The Biology of Beauty

Nancy Etcoff, Survival of the Prettiest: The Science of Beauty (New York: Anchor Books 2000) 

Beauty is in the eye of the beholder.  

This much is true by very definition. After all, the Oxford English Dictionary defines beauty as: 

A combination of qualities, such as shape, colour, or form, that pleases the aesthetic senses, especially the sight’. 

If beauty is in the eye of the beholder, then the ‘eye of the beholder’ has been shaped by a process of natural, and sexual, selection to find certain things beautful — and, if beauty is in the ‘eye of the beholder’, then sexiness is located in a different part of the male anatomy but similarly subjective

Thus, beauty is defined as that which is pleasing to an external observer. It therefore presupposes the existence of an external observer, separate from the person, or thing, that is credited with beauty, from whose perspective the thing or individual is credited with beauty.[1]

Moreover, perceptions of beauty do indeed differ.  

To some extent, preferences differ between individuals, and between different races and cultures. More obviously, and to a far greater extent, they also differ as between species.  

Thus, a male chimpanzee would presumably consider a female chimpanzee as more beautiful than a woman. The average human male, however, would likely disagree – though it might depend on the woman. 

As William James wrote in 1890: 

To the lion it is the lioness which is made to be loved; to the bear, the she-bear. To the broody hen the notion would probably seem monstrous that there should be a creature in the world to whom a nestful of eggs was not the utterly fascinating and precious and never-to-be-too-much-sat-upon object which it is to her” (Principles of Psychology (vol 2): p387). 

Beauty is therefore not an intrinsic property of the person or object that is described as beautiful, but rather a quality attributed to that person or object by a third-party in accordance with their own subjective tastes. 

However, if beauty is then indeed a subjective assessment, that does not mean it is an entirely arbitrary one. 

On the contrary, if beauty is indeed in the ‘eye of the beholder’ then it must be remembered that the ‘eye of the beholder’—and, more importantly, the brain to which that eye is attached—has been shaped by a process of both natural and sexual selection

In other words, we have evolved to find some things beautiful, and others ugly, because doing so enhanced the reproductive success of our ancestors. 

Thus, just as we have evolved to find the sight of excrement, blood and disease disgusting, because each were potential sources of infection, and the sight of snakes, lions and spiders fear-inducing, because each likewise represented a potential threat to our survival when encountered in the ancestral environment in which we evolved, so we have evolved to find the sight of certain things pleasing on the eye. 

Of course, not only people can be beautiful. Landscapes, skylines, works of art, flowers and birds can all be described as ‘beautiful’. 

Just as we have evolved to find individuals of the opposite sex attractive for reasons of reproduction, so these other aspects of aesthetic preference may also have been shaped by natural selection. 

Thus, some research has suggested that our perception of certain landscapes as beautiful may reflect psychological adaptations that evolved in the context of habitat selection (Orians & Heerwagen 1992).  

However, Nancy Etcoff does not discuss such research. Instead, in ‘Survival of the Prettiest’, her focus is almost exclusively on what we might term ‘sexual beauty’. 

Yet, if beauty is indeed in the ‘in the eye of the beholder’, then sexiness is surely located in a different part of the male anatomy, but equally subjective in nature. 

Indeed, as I shall discuss below, even in the context of mate preferences, ‘sexiness’ and ‘beauty’ are hardly synonyms. As an illustration, Etcoff herself quotes that infamous but occasionally insightful pseudo-scientist and all-round charlatan, Sigmund Freud, whom she quotes as observing:  

The genitals themselves, the sight of which is always exciting, are nevertheless hardly ever judged to be beautiful; the quality of beauty seems, instead, to attach to certain secondary sexual characters” (p19: quoted from Civilization and its Discontents). 

Empirical Research 

Of the many books that have been written about the evolutionary psychology of sexual attraction (and I say this as someone who has read, at one time or another, a good number of them), a common complaint is that they are full of untested, or even untestable, speculation – i.e. what that other infamous scientific charlatan Stephen Jay Gould famously referred to as just so stories

This is not a criticism that could ever be levelled at Nancy Etcoff’s ‘Survival of the Prettiest’. On the contrary, as befits Etcoff’s background as a working scientist (not a mere journalist or popularizer), it is, from start to finish, it is full of data from published studies, demonstrating, among other things, the correlates of physical attractiveness, as well as the real-world payoffs associated with physical attractiveness (what is sometimes popularly referred to as ‘lookism’). 

