Bryan Caplan  

Age, Sex, Looks, and Attraction: A Puzzle for Evolutionary Psychology

Theory X?... Morality, Rhetoric, and Politi...
I finally read Robert Wright's modern classic The Moral Animal.  I've got lots to say, but let me start with a simple puzzle I never noticed before.  Evolutionary psychology has a simple explanation for why men value women's youth far more than the reverse: Menopause.  Females' fertility declines sharply during their thirties, and largely vanishes in their forties.  Males' fertility, in contrast, declines more slowly, and does not asymptote to zero.  We're largely the descendants of men who liked young women, and woman who weren't so picky about men's age.

So far, so good.  But this story fails to explain another key stylized fact: Conditioning on age, men care more about looks than women.  Since age and looks are strongly negatively correlated for women, it's easy to treat age and looks as a single package.  But they're distinct.  A person can look very young and very ugly at the same time.  So why do men care so much about how women look, strongly preferring a beautiful 25-year-old to a plain 25-year-old?

Before you answer, note that in many species, this pattern reverses.  For lions, ducks, peacocks, and more, it's the males who have seemingly inconvenient adornments, and the females who are plain.

What's your explanation?  Please stick to explanations consistent with evolutionary psychology.

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COMMENTS (33 to date)
aretae writes:

Fertility is also heavily associated with body shape. Fertility is, IIRC, almost perfectly tracked by hip-waist ratio.

Facial attractiveness...the top physical cue for men's long-term partner strategies, beating out even hip-waist a tremendously good marker for bacterial resistance.

Given (a) the insanely large human investment in offspring and (b) the high frequency of death during childbirth, mostly via infection, it isn't at all surprising that the female is judged heavily by looks.

Further, male success (as a hunter/provider/leader) in the Evolutionarily Stable Environment is directly observable, thus leading to status as a/the dominant marker for men, overshadowing looks.

OneEyedMan writes:

High parental contribution by human males makes it costly to reproduce with unfit partners. Appearance is highly sensitive to parasites and nutrition, especially in the natural state, so this is a way of telling if the females are also fit and not just fertile.

This is also consistent with the lowering of standards in the absence of expectations of parental contribution. Men are often willing to have low commitment sex with lower fitness and status women.

In contrast, for lions, ducks, peacocks, male contribution is very low and so the male's primary contribution is DNA and therefore he has little reason to be choosy.

AMW writes:

Perhaps in humans, males contribute substantially more toward insuring the survival and reproduction of offspring than they do in other species. (For example, we know that single human mothers are, on average, at a big wealth disadvantage to married mothers.) Among a lot of other species, even females that have long-term mates pretty much operate as single parents.

Ray writes:

A couple of possibilities (not mutually exclusive)

1. Beauty correlates with health. (No one finds a cachectic ill person pretty). And health correlates with being able to carry a parasitic fetus for 9 months, and still have enough energy left over to raise it for 2 decades.

2. Beauty correlates with being foreign or different genetically

3. Beauty correlates with having a body that can carry a fetus to term.

As to why it's women versus men, a part of that answer might just be: because it has to be someone. There's a division of labor and men have taken on other roles.

Also, it is men who do most of the seeking. They ask for the first date. The ones who wait to be asked out are the ones who have to compete on looks. Notice how much more attention gay men pay to their looks.

Daniel Kuehn writes:

"Adornment" requires maintenance. If a male animal can maintain vibrant plummage it means he's not getting it knocked out in fights. He is able to dominate his opponents. Well adorned males are also healthy enough to maintain lush plummage, which means they have no trouble providing food and other needs.

Human adornment in terms of superficial/external ornamentation (I'm not sure exactly how you mean "adornment") implies a wealth or leisure necessary to maintain that ornamentation. So why adornment in human females rather than males? Gestation and development time. Human development is a lot longer than development time for other animals, and women are the ones with the mammary glands. It's the men that you have to cajole into sticking around. It's the men that need to be convinced. So it's the men that need to be impressed. When child development is quicker extended male presence may not be as necessary so there's no incentive or need to impress him.

Chris T writes:

People's beauty preferences correlate strongly with symmetry. Achieving symmetry is difficult biologically and requires a lot to go right developmentally. High symmetry indicates a high likelihood of good reproductive fitness.

Ruy Diaz writes:

Lions 'looks' may not be directed at females, but towards intimidating other males--the same function of the primate male beard.

