin tone – something explicitly promised by the manufacturers of cosmetic foundations – is used by men as an indicator of not just youth, but health too. In past times when viral and bacterial skin diseases were commonplace, this may have been of even greater importance. It is no coincidence that in medieval England, milkmaids, who tended to have acquired immunity to smallpox due to transient minor infections with cowpox, were often called ‘pretty maids’.
Lower curves
By the time we reach the fifth and most important component of male desire – lower body shape – it is already clear that heterosexual men come pre-installed with a powerful set of drives to help them select healthy, fertile, feminine mates. However, it is in their inquisition of the female body that men demonstrate their greatest deductive powers. In recent years there has been a flurry of research into this area, to the point where individual genes related to assessing attractiveness have been identified, as have specific regions of the male brain which respond to, for example, images of nude female bodies.
Some researchers claim that the most important criterion of female body shape is body mass index, which is a reasonably good indicator of fatness. We think fatness is important to men for several interlinked reasons. First, subcutaneous fat is a sign of femininity because, as we have seen, human females deposit large adipose stores to meet the demands of gestating and rearing children – especially their children’s large and lipid-rich brains. This is why human female fertility turned out to be so dependent on the flows of fatty calories through the body. So a man who seeks a fat-laden lady may simply be seeking a feminine, fertile partner who is well provisioned for future baby-making. However, being well provisioned says even more about a woman than that – it also implies that she is intellectually or metabolically able to acquire and store valuable calories, or that her parents did a good job of acquiring those calories for her. Either way, she is evidently full of energy – literally – and probably full of good genes and sense too. And indeed, some brain scan studies suggest that body mass index is indeed the best way to stimulate the appropriate parts of the male brain.
There are, however, problems with the idea that body mass index is the main thing men look for. First of all, how is your average chap meant to calculate this esoteric ratio? It may be clinically useful, but I doubt that the male human brain can measure it directly. Some have suggested instead that men are more swayed by women’s percentage of body fat, but that seems like an even more difficult thing to measure at a glance. Moreover, men do not simply like women with high body mass indices, but rather they prefer women with moderate indices – in the same way they like ‘average’ faces. At present, Western men prefer women with near-average or just-below-average body mass indices, but that tells us little because averages change over time. As we will see in a later chapter, women’s average body mass indices have changed over the course of history and also vary dramatically around the world today – and men’s preferences for fatness have been similarly inconsistent.
A second measure of body shape seems more convincing as a trigger of male desire, although it too is imperfect. This is the waist–hip ratio I mentioned in the last chapter – the circumference of the waist divided by the circumference of the hips. I realise that ancient male hunter-gatherers did not possess tape measures, but the ratio can be estimated by dividing the waist width by the hip width too, which is something I can imagine the male human brain could easily achieve. Wide hips and narrow waists are easy to see. This measure of curvaceousness has the advantage of indicating shape, not absolute size; it is independent of height, and as a result it may reflect a woman’s underlying metabolism and hormones rather than how much food she happens to have eaten recently.
Until puberty, the waist–hip ratios of girls and boys are similar, but once sex hormones take effect women’s hips outgrow their waists dramatically so that a woman’s ratio is usually less than 0.80 whereas a man’s is usually more than 0.85. Many teenagers wear low-cut trousers nowadays, but only teenage boys like them to look like they are falling down, demonstrating how masculine and hip-less they are. Conversely, men like women to have low waist–hip ratios because they indicate a combination of femininity and sexual maturity, as they result from high levels of female hormones at puberty. This form of curviness also represents a desirable pattern of fat deposition to men because it signifies that women can establish discrete adipose stores to support reproduction, without laying down general fatness for their own use. Throughout the tough years of our species’ evolution, men wanted well-provisioned children more than they wanted rotund partners.
The desire for low waist–hip ratios may also be linked to pregnancy, but in a double-edged way. We have seen that women’s hips originally became wider to increase the size of the birth canal for our brainy babies to pass through. They then augmented this wider silhouette with external fat, partly because it is a valuable calorie store but probably also because men had come to associate hips with femininity. However, it has been claimed that hip fat has become ‘false advertising’ of the size of the pelvis beneath. Indeed, the fact that women with broad hips may still experience birthing problems suggests that men can to some extent be ‘fooled’ by curvy hips.