Indeed, in contrast to other scientific works dealing with a similar subject-matter, one of my main criticisms of this otherwise excellent work would be that, while rich in data, it is actually somewhat deficient in theory. 

Youthfulness, Fertility, Reproductive Value and Attractiveness 

A good example of this deficiency in theory is provided by Etcoff’s discussion of the relationship between age and attractiveness. Thus, one of the main and recurrent themes of ‘Survival of the Prettiest’ is that, among women, sexual attractiveness is consistently associated with indicators of youth. Thus, she writes: 

Physical beauty is like athletic skill: it peaks young. Extreme beauty is rare and almost always found, if at all, in people before they reach the age of thirty-five” (p63). 

Yet Etcoff addresses only briefly the question of why it is that youthful women or girls are perceived as more attractive – or, to put the matter more accurately, why it is that males are sexually and romantically attracted to females of youthful appearance. 

Etcoff’s answer is: fertility

Female fertility rapidly declines with age, before ceasing altogether with menopause

There is, therefore, in Darwinian terms, no benefit in a male being sexually attracted to an older, post-menopausal female, since any mating effort expended would be wasted, as any resulting sexual union could not produce offspring. 

As for the menopause itself, this, Etcoff speculates, citing scientific polymath, popularizer and part-time sociobiologist Jared Diamond, evolved because human offspring enjoy a long period of helpless dependence on their mother, without whom they cannot survive. 

Therefore, after a certain age, it pays women to focus on caring for existing offspring, or even grandchildren, rather than producing new offspring whom they will likely not be around to care for (p73).[2]

This theory has sometimes been termed the grandmother hypothesis.

However, the decline in female fertility with age is perhaps not sufficient to explain the male preference for youth. 

After all, women’s fertility is said to peak in their early- to mid-twenties.[3]

However, men’s (and boy’s) sexual interest, if anything, seems to peak in respect of females, if anything, somewhat younger, namely in their late-teens (Kenrick & Keefe 1992). 

To explain this, Douglas Kenrick and Richard Keefe propose, following a suggestion of Donald Symons, that this is because girls at this age, while less fertile, have higher reproductive value, a concept drawn from ecology, population genetics and demography, which refers to an individual’s expected future reproductive output given their current age (Kenrick & Keefe 1992). 

Reproductive value in human females (and in males too) peaks just after puberty, when a girl first becomes capable of bearing offspring. 

Before then, there is always the risk she will die before reaching sexual maturity; after, her reproductive value declines with each passing year as she approaches menopause. 

Thus, Kenrick and Keefe, like Symons before them, argue that, since most human reproduction occurs within long-term pair-bonds, it is to the evoluionaryadvantage of males to form long-term pair-bonds with females of maximal reproductive value (i.e. mid to late teens), so that, by so doing, they can monopolize the entirety of that woman’s reproductive output over the coming years. 

Yet the closest Etcoff gets to discussing this is a single sentence where she writes: 

Men often prefer the physical signs of a woman below peak fertility (under age twenty). Its like signing a contract a year before you want to start the job” (p72). 

Yet the theme of indicators of youth being a correlate of female attractiveness is a major theme of her book. 

Thus, Etcoff reports that, in a survey of traditional cultures: 

The highest frequency of brides was in the twelve to fifteen years of age category… Girls at this age are preternaturally beautiful” (p57). 

It is perhaps true that “girls at this age are preternaturally beautiful” – and Etcoff, being female, can perhaps even get away with saying this without being accused of being a pervert or ‘pedophile’ for even suggesting such a thing. 

Nevertheless, this age “twelve to fifteen” seems rather younger than most men’s, and even most teenage boys, ideal sexual partners, at least in western societies. 

Thus, for example, Kenrick and Keefe inferred from their data that around eighteen was the preferred age of sexual partner for most males, even those somewhat younger than this themselves.[4]

Of course, in primitive, non-western cultures, women may lose their looks more quickly, due to inferior health and nutrition, the relative unavailability of beauty treatments and because they usually undergo repeated childbirth from puberty onward, which takes a toll on their health and bodies. 

On the other hand, however, obesity is more prevalent in the West, decreases sexual attractiveness and increases with age. 

Moreover, girls in the west now reach puberty somewhat earlier than in previous centuries, and perhaps earlier than in the developing world, probably due to improved nutrition and health. This suggests that females develop secondary sexual characteristics (e.g. large hips and breasts) that are perceived as attractive because they are indicators of fertility, and hence come to be attractive to males, rather earlier than in premodern or primitive cultures. 