The other species you mention are ones where the females chooses the mate, then does the work of raising the offspring, so, the genes is all she gets--hence the importance of looks.

As to why men are choosier about looks regardless of age.... I'm not so sure. Some females of the species have a thing for flings with very attractive males, while being choosier for long-term partners.

Peter writes:

Yes, yes, fertility signals, health signals, all important.

But also consider the impulse to protect and care for things that are "cute": babies, baby animals like big-eyed puppies and kittens. Cute things trigger protective and adoring instincts that accompany higher survival outcomes.

The capacity to inspire endearment is a survival trait all its own; consider make-up, fashion, etc. Related: the phrase, "She has a 'great personality' is acknowledgment of the circumvention of a female lacking in cuteness or beauty by being endearing or companionable despite her apparent unattractiveness.

Ugly things, the ugly stepchild for example, blunt those instincts and contribute to neglect, abuse, indifference.

David MacRae writes:

It helps to think about what is unique about our species - and there are a lot of things which are quite unusual. You've already mentioned one: it's the female who wears the fancy plumage whereas in every other species that has this kind of sex distinction, it invariably is the male.

The purpose of secondary sex characteristics is normally to attract a mate and it is reasonable to think that this is the case for our species too, especially as it is obvious that men are indeed attracted to beautiful women.

Another way that we are unique is our mating patterns. Pre-agricultural societies are polygamous (one man might have as many as four wives). While there are plenty of other polygamous species, we are the only one where the male makes a significant contribution to rearing the young. There are monogamous species where this happens but we are the only polygamous one.

As hunters with weapons, human males are unique in that they are capable of providing for several families at once. The males of all other species either don't get involved in caring for the young at all or they have only one family with a single mate. Good hunters and leaders get multiple women and so pass on their genes. Bad ones will only get one - if even that.

Not surprisingly, it turns out that the conventional explanation is the right one. Women are attracted to a man who is powerful and who will be a good provider for her children. Men are attracted to women who appear to have good genes and to be able to bear many babies. As for the question of the age difference, it's really quite simple to explain. Women want someone who has demonstrated his abilities to provide and to lead. Either a young man with good potential or an older one who has already established himself should do quite nicely. His exact age is not especially important.

And why do men like them young? Well the thing is that older women presumably would already have had several children. Why would he want to provide for another man's kids?

This leads into the question of menopause. First off, most species do not experience this phenomenon so the notion that its the reason for age differences simply doesn't hold water. On the contrary, it must have some adaptive purpose in our species precisely because it's unusual.

One idea advanced is that menopause serves to create the institution of grandmother. The old woman may no longer be attractive to men and her mate may be past the point of being able to support her anyway (assuming he's survived this long; primitive men frequently die from injuries in the hunts or the wars). Despite that, she still is quite capable of helping take care of her grandchildren and thus passing her genes on that way.

Another difference between us and other species is that our young are reared communally by the entire village.

Rachel writes:

For virtually all of human history, age was unknown and unknowable. Even nowadays, age is reported with a lot of error. Therefore, a rational man would definitely prefer a 25-year-old woman who looks 25 to a 25-year-old woman who looks 45.

Douglass Holmes writes:

Although there seems to be no evolutionary advantage to raising someone else's child, there is an advantage to selecting a woman who already has at least one child; she has proven her fertility. Yet men will usually go for the young woman with no children who may not survive childbirth and avoid a woman with at least one child, even though she has proven her ability to bear children. Why do women go for a mate who has proven to be capable of providing while men seem to prefer taking a chance on the young, beautiful, and unproven child-bearer?

Jason Collins writes:

Males typically have adornments as fitness indicators as they are the ones competing to be selected by females. As males are able to impregnate more than one female and may have a small role in child raising, females are typically choosy while males are not. There generally needs to be an element of handicap in the signal for it to be reliable (read the Handicap Principle by Amotz and Avishag Zahavi for a great discussion of this, although it is also covered nicely in Matt Ridley's the Red Queen). The animal examples given fall into this category.

As humans have a lower level of polygamy (during our evolution, our typical pattern was serial monogamy), there is not this bias in fitness indicators. That is not to say they are not present. Geoffrey Miller makes a strong argument in The Mating Mind that the brain could be a fitness indicator, while conspicuous consumption by males could certainly fall into this category. The lower level of polygamy increases the choosiness of the male human as they are required to invest more in offspring and may be restrained in their ability to attract other women.

