Why Beautiful People Have More Daughters: Summary

why beautiful people have more daughters

Why Beautiful People Have More Daughters (2007) provides answers to difficult and politically incorrect questions through the lens of evolutionary psychology.


About The Authors:
Satoshi Kanazawa is an American-born British evolutionary psychologist and writer. He focuses on evolutionary psychology to analyze trends and issues pertaining to society, people, and mating choices. 
Miller was a social psychology professor. He died before the publication of the book, so most of the writing belongs to Kanazawa.

Introduction: Avoiding Naturalistic and Moralistic Fallacies

The authors begin by saying that human behavior is a mixture of human nature, culture, and unique experiences. 

The recent trend has been to discount human nature, though, so the authors often stress how the “standard social science model” gets it wrong when it doesn’t account for human nature as shaped by evolution (also see: “The Blank Slate“).

However, when analyzing human behavior from an evolutionary point of view, we must avoid falling for these two fallacies:

  • Naturalistic fallacy: the belief that what is natural is good and that what it is ought to be -and stay that way-
  • Moralistic fallacy: the belief that what’s “fair” or “moral” is how things really are. What ought to be is how nature actually is

Conservatives are more likely to commit the naturalistic fallacy, while liberals are more likely to commit the moralistic fallacy. 

And since academics and social scientists are much more frequently liberals, the moralistic fallacy has been a much greater issue for the social sciences.

A Note on Stereotypes

The authors say it would be easy to dismiss their claims as stereotypes.

But “stereotype” doesn’t mean that there is no truth in the generalization. They say:

Many stereotypes are empirical generalizations with a statistical basis and thus on average tend to be true.
The only problem with stereotypes and empirical generalizations is that they are not always true for all individual cases.

The authors then take another swipe at the social sciences:

Cultural Diversity Is A Myth

And when it comes to culture, the authors say, deep down, all human cultures are essentially the same (also read: why cross-cultural communication is a waste of time).

The recent history of the social sciences is shameful, say the authors.
The social sciences went on a quest to find “different cultures” just so they could “prove” that all human behavior is culturally determined.

And every time a new culture that seemed different than the Western culture could be found, it was a big celebration, so we could blame all our deviances on capitalism or on greed.

But every time, the “different” culture turned out to be a hoax or really quite similar to any other human culture.
Three such examples:

  • Samoa and Margaret Mead (Mead had been taken for a ride)
  • The Gentle Tasaday (a response to Chagnon’s “Yanomamö: The Fierce People”) turned out to be a hoax or, at least, not what they were rumored to be
  • Native American Environmentalism: some authors, including Jared Diamond, bought into the idea Native Americans protected the environment, but it’s not true

The Savannah Principle: How We Grew Maladapted

The Savannah Principle states that the human mind has difficulties comprehending the modern environment.

We have evolved in a much different environment, and progress has been so fast that we haven’t truly adapted to it.

In some cases, our old Savannah brain can lead to maladaptive behavior in our modern environment.
Some examples:

  • Sugar, fats, food: we have too much today and we tend to over-consume
  • Pornography: our mind can’t tell that the images are not real women
  • Paradox of choice in mating: images and dating apps make us believe there are more options and higher quality than there really are
  • TV series “friends”: watching the same show over and over again, we feel like we know the characters and think we have a larger social circle and more friends

Now let’s get down to the Q&As:

Why Are Men And Women So Different?

Two simple biological facts make men and women different:

  • Anisogamy: the female sex cell is larger, more costly, and more “precious.”
  • Internal gestation: women can produce far fewer offspring than men

Anisogamy and internal gestation lead to very large sexual differences in fitness variance.
Fitness variance is the difference between the “winners” and “losers” in the reproductive game. In simple terms, that means that men can either be big losers and not reproduce or be big winners and leave a large number of offspring. 
Women instead tend to be “safer bets”: most women will reproduce, and the difference between the winners and the losers is much smaller.

This has very important consequences:

Men Are More Aggressive Because They Must: Win Big Or Lose It All

The greater fitness variance is the reason why men are more aggressive, competitive, and violent than women.
Men must compete, or they are left out of the mating game. Women’s ability to compete is much smaller, and the dangers are higher.