Perhaps Etcoff is right that girls “in the twelve to fifteen years of age category… are preternaturally beautiful” – though this is surely an overgeneralization and does not apply to every girl of this age. 

However, if ‘beauty’ peaks very early, I suspect ‘sexiness’ peaks rather later, perhaps late-teens into early or even mid-twenties. 

Thus, the latter is dependent on secondary sexual characteristics that develop only in late-puberty, namely larger breasts, buttocks and hips

Thus, Etcoff reports, rather disturbingly, that: 

When [the] facial proportions [of magazine cover girls] are fed into a computer, it guesstimates their age to be between six and seven years of age” (p151; citing Jones 1995). 

But, of course, as Etcoff is at pains to emphasize in the next sentence, the women pictured do not actually look like they are of this age, either in their faces let alone their bodies. 

Instead, she cites Douglas Jones, the author of the study upon which this claim is based, as arguing that the neural network’s estimate of their age can be explained by their display of “supernormal stimuli”, which she defines as “attractive features… exaggerated beyond proportions normally found in nature (at least in adults)” (p151). 

Yet much the same could be said of the unrealistically large, surgically-enhanced breasts favored among, for example, glamour models. These abnormally large breasts are likewise an example of “supernormal stimuli” that may never be found naturally, as suggested by Doyle & Pazhoohi (2012)

But large breasts are indicators of sexual maturity that are rarely present in girls before their late-teens. 

In other words, if the beauty of girls’ faces peaks at a very young age, the sexiness of their bodies peaks rather later. 

Perhaps this distinction between what we can term ‘beauty’ and ‘sexiness’ can be made sense of in terms of a distinction between what David Buss calls short-term and long-term mating strategies

Thus, if fertility peaks in the mid-twenties, then, in respect of short-term mating (i.e. one-night stands, casual sex, hook-ups and other one-off sexual encounters), men should presumably prefer partners of a somewhat greater age than their preferences in respect of long-term partners – i.e. of maximal fertility rather than maximum reproductive value – since in the case of short-term mating strategies there is no question of monopolizing the woman or girl’s long-term future reproductive output. 

In contrast, cues of beauty, as evinced by relatively younger females, might trigger a greater willingness for males to invest in a long-term relationship. 

This ironically suggests, contrary to contemporary popular perception, males’ sexual or romantic interest in respect of relatively younger women and girls (i.e. those still in their teens) would tend to reflect more ‘honourable intentions’ (i.e. more focussed on marriage or a long-term relationship rather than mere casual sex) than does their interest in older women. 

However, as far as I am aware, no study has ever demonstrated differences in men’s preferences regarding the preferred age-range of their casual sex partners as compared to their preferences in respect of longer-term partners. This is perhaps because, since commitment-free casual sex is almost invariably a win-win situation for men, and most men’s opportunities in this arena likely to be few and far between, there has been little selection acting on men to discriminate at all in respect of short-term partners. 

Are There Sex Differences in Sexiness? 

Another major theme of ‘Survival of the Prettiest’ is that the payoffs for good-looks are greater for women than for men. 

Beauty is most obviously advantageous in a mating context. But women convert this advantage into an economic one through marriage. Thus, Etcoff reports: 

The best-looking girls in high school are more than ten times as likely to get married as the least good-looking. Better looking girls tend to ‘marry up’, that is, marry men with more education and income then they have” (p65; see also Udry & Eckland 1984; Hamermesh & Biddle 1994). 

However, there is no such advantage accruing to better-looking male students. 

On the hand, according to Catherine Hakim, in her book Erotic Capital: The Power of Attraction in the Boardroom and the Bedroom (which I have reviewed here, here and here) in the workplace, the wage premium associated with being better looking is actually, perhaps surprisingly, greater for men than for women. 

For Hakim herself: 

This is clear evidence of sex discrimination… as all studies show women score higher than men on attractiveness” (Money, Honey: p246). 

However, as I explain in my review of her book, the better view is that, since beauty opens up so many other avenues to social advancement for women, notably through marriage, relatively more beautiful women corresponding reduce their work-effort in the workplace since they have need of pursuing social advancement through their careers when they can far more easily achieve it through marriage. 

After all, by bother to earn money when you can simply marry it instead. 