Conversely, some researchers claim that men’s obsession with waist–hip ratios actually stems from a desire to avoid futile dalliances with women who are already pregnant, because waists get wider during pregnancy. I am not convinced by this argument for two reasons. First, we should expect men to be attracted to pregnant women so that they maintain the pair-bond throughout their female partner’s pregnancies – and indeed they often are. And second, the bulge of pregnancy is a very different shape from that of obesity, or the wide-waistedness of maleness. Indeed, many women’s bellies ‘bulge forward’ during pregnancy, so that their waist–hip ratio is still readily evident from behind – incidentally a sexual position often preferred by expectant couples.
The evidence for the importance of waist–hip ratio is quite good. Many studies show that men prefer narrow waists contrasting with wide hips – the consensus ideal ratio may lie somewhere around 0.70. Although later I will discuss the possibility that there is ethnic variation in this optimum, the general male preference for a low waist–hip ratio has been demonstrated in disparate cultures around the world and brain scan data also show how low ratios fire up areas of the male brain associated with attraction. And as if to validate men’s predilections, some studies suggest that women with low ratios do indeed experience fewer problems during birth, bear more children, suffer less chronic disease and may even be more intelligent. These data are hotly contested, but it must be admitted that the waist–hip ratio also does what one would expect it to do as women get older: as the power of sexual selection wanes with age, so the waist–hip ratio rises, a change disliked by many middle-aged women because they see it as de-feminizing.
Breasts
If, to men, curviness indicates maturity, femininity, provisioning and a woman’s ability to focus resources on offspring rather than herself, then of course breasts must also be important.
There are various measures of breast-curviness, but waist–bust ratio seems as good as any, and once again men prefer low ratios – slim waists and relatively large breasts. Here too, some studies suggest that this male preference is universal across human cultures, although others have disputed this. Certainly, eye-tracking studies, in which men’s gaze is electronically recorded as they look at women, suggest that waist–bust ratio is important – when men first view a woman’s body, they look most at the breasts and the waist, and less at the hips, genital area or legs (I will discuss my theory about legs in Chapter 9).
In fact, breasts have generated the single most longstanding and polarised argument about the role of men’s desire in the evolution of women’s bodies. Uniquely among animals, human females’ mammary glands are often large and pendulous when they are neither pregnant nor breastfeeding – or if not large, they are usually an appreciable fraction of their full ‘lactation size’. To evolutionary biologists, this uniquely human characteristic really does demand explanation, because possessing such large non-lactating breasts is zoologically bizarre. We have already seen that breasts can severely limit women’s movement – most would find it painful to run for any length of time without physical support – and large breasts can also cause back pain. There must be something which balances out these disadvantages of large breasts, but what is it?
One group of researchers maintains that humans evolved always-pendulous breasts because they actually serve a useful function – in other words, they were naturally selected over the course of human history because they increased women’s chances of rearing their offspring successfully. One suggestion is that the modifications to the shape of the human head – the dramatic reduction in jaw size and the flattening of the face – meant that human infants had trouble breathing during suckling. And so, instead of the infant muzzle protruding towards a flat breast, a protuberant breast grew out to engage with the flat infant face. This is a reasonable idea, but there are other relatively flat-faced primates in existence, such as gibbons and marmosets, and their females do not have permanently swollen mammary glands. And women with very small breasts do not seem to have undue trouble with the mechanics of breastfeeding.
Another functional explanation relates to the fact that human infants are often carried in their mothers’ arms or perched on their hips – something uncommon even among primates. Unlike other mammalian infants who cling to their mother, or who follow her around on four legs, human infants may not always find it easy to reach the breast, so maybe the human breast evolved to dangle bralessly down towards babies’ mouths and be grasped by their hands. An extension of this theory comes from those who claim that humans went through a semi-aquatic phase during their evolution, and that prominent breasts were a convenient handhold for infants to seize as they bobbed about in the water. However, any theory that involves active grabbing of lactating breasts seems unlikely to me, as breastfeeding women find this sort of thing extremely uncomfortable.