However, the main distinction that should be made is that female beauty is not an adornment as described above. In experiments, humans generally rate an average of two faces (computer generated) higher than the unusual or unique individual face. This contrasts to the preference for the extreme in most signalling contests between males. Beauty probably indicates features such as a low mutation burden or an absence of parasites and disease.

You could also consider a Fisherian basis for beauty, whereby a preference (with a possibly weak link to fitness) arises and aberration from this preference dooms the plain children to a life alone.

Paavo Ojala writes:

How distinct are beauty and age. They are not the same, but I'm pretty sure that people tend to assume ugly people to be older than they are.

Manly features make women look older. Things that are considered ugly are also signs of age: bad skin, obesity.

Consider cartoon women. My hypothesis is that for syndicated newspaper cartoons cues for ugliness and oldness are the same (especially for women). These are: small eyes, big nose, prominent chin and obesity. (Wrinkles and asymmetry are harder to draw naturally and are only used in extreme cases. Asymmetry is probably more often cue for craziness.)

" A person can look very young and very ugly at the same time."
It would be interesting to find examples of these young uglies and find out what makes them ugly.

agnostic writes:

Preferring young over middle-aged tells you who is fertile vs. barren.

Preferring beautiful over plain or ugly, conditioning on age, tells you who is healthier. That could be due to higher genetic quality, so that you're looking for who has the most robust genes to give your offspring. Or it could be due to environmental differences like not living in such a pathogen-ridden area, which would tell you who has a cleaner environment to rear your children in.

Jason Collins writes:

Having referred to Matt Ridley's The Red Queen earlier in the context of the handicap principle, I should mention that the remainder of the book deals explicitly with the issues of monogamy and polygamy in humans and the uses of beauty. I rate it as Ridley's best book.

RHa writes:

The Mating Mind by Geoffrey Miller is a great book. Attractiveness indicates health. The peacock must be really free of mutation for everything to go right with his tail.

Hyena writes:

Beauty is a status signal. Standards of beauty around the world reduce to expressing a high socio-economic class.

The standard of beauty itself is culturally constructed around high-status indicators. What evolutionary psychology has determined is that people will prefer whatever attaches to the brainspace it has set aside for it.

We select for beauty because wealthier families have more resources. They can better ensure our reproductive success and will have a genetic stake in it.

Hyena writes:

Also, to untie your Gordian knot of fitness indicators: men should carry a different set of signals based on the division of labor.

In the West, men should come with four indicators: his family's wealth, his wealth, his potential to gather wealth, his fertility.

In the West, women should come with two: her fertility and her family's wealth.

So men look at two signals, women at four. We should expect that men would rate both their signals far more highly than women rate any one of theirs. We should also expect women to be more interested in what their mates do and what they have.

This construction benefits from predicting something we do see: women being attracted to men who accomplish things. You hang those pelts from your belt, baby.

Henry writes:
Why do women go for a mate who has proven to be capable of providing while men seem to prefer taking a chance on the young, beautiful, and unproven child-bearer?

Some theories:

a) Women with children have been sexually active, women without children might not have been. The former has an increased chance of sperm competition with other males.

b) If the couple pair up for a longer term, the woman may insist the man care for all of her children, including the step-children. This imposes costs on the male that he could have used instead on his biological children.

c) If the male disappears from the scene, the female has to raise the man's biological child as well as any other children she may have. The more children he has, the more her resources are divided. Hence a man's biological child will get more resources from a woman with no other children than one who has to divide her resources amongst several others.

b) and especially c) can be compensated for if the woman and/or her family is wealthier. Thus, we should see the penalty for an existing child reduced as woman's resources increase. I'm not sure how easily testable this is without a controlled experiment.

Lars P writes:

So why do men care so much about how women look, strongly preferring a beautiful 25-year-old to a plain 25-year-old?

Aside from the valid points about "beauty" indicating health and non mutant status, it is also in large degree created by the woman herself.

That is, smart and capable women can make themselves look good in a lot of big and small ways, so "beauty" also indicates those genetic properties.

Kev writes:

This is an easy one, ev. psychologists have understood this for a while.

Animals with high degrees of male display (peacocks, pheasants, etc.) have lower degrees of commitment to offspring. Because the male's commitment is all based on gene quality, females care exclusively about fitness indicators, so males compete with exaggerated versions of those cues.