According to Etcoff, there is only one sphere where being more beautiful is actually disadvantageous for women, namely in respect of same-sex friendships: 

Good looking women in particular encounter trouble with other women. They are less liked by other women, even other good-looking women” (p50; citing Krebs & Adinolfy 1975). 

She does not speculate as to why this is so. An obvious explanation is envy and dislike of the sexual competition that beautiful women represent. 

However, an alternative explanation is perhaps that beautiful women do indeed come to have less likeable personalities. Perhaps, having grown used to receiving preferential treatment from and being fawned over by men, beautiful women become entitled and spoilt. 

Men might overlook these flaws on account of their looks, but, other women, immune to their charms, may be a different story altogether.[5]

All this, of course, raises the question as to why the payoffs for good looks are so much greater for women than for men? 

Etcoff does not address this, but, from a Darwinian perspective, it is actually something of a paradox which I have discussed previously

After all, among other species, it is males for whom beauty affords a greater payoff in terms of the ultimate currency of natural selection – i.e. reproductive success. 

It is therefore male birds who usually evolve more beautiful plumages, while females of the same species are often quite drab, the classic example being the peacock and peahen

The ultimate evolutionary explanation for this pattern is called Bateman’s principle, later formalized by Robert Trivers as differential parental investment theory (Bateman 1948; Trivers 1972). 

The basis of this theory is this: Females must make a greater minimal investment in offspring in order to successfully reproduce. For example, among humans, females must commit themselves to nine months pregnancy, plus breastfeeding, whereas a male must contribute, at minimum, only a single ejaculate. Females therefore represent the limiting factor in mammalian reproduction for access to whom males compete. 

One way in which they compete is by display (e.g. lekking). Hence the evolution of the elaborate tail of the peacock

Yet, among humans, it is females who seem more concerned with using their beauty to attract mates. 

Of course, women use makeup and clothing to attract men rather than growing or evolving long tails. 

However, behavior is no less subject to selection than morphology, so the paradox remains.[6]

Indeed, the most promising example of a morphological trait in humans that may have evolved primarily for attracting members of the opposite sex (i.e. a ‘peacock’s tail’) is, again, a female trait – namely, breasts

This is, of course, the argument that was, to my knowledge, first developed by ethologist Desmond Morris in his book The Naked Ape, which I have reviewed here, and which I discuss in greater depth here

As Etcoff herself writes: 

Female breasts are like no others in the mammalian world. Humans are the only mammals who develop rounded breasts at puberty and keep them whether or not they are producing milk… In humans, breast size is not related to the amount or quality of milk that the breast produces” (p187).[7]

Instead, human breasts are, save during pregnancy and lactation, composed predominantly of, not milk, but fat. 

This is in stark contrast to the situation among other mammals, who develop breasts only during pregnancy. 

Breasts are not sex symbols to other mammals, anything but, since they indicate a pregnant or lactating and infertile female. To chimps, gorillas and orangutans, breasts are sexual turn-offs” (p187). 

 Why then does sexual selection seem, at least on this evidence, to have acted more strongly on women than men? 

Richard Dawkins, in The Selfish Gene (which I have reviewed here), first alluded to this anomaly, lamenting: 

What has happened in modern western man? Has the male really become the sought-after sex, the one that is in demand, the sex that can afford to be choosy? If so, why?” (The Selfish Gene: p165). 

Yet this is surely not the case with regard to casual sex (i.e. hook-ups and one-night stands). Here, it is very much men who ardently pursue and women who are sought after. 

For example, in one study at a University campus, 72% of male students agreed to go to bed with a female stranger who propositioned them to this effect, yet not a single one of the 96 females approached agreed to the same request from a male stranger (Clark and Hatfield 1989). 

(What percentage of the students sued the university for sexual harassment was not revealed.) 

Indeed, patterns of everything from prostitution to pornography consumption confirm this – see The Evolution of Human Sexuality (which I have reviewed here). 

Yet humans are unusual among mammals in also forming long-term pair-bonds where male parental investment is the norm. Here, men have every incentive to be as selective as females in their choice of partner. 

In particular, in Western societies practising what Richard Alexander called socially-imposed monogamy (i.e. where there exist large differentials in male resource holdings, but polygynous marriage is unlawful) competition among women for exclusive rights to resource-abundant alpha males may be intense (Gaulin and Boser 1990). 

In short, the advantage to a woman in becoming the sole wife of a multi-millionaire is substantial. 

This, then, may explain the unusual intensity of sexual selection among human females. 

Why, though, is there not evidence of similar sexual selection operating among males? 