The evidence for these functional explanations of human breast morphology does not seem convincing to me. Breasts are mechanically very weak, comprised mainly of soft fat with a flimsy connective tissue capsule which gradually deteriorates under the force of gravity. They are hardly structures suited to a mechanical function. Besides, to reach down to and slot into a distant flat-faced infant’s mouth, breasts could just as well be long and thin, not globular, and would then impede women’s athleticism less. Finally, the function-based theories cannot explain why the breasts swell early on during puberty, before girls can actually become pregnant, and long before they usually do.
An opposing group of researchers claims that, whatever function female breast enlargement once had, most of the pendulousness is the result of sexual selection by men. And indeed, it seems clear why men should desire large breasts, even if this conflicts with their potential mate’s ability to run around. Breasts are visible stores of fatty calories in their own right, and they also represent an important component of women’s general curviness. They are particularly large during pregnancy and lactation – times when women cannot conceive, but when it is crucial for men to maintain their enthusiasm for the pair-bond. Some studies even suggest that breasts swell and become more attractive around ovulation, as a direct lure for human males. Indeed, breast size may directly stimulate provisioning by the male brain – and studies show that men are more likely to take a large-breasted woman out to dinner on their first date. One theory, perhaps unlikely, even suggests that human breasts evolved to maintain men’s copulatory interest by mimicking the buttocks they had been so used to ogling before human coitus switched to being a more face-to-face activity.
If always-pendulous human breasts are indeed a sexually selected characteristic, then they probably send mixed messages about age. We have already seen that men tend to seek relatively youthful partners, yet young women tend to have smaller, and certainly less pendulous, breasts. Also, women with smaller breasts are likely to be pleasantly surprised in middle age when their breast shape remains more youthful than their more buxom friends. So as women get older, men potentially face a sexual dilemma between choosing partners with large breasts or with youthful-looking breasts.
Despite the complications related to age, there is strong circumstantial evidence that breast shape is a sexually selected trait. For example, enlarged breasts are permanent features after puberty, they are sexually sensitive only in humans, they are attractive to males only in humans, and their size correlates poorly with their biological function of producing milk. Moreover, breast size is extremely variable between women, and variability is also often a product of sexual selection – some women have breasts ten times larger than others, but the same is not true of eyeballs, thighbones or other functionally selected bits and anatomy. Human breasts even have an additional tell-tale visual advertisement for men – the areola, the pigmented region of skin around the nipple. The areola is a distinctive human innovation, and studies show that it particularly attracts men’s gaze, and that they find it especially attractive if it contrasts strongly with the surrounding skin.
So if most of the evidence suggests that human breasts are primarily products of sexual, not natural, selection, women can thank or curse generations of breast-obsessed men, and the generations of women who loved them, for their current shape.
And as it happens, men may derive some surprisingly detailed information from breasts, which could explain why they like looking at them so much – analysing them, almost. Symmetry seems to be even more important for breasts than it is for faces. Yes, many men like large breasts, but they like symmetrical breasts more – and small breasts are more likely to be symmetrical than large ones. We assume that breast symmetry indicates genetic health and developmental ‘stability’, and indeed it does predict future fertility, it reflects high oestrogen levels, and it can be inherited in the form of symmetrically breasted female offspring. There are also suggestions that women with symmetrical breasts are more intelligent. So heterosexual men’s apparent obsession with breasts may actually reflect a benevolent wish to optimise his future children’s intellect.
While some of these ratios, symmetries and pendulosities may seem abstract, it is clear that even if men do not measure them directly, the womanly curvaceousness these features represent certainly attracts them. The power of curves over men – and their implicit guarantee of maturity, femininity, health and fertility – is clear. As for specific numbers, here are the ratios which one study suggested are preferred by the two sexes when assessing women’s bodies:
| body mass index | waist–hip ratio | waist–bust ratio | |
| men’s preference | 18.8 | 0.73 | 0.69 |
| women’s preference | 18.9 | 0.70 | 0.67 |
It is obvious that the men in the study liked moderately slim women with narrow waists, broad hips and large breasts, but even more noticeable is how similar women’s female body ideals were to men’s. Indeed, the women preferred slightly more busty and wasp-waisted women than the men did, and certainly a more curvaceous shape than the female participants themselves possessed, so it seems that men are not the only ones imposing expectations of curviness on women.