The human analogue of this situation is short-term mating. Men seeking short-term mating focus on being attractive and having a sexy personality. Men also are also less concerned with female beauty if they don't need to make a commitment (i.e. if sex is offered for free).

However, in marriage markets, men are demanding of attractiveness (not to waste resources on women who will bear sickly babies). Women care about commitment cues more than attractiveness in marriage markets.

Basically humans have complex mixed mating strategies (short-term and long-term), which other animals lack.

Jason Malloy writes:

Dr. C,

Differential male preference for looks is mostly conditional on culture and type of mating. Long-term mating favors men, and puts sexual selection pressures on women (i.e. women who seek long-term investment are subject to male choosiness). This is the mating culture of make-up, jewelry, and peacocking females white Europeans are most familiar with.

On the other hand, short-term mating leads to choosy women, and more indiscriminate male choice (promiscuous men relax their standards in comparison to monogamous men). Here is where the men resort to the jewelry and make-up peacocking, and it's not difficult to find cultures where the standard animal model holds. Just look at the cast of Jersey Shore: a good example of a short-term mating culture. Which gender on that show spends more time on their physical appearance?

You see a similar pattern in the tropical hoe cultures of sub-Saharan Africa and Papua New Guinea.

Miguel Madeira writes:

"Pre-agricultural societies are polygamous"

I think polygamy is more a trait of agricultural societies than of pre-agricultural societies (in H/G societies there were few man "rich" enough to maintain more than one family).

mick writes:

The traits might also be selectively neutral code arising from mutation that had no reason at all. Darwinism is like Newtonianism, it's a good start, but there is a lot more to evolution and physics than the clockwork universe where everything has a purpose.

Troy Camplin writes:

You are mistaken that males are the ones doing the selecting. Certainly males have a preference for youth and health signals -- of which physical beauty is a significant indicator -- but females too have preferences. They choose males that demonstrate competence and ability to support offspring. In a species such as our where intelligence is what helps us survive, there has to be intelligence indicators. Artistic abilities and the ability to create songs and poetry and music are indications of intelligence (this is why male rock and country have historically been found to be so sexy). Dance also falls into this category, with physical prowess added to it. Then add various demonstrations of strength. We see all of these in any number of traditional festivals -- and the demonstrations are dominated by males. Those who are successful at acquiring things can of course buy fancy objects which demonstrate their success, which further act as signals for women. And if you can combine them? (Well, we're back to rock stars again.) Women are the ones selecting -- far, far more than are men. (Don't believe me? Then why do bars have Ladies Night, during which time they get drinks for free? Men don't need such enticements, as they are less picky about who shows up.)

dullgeek writes:

I have two reactions to this.

1) Men don't just want children. They want grandchildren. So they select women who will have a liklihood of producing attractive children who will have an increased liklihood of breeding. The preference for children, however, trumps the preference for grandchildren. Which is why men "settle" and will pursue an opportunity for sex with a less attractive woman if the more attractive woman is not available. They'd rather have a greater chance at ugly children than a lower chance at beautiful children.

2) I agree w/Troy Camplin. It really isn't the men doing the selecting. In fact, I only think that the female of the human species appears to be adorned from within the species. It's not hard to imagine being a sentient non-human and concluding that the increased male musculature, height and physical prowess indicate a stronger male adornment. And that the females are smaller and more plain looking. As a male in the species, those cues are non-male cues. We're attracted to the lack of adornment of females.

Females, on the other hand, are selecting not only on the physical adornments of the male, but also social adornments - wealth. Men pursue expensive toys because they act as adornments to women, who are really looking for men to be able to demonstrate their wealth.

Matt writes:

There is a probably a lot of different explanations.

1)A women's beauty isn't an inconvenient status symbol. I would liken a peacock's feathers more to a BMW a man can't afford than to a women's pretty face.

2)Who made the joke that babies are cute so that we don't eat them? The same logic could be applied to women. They are attractive so we don't beat them- they are biologically weaker.

3)Symmetry is often associated with good looks. We evolved to find assymetry unnattractive because someone with one eyeball and an extra foot growing out of their left temple is genetically inferior. Our sensual accuity tells us there is a large difference between a plain looking girl and Rachel McAdams, but really there is not. Last time I checked, ugly people still reproduce.

Floccina writes:

In a state of nature very very few older women are good looking?

GregS writes:

Perhaps it's a form of signalling to spurn unattractive women. A male may be saying to the attractive women, "I am so certain of the health of my genes, I can afford to spurn the women I find ugly."