Perhaps the answer is that, since, in most cultures, arranged marriages are the norm, female choice actually played little role in human evolution. 

Instead, male mating success may have depended less upon what Darwin called intersexual selection and more upon intrasexual selection – i.e. less upon female choice and more upon male-male fighting ability (see Puts 2010). 

Male Attractiveness and Fighting Ability 

Paradoxically, this is reflected even in the very traits that women find attractive in men. 

Thus, although Etcoff’s book is titled ‘The Evolution of Prettiness’, and ‘prettiness’ is usually an adjective applied to women, and, when applied to men, is—perhaps tellingly—rarely a complement, Etcoff does discuss male attractiveness too.  

However, Etcoff acknowledges that male attractiveness is a more complex matter than female attractiveness: 

We have a clearer idea of what is going on with female beauty. A handsome male turns out to be a bit harder to describe, although people reach consensus almost as easily when they see him” (p155).[8]

Yet what is notable about the factors that Etcoff describes as attractive among men is that they all seem to be related to fighting ability. 

This is most obviously true of height (p172-176) and muscularity (p176-80). 

Indeed, in a section titled “No Pecs, No Sex”, though she focuses on the role of pectoral muscles in determining attractiveness, Etcoff nevertheless acknowledges: 

Pectoral muscles are the human male’s antlers. Their weapons of war” (p177). 

Thus, height and muscularity have obvious functional utility. 

This in stark contrast to traits such as the peacock’s tail, which are often a positive handicap to their owner. Indeed, one influential theory of sexual selection contends that it is precisely because they represent a handicap that they have evolved as a sexually-selected fitness indicator, because only a genetically superior male is capable of bearing the handicap of such an unwieldy ornament, and hence possession of such a handicap is paradoxically an honest signal of health. 

Yet, if men’s bodies have evolved more for fighting than attracting mates, the same is perhaps less obviously true of their faces. 

Thus, anthropologist David Puts proposes: 

Even [male] facial structure may be designed for fighting: heavy brow ridges protect eyes from blows, and robust mandibles lessen the risk of catastrophic jaw fractures” (Puts 2010: p168). 

Indeed, looking at the facial features of a highly dominant, masculine male face, like that of Mike Tyson, for example, one gets the distinct impression that, if you were foolish enough to try punching it, it would likely do more damage to your hand than to his face. 

Thus, if some faces are, as cliché contends, highly ‘punchable’, then others are presumably at the opposite end of this spectrum. 

This also explains some male secondary sexual characteristics that otherwise seem anomalous, for example, beards. These have actually been found in some studies “to decrease attractiveness to women, yet have strong positive effects on men’s appearance of dominance” (Puts 2010: p166). 

David Puts concludes: 

Men’s traits look designed to make men appear threatening, or enable them to inflict real harm. Men’s beards and deep voices seem designed specifically to increase apparent size and dominance” (Puts 2010: p168). 

Interestingly, Etcoff herself anticipates this theory, writing: 

Beautiful ornaments [in males] develop not just to charm the opposite sex with bright colors and lovely songs, but to intimidate rivals and win the intrasex competition—think of huge antlers. When evolutionists talk about the beauty of human males, they often refer more to their weapons of war than their charms, to their antlers rather than their bright colors. In other words, male beauty is thought to have evolved at least partly in response to male appraisal” (p74) 

Of course, these same traits are also often attractive to females. 

After all, if a tall muscular man has higher reproductive success because he is better at fighting, then it pays women to preferentially mate with tall, muscular men so that their male offspring will inherit these traits and hence themselves have high reproductive success, helping the spread the women’s own genes by piggybacking on the superior male’s genes.  

This is a version of sexy son theory

In addition, males with fighting prowess are better able to protect and provision their mates. 

However, this attractiveness to females is obviously secondary to the primary role in male-male fighting. 

Moreover, Etcoff admits, highly masculine faces are not always attractive. 

Thus, unlike the “supernormal” or “hyperfeminine” female faces that men find most attractive in women, women rated “hypermasculine” faces as less attractive (p158). This, she speculates, is because they are perceived as overaggressive and unlikely to invest in offspring

As to whether such men are indeed less willing to invest in offspring, this Etcoff does not discuss and there appears to be little evidence on the topic. But the association of testosterone with both physiological and psychological masculinization suggests that the hypothesis is at least plausible

Etcoff concludes: 

For men, the trick is to look masculine but not exaggeratedly masculine, which results in a ‘Neanderthal’ look suggesting coldness or cruelty” (p159). 