However, although the sway which the curvaceous female form holds over men’s sexual desire seems to have been established, there is one issue which few of the studies have addressed directly. Science tends to focus on averages – the average waist–hip ratio desired by men, for example – but what of variety? Of course, heterosexual men vary in their body-tastes, and this ‘between-man’ variation can be measured. For example, the recent omnipresence of internet technology means that men who desire female bodies at the extremes of the spectrum can now form what are rather charmingly described as online ‘communities’, through which they can validate their own preferences for large, small, muscular or pregnant women in the comradeship of other men with similar penchants (and swap pictures, of course) – and also unwittingly constitute an enticing resource for researchers. Individual men’s preferences also change according to their experiences – for example, studies show that stressed men prefer women with higher body mass indices, and long-term relationships tend to lead men to develop over-optimistic ideas of their partners’ objective attractiveness.
Beyond this between-male variation, there is an even more important, but less easily studied effect. Put simply, individual men do not blindly seek only women who accord precisely with their own preferred ideal physique. Most men find a wide range of female body shapes attractive, so long as they look obviously female, and also somehow ‘right’ for each individual woman. Maybe this male acceptance of female variability is why ratios matter more to them than absolute measurements. Thus there is also ‘within-man’ variation, which I like to call ‘body-flexibility’. And I believe that men are more body-flexible than many people realise, and often more body-flexible than women.
Women pictured in men’s magazines, for example, often reflect a wider range of body shapes than those in women’s magazines, and certainly a wider range than is seen in fashion models. For example, studies show that even Playboy playmates vary in shape, are not unusually slim and are not becoming progressively slimmer over the years, although they do often have more curvaceous ratios than the average woman. The movie and pop stars who are most lusted-after by men – the real icons – are again a varied bunch: Marilyn Monroe, Jayne Mansfield, Audrey Hepburn, Brigitte Bardot, Debbie Harry, Angelina Jolie, Gwyneth Paltrow, Beyoncé Knowles. Fashion models, in contrast, are generally thinner, less variable and less curvaceous than most women, and often have waist–hip ratios higher than the average teenage boy – but they work in an industry in which heterosexual men may wield less influence than elsewhere.
Thus women may have men to thank not only for their distinctive body shape, but also for the dramatic variation in that body shape. And biologically, body-flexibility makes a lot of sense for heterosexual men. They should seek partners who are obviously female, mature, healthy and fertile, but they must not be so blinded by absolute size that they ignore brains, faces, smells, and of course mutual attraction. And once they have found their partner, it makes even more sense for them to be body-flexible – to find her attractive when her weight inevitably fluctuates, when she is pregnant, when she is breastfeeding, when she ages. Investing in a family is a long-term commitment for a human male, so he must be able to adapt to his partner’s continually changing body as the years pass.
So when a man says he has not noticed whether his female partner has put on weight, he may simply be telling the truth, and demonstrating a typically male insensitivity to absolute body size inculcated by millions of years of evolution.
In this chapter I hope I have convinced you that men seek profound and important information when they look at women, and that over the generations this has relentlessly sculpted women’s bodies into their present form. However, this leads us to a paradox which lies at the heart of this book. If male desire is so biologically important, why do women think about it so little?
There are few studies which have sought to discover why women wish to look attractive, but they and the anecdotal evidence tell the same story. I have asked many women why they want to look attractive, and the usual answers boil down to wanting to maintain their self-esteem, or wanting to impress other women. Whether or not those two things are the same I will consider later, but both seem more important than the need to impress men. Of course, these responses may reflect the non-confidential and male-originated nature of my enquiries, but there are surveys which back up my findings. They suggest that for women, when it comes to looking good, impressing other women and maintaining self-esteem are each individually at least twice as important as impressing men.
On the surface, this does not make biological sense. We know what men want, we know how this has affected women’s evolution, and we also know that for both women and men finding a sexual partner is one of the most important things in life. And yet, heterosexual women do not seem consciously to be trying to attract men, or at least not very much. I am sure that the urge to impress men changes from time to time in a woman’s life, but in general its apparent unimportance is very striking.
Although it took this whole chapter to discover what men want, it will take the rest of the book to find out why, as far as women are concerned, it does not seem to matter.