Healthy males can afford to engage in this activity, and unhealthy males cannot. I think those are the conditions necessary for signalling to be useful.

I've heard that men become more attractive to women when they are in a relationship (contrasted with the same male being chronically single); I suspect that being in a relationship is like having someone vouch for you. You are suddenly in greater demand when women realize that someone finds you tolerable/attractive. Having a relationship with an attractive female is like having someone with good genes vouch for your good genes. It may be a useful strategy to have ONLY attractive women vouching for your good genes.

Dan writes:

Beauty is generally a good proxy for not only age but also health and, thus, fertility. How beauty is generally defined isn't completely independent of those more evolutionarily important features. Since natural selection works by acting on groups, the signs generally correlated with being more fertile and healthy such as good skin, youth, fitness, etc will compose what we consider beautiful. Our brains are constructed in a way that uses shortcuts to facilitate decision making; thus, we prefer a beautiful 25 year-old over a plain one.

thomas writes:

Observation 1:
In our society, we make the assumption that men have to be enslaved if they are to be good parents. This assumption is made explicit in family law.
Most evolutionary psychology arguments are based on the idea that a man selects a woman for her health because he is going to make a major commitment to her and her children (at a time long before family law).
It appears to me that at least one of these belief sets must be wrong.

Observation 2:
While men do make a big commitment to children, women's commitment is still bigger. Status isn't enough in a woman's partner, because before the invention of pension funds she couldn't inherit his wealth - he had to stay alive to keep providing. This means that women must have had an even greater interest in the youth and health of their partners than men did.
This suggests to me that the whole men-seek-young-healthy connection is simply the wrong way to think about this.

Observation 3:
If I posit that women take the lead in this dance, and men react, a lot of it all makes sense. I also propose that it is not the man who values the youth and health of the woman so much as it is the woman who values her own youth and health: a woman wants to be sexually active when she is young and healthy, and not so much as she gets older. How does she (or, at least, her body) arrange this?
The answer is "cuteness". Both men and women react to "cuteness" (as someone else has observed above). Humans react to "cute" by wanting to be around, and protect anyone/anything "cute" - in humans that would mean big eyes, small noses, clear skin, high-pitched voice, small(er) physical size. Babies and children use "cute" to get adults - particularly women but in practice all adults - to watch and protect them. Young women re-use that "cute" reaction, but they are seeking to use it on adult men (and for a rather different outcome).

When a woman is young and healthy and can have babies at low risk, she looks "cute". This causes men to be drawn to her, to want to protect her and to be around her all the time - many of the same instincts women have toward children. (Of course, it also leads to a small percentage of men getting confused about the age of the people they should be mating with - but now at least we have an explanation for that anomaly.)

As the woman gets older and has had children, the evolutionary calculus changes: she has children and will soon have/already has grandchildren, and she can contribute more to her own genetic future by helping the existing brood (in "grandmother mode") than by risking her life to have just... one... more. Thus, menopause. However, if she's not going to have children, then being pursued, and even physically controlled by protective males is a problem, so she also alters her appearance and stops looking "cute." Men respond by leaving her alone.

So, the rules are simple. Men, like women, feel protective and associative urges toward people who are "cute." Women use this to attract men when the women are young and want to breed, and they stop looking "cute" to stop attracting men when breeding (and attention from men) is less advantageous - and men simply respond to the signals given.

Today, men lose interest in their middle-aged wives, not because the men have changed, but because their wives have. (Recall the old joke that when a man and a woman marry, she hopes he'll change and he hopes she won't - and both will be disappointed.)

Of course, there are young women who never look "cute." Some of them can't because they are fundamentally unhealthy; in some it's probably just a minor "mistake." They get overlooked as an evolutionary error, in this theory, or may adopt compensating behaviors.

This is not to deny that the subjective experience can be a miserable one for a middle-aged women as she finds men losing interest in her (and for a loving middle-aged man who finds himself realizing he is no longer all that attracted to his wife). Then again, our bodies subject us to some very unsettling experiences in pursuit of their own genetic goals, as any of us can remember on thinking back to the teenage years.

lemmy caution writes:

Kev is right. Animals where the male does not invest in the raising of the offspring don't particularly care about the attractiveness of the female. Men, even for outside pair bonding sex, do care about the attractiveness of the women. Once a baby is born, men do typically provide some resources even if the parents are not pair bonded.

Ewing writes:

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