Examples of males with perhaps overly masculine faces are perhaps certain boxers, who tend to have highly masculine facial morphology (e.g. heavy brow ridges, deep set eyes, wide muscular jaws), but are rarely described as handsome. 

For example, I doubt anyone would ever call Mike Tyson handsome. But, then, no one would ever call him exactly ugly either – at least not to his face. 

An extreme example might be the Russian boxer Nikolai Valuev, whose extreme neanderthal-like physiognomy was much remarked on. 

Another example that sprung to mind was the footballer Wayne Rooney (also, perhaps not uncoincidentally, said to have been a talented boxer) who, when he first became famous, was immediately tagged by the newspapers, media and comedians as ugly despite – or indeed because of – his highly masculine, indeed thuggish, facial physiognomy

Likewise, Etcoff reports that large eyes are perceived as attractive in men, but these are a neotenous trait, associated with both immature infants and indeed with female beauty (p158). 

This odd finding Etcoff attributes to the fact that large eyes, as an infantile trait, evoke women’s nurturance, a trait that evolved in the context of parental investment rather than mate choice

Yet this is contrary to the general principle in evolutionary psychology of modularity of mind and the domain specificity of psychological adaptations, whereby it is assumed that that psychological adaptations for mate choice and for parental investment represent domain-specific modules with little or no overlap. 

Clearly, for psychological adaptations in one of these domains to be applied in the other would result in highly maladaptive behaviours, such as sexual attraction to infants and to your own close biological relatives.[9]

In addition to being more complex and less easy to make sense of than female beauty, male physical attractiveness is also less importance in determining female mate choice than is female beauty in male mate choice

In particular, she acknowledges that male status often trumps handsomeness. Thus, she quotes a delightfully cynical, not especially poetic, line from the ancient Roman poet Ovid, who wrote: 

Girls praise a poem, but go for expensive presents. Any illiterate oaf can catch their eye, provided he’s rich” (quoted: p75). 

A perhaps more memorable formulation of the same idea is quoted on the same page from a less illustrious source, namely boxing promoter, numbers racketeer and convicted killer Don King, on a subject I have already discussed, namely the handsomeness (or not) of Mike Tyson, King remarking: 

Any man with forty two million looks exactly like Clark Gable” (quoted: p75). 

Endnotes

[1] I perhaps belabor this rather obvious point only because one evolutionary psychologist, Satoshi Kanazawa, argues that, since many aspects of beauty standards are cross-culturally universal, beauty standards are not ‘in the eye of the beholder’. I agree with Kanazawa on the substantive issue that beauty standards are indeed mostly cross-culturally universal among humans, albeit not entirely so). However, I nevertheless argue, perhaps somewhat pedantically, that beauty remains strictly in the ‘eye of the beholder’, but it is simply that the ‘eye of the beholder’ (and the brain to which is attached) has been shaped by a process of natural selection so as to make different humans share the same beauty standards. 

[2] While Jared Diamond has indeed made many original contributions to many fields, this idea does not in fact originate with him, even though Etcoff oddly cites him as a source. Indeed, as far as I am aware, it is even especially associated with Diamond. and may actually have been originated by another, lesser known, but arguable even more brilliant evolutionary biologist, namely George C Williams (Williams 1957). 

[3] Actually, pregnancy rates peak surprisingly young, perhaps even disturbingly young, with girls in their mid- to late-teens being most likely to become pregnant from any single act of sexual intercourse, all else being equal. However, the high pregnancy rates of teenage girls are said to be partially offset by their greater risk of birth complications. Therefore, female fertility is said to peak among women in their early- to mid-twenties.

[4] This the authors of the study inferred from, among other evidence, an analysis of lonely hearts advertisements, wherein, although the age of the female sexual/romantic partner sought was related to the advertised age of the man placing the ad (which Kenrick and Keefe inferred was a reflection of the fact that their own age delimited the age-range of the sexual partners whom they would be able to attract, and whom it would be socially acceptable for them to seek out) nevertheless the older the man, the greater the age-difference he sought in a partner. In addition, they reported evidence of surveys suggesting that, in contrast to older men, younger teenage boys, in an ideal world, actually preferred somewhat older sexual partners, suggesting that the ideal age of sexual partner for males of any age was around eighteen years of age. 

[5] Etcoff also does not discuss whether the same is true of exceptionally handsome men – i.e. do exceptionally handsome men, like beautiful women, also have problems maintaining same-sex friendships. I suspect that this is not so, since male status and self-esteem is not usually based on handsomeness as such – though it may be based on things related to handsomeness, such as height, athleticism, earnings, and perceived ‘success with women’. Interestingly, however, French novelist Michel Houellebecq argues otherwise in his novel, Whatever, in which, after describing the jealousy of one of the main characters, the short ugly Raphael Tisserand, towards an particularly handsome male colleague, writes: 

Exceptionally beautiful people are often modest, gentle, affable, considerate. They have great difficulty in making friends, at least among men. They’re forced to make a constant effort to try and make you forget their superiority, be it ever so little” (Whatever: p63) 

[6] Thus, in other non-human species, behaviour is often subject to sexual selection, in, for example, mating displays, or the remarkable, elaborate and often beautiful, but non-functional, nests built by male bowerbirds, which Geoffrey Miller sees as analogous to human art. 

[7] An alternative theory for the evolution of human breasts is that they evolved, not as a sexually selected ornament, but rather as a storehouse of nutrients, analogous to the camel’s humps, upon which women can draw during pregnancy. On this view, the sexual dimorphism of their presentation (i.e. the fact that, although men do have breasts, they are usually much less developed than those of women) reflects, not sexual selection, but rather the calaric demands of pregnancy. 
However, these two alternative hypotheses are not mutually incompatible. On the contrary, they may be mutually reinforcing. Thus, Etcoff herself mentions the possibility that breasts are attractive precisely because: 

Breasts honestly advertise the presence of fat reserves needed to sustain a pregnancy” (p178.) 

On this view, men see fatty breasts as attractive in a sex partner precisely because only women with sufficient reserves of fat to grow large breasts are likely to be capable of successfully gestating an infant for nine months. 

[8] Personally, as a heterosexual male, I have always had difficulty recognizing ‘handsomeness’ in men, and I found this part of Etcoff’s book especially interesting for this reason. In my defence, this is, I suspect, partly because many rich and famous male celebrities are celebrated as ‘sex symbols’ and described as ‘handsome’, even though their status as ‘sex symbols’ owes more to the fact they are rich and famous than their actual looks. Thus, male celebrities sometimes become ‘sex symbols’ despite their looks, rather than because of it. Many famous rock stars, for example, are not, I feel especially handsome. In contrast, men did not suddenly start idealizing physically unattractive female celebrities as ‘sex symbols’, or as beautiful, simply because they are famous celebrities, howsoever rich and famous they may become. 
Add to this the fact that much of what passes for good looks in both sexes is, ironically, normalness – i.e. a lack of abnormalities and averageness – and identifying which men women consider ‘handsome’ had, before reading Etcoff’s book, always escaped me.
However, Etcoff, for her part, might well call me deluded. Men, she reports, only claim they cannot tell which men are handsome and which are not, perhaps to avoid being accused of homosexuality: 

Although men think they cannot judge another man’s beauty, the agree among themselves and with women about which men are the handsomest” (p138). 

Nevertheless, there is indeed some evidence that judging male handsomeness is not as clear cut as Etcoff seems to suggests. Thus, it has been found that, not only do men claim to have difficulty telling handsome men from ugly men, but also women themselves are more likely to disagree among themselves about the physical attractiveness of members of the opposite sex as compared to men (Wood & Brumbaugh 2009Wake Forest University 2009). 
Indeed, not only do women not always agree with one another regarding the attractiveness of men, sometimes they can’t even agree with themselves. Thus, Etcoff reports: 

A woman makes her evaluations of men more slowly, and if another woman offers a different opinion, she may change her mind” (p76). 

This indecisiveness, for Etcoff, actually makes good evolutionary sense:

If women take a second look, compare notes with other women, or change their minds after more thought, it is not out of indecisiveness but out of wisdom. Mate choice is not just about fertility—most men are fertile most or all of their lives—but about finding a helpmate to bring up the baby” (p77). 

Another possible reason why women may consult other women as to whether a given man is attractive or not is sexy son theory
On this view, it pays for women to mate with men who are perceived as attractive by other women because then any offspring whom they bear by these men will likely inherit the very traits that made the father attractive to women, and hence themselves be attractive to women and hence be successful in spreading the woman’s own genes to subsequent generations. 
In other words, being attractive to other women is itself an attractive trait in a male. However, sexy son theory is not discussed by Etcoff.

[9] Another study discussed by Etcoff also reported anomalous results, finding that women actually preferred somewhat feminized male faces over both masculinized and average male faces (Perrett et al 1998). However, Etcoff cautions that: 

The Perrett study is the only empirical evidence to date that some degree of feminization may be attractive in a man’s face” (p159). 

Other studies concur that male faces that are somewhat, but not excessively, masculinized as compared to the average male face are preferred by women. 
However, one study published just after the first edition of ‘Survival of the Prettiest’ was written, holds the possibility of reconciling these conflicting findings. This study reported cyclical changes in female preferences, with women preferring more masculinized faces only when they are in the most fertile phase of their cycle, and at other times preferring more feminine features (Penton-Voak & Perrett 2000). 
This, together with other evidence, has been controversially interpreted as suggesting that human females practice a so-called dual mating strategy, preferring males with more feminine faces, supposedly a marker for a greater willingness to invest in offspring, as social partners, while surreptitiously attempting to cuckold these ‘beta providers’ with DNA from high-T alphas, by preferentially mating with the latter when they are most likely to be ovulating (see also Penton-Voak et al 1999Bellis & Baker 1990). 
However, recent meta-analyses have called into question the evidence for cyclical fluctuations in female mate preferences (Wood et al 2014; cf. Gildersleeve et al 2014), and it has been suggested that such findings may represent casualties of the so-called replication crisis in psychology
While the intensity of women’s sex drive does indeed seem to fluctuate cyclically, the evidence for more fine-grained changes in female mate preferences should be treated with caution. 

References 

Bateman (1948), Intra-sexual selection in DrosophilaHeredity, 2(3): 349–368. 
Bellis & Baker (1990). Do females promote sperm competition?: Data for humansAnimal Behavior, 40: 997-999. 
Clark & Hatfield (1989) Gender differences in receptivity to sexual offers. Journal of Psychology & Human Sexuality, 2(1), 39–55 
Doyle & Pazhoohi (2012) Natural and Augmented Breasts: Is What is Not Natural Most Attractive? Human Ethology Bulletin 27(4):4-14. 
Gaulin & Boser (1990) Dowry as Female Competition, American Anthropologist 92(4):994-1005. 
Gildersleeve et al (2014) Do women’s mate preferences change across the ovulatory cycle? A meta-analytic reviewPsychological Bulletin 140(5):1205-59. 
Hamermesh & Biddle (1994) Beauty and the Labor Market, American Economic Review 84(5):1174-1194.
Jones 1995 Sexual selection, physical attractiveness, and facial neoteny: Cross-cultural evidence and implications, Current Anthropology, 36(5):723–748. 
Kenrick & Keefe (1992) Age preferences in mates reflect sex differences in mating strategies. Behavioral and Brain Sciences 15(1):75-133. 
Orians & Heerwagen (1992) Evolved responses to landscapes. In Barkow, Cosmides & Tooby (Eds.), The Adapted Mind: Evolutionary Psychology and the Generation of Culture (pp. 555–579). Oxford University Press. 
Penton-Voak et al (1999) Menstrual cycle alters face preferencesNature 399 741-2. 
Penton-Voak & Perrett DI (2000) Female preference for male faces changes cyclically: Further evidence. Evolution and Human Behavoir 21(1):39–48. 
Perrett et al (1998) Effects of sexual dimorphism on facial attractiveness. Nature 394(6696):884-7. 
Puts (2013) Beauty and the Beast: Mechanisms of Sexual Selection in Humans. Evolution and Human Behavior 31(3):157-175. 
Wake Forest University (2009) Rating Attractiveness: Consensus Among Men, Not Women, Study Finds. ScienceDaily. ScienceDaily, 27 June 2009. 
Trivers (1972) Parental investment and sexual selectionSexual Selection & the Descent of Man, Aldine de Gruyter, New York, 136-179. Chicago. 
Williams (1957) Pleiotropy, natural selection, and the evolution of senescence. Evolution. 11(4): 398–411. 
Wood & Brumbaugh (2009) Using Revealed Mate Preferences to Evaluate Market Force and Differential Preference Explanations for Mate Selection, Journal of Personality and Social Psychology 96(6):1226-44.
Udry & Eckland (1984) Benefits of Being Attractive: Differential Payoffs for Men and Women, Psychological Reports 54(1):47–56.
Wood et al (2014). Meta-analysis of menstrual cycle effects on women’s mate preferencesEmotion Review, 6(3), 229–249.  

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