Women Invest More On Offspring Because Each Offspring Is More Valuable to Women Than to Men

Remember that women invest more in sex cell production and in internal gestation (i.e., pregnancy).
They also invest far more than men once the baby is born.

And remember that men have the potential for far greater reproductive success, even while the woman is still “busy” with that one baby.

That means that each child represents a much greater portion of a woman’s lifetime reproductive potential.
And that’s why women ultimately “care” more about children and willingly invest more.

Why Men Prefer Blonde Bombshells (& Women Want to Be One)

Men prefer blonde women because:

  • Hair tends to become darker with age, so pale color signals youth and fertility

The authors say:

There is nothing arbitrary about the image of ideal female beauty.
These are youth, long hair, small waist, large breasts, blonde hair, and blue eyes. There is evolutionary logic behind each one.

However, I failed to see any more reasons why blonde and blue eyes are “better” than a brunette.

He Said, She Said: Why Do Men and Women Perceive the Same Situation Differently?

Men have more to lose from a false negative -thinking she’s not interested when she actually was-, than from a false positive -thinking she’s interested when she actually wasn’t-.

This only applies to other women, and men tend to assess the interest of their sisters in other men more accurately.

In contrast, women tend to underestimate a man’s romantic commitment to them because the cost of a false positive -thinking that a man is more committed than he really is- is far greater than the cost of a false negative -thinking that he is not romantically committed when he actually is-.

Interestingly enough, the same logic applies in groups.
People tend to be more cautious about free-riding in a group when they are very dependent on that group.

Why Does Having Sons Reduce the Likelihood of Divorce?

A son’s value is largely determined by his wealth.

So by staying within the household, the father can help the child accruing more wealth through fathering, education, direct transfer, and inheritance.

Daughters don’t benefit nearly as much from wealth (or from a father figure), so the father has much less to gain by sticking around (and the mother has much less to gain to keep him around, as well).

Why Are Diamonds a Girl’s Best Friend?

Diamonds help women screen for men who present attractive qualities to start a family:

  • Resources
  • The willingness to spend those resources

Ironically, the more useless the gift is, the more it shows that he is willing to spend and invest.
Diamonds don’t do anything, they are useless. But they show strong financial firepower, and the willingness to dote. 

Why Might Handsome Men Make Bad Husbands?

Men can maximize their reproductive success with two different strategies:

  • Dad strategy: stick with one mate and invest
  • Cad strategy: seek many partners without sticking and without investing (much)

Non-handsome men don’t have the card option (albeit I don’t fully agree here).
Very handsome men do have that option, but that doesn’t necessarily mean they will date as cads.
They might instead still prefer being fathers and “settling down”. But since they have both options, you never know.

More attractive men do indeed have more sexual partners and more extra-pair sex.
And one study shows that handsome men invest less, are less attentive to their partners, and lie more (my note: I wouldn’t trust the “lie” part too much, though).
Instead, more attractive women have more long-term mates than short-term ones.

Also read:

Lover VS Provider: How to Pick Your Best Strategy

Why Rich Men Have More Sons

By now you should know why.

Wealthy and high-status men are more likely to find plenty of mates, so it would make sense for rich and high-status men to have more sons than daughters.
And albeit it might seem like theoretically one cannot choose the sex of their children, there is much evidence to support the Trivers-Willard hypothesis that parents do indeed skew their children’s sex ratio in ways consistent with evolutionary psychology.

Tall and big parents as much as violent people are also more likely to produce boys, while small parents are more likely to produce females.

It’s also been shown that engineers have more sons (140 boys for 100 girls) while nurses have more daughters (140 daughters for 100 sons).
This might be because of the different “brain types” that work well in mathematical professions VS people and “empathy-based” professions.

Why Beautiful People Have More Daughters

Beauty serves both men and women well.

However, it’s more useful for women since women are mostly judged by age and beauty while men are also heavily judged by income, status, and personality as well.

When it comes to long-term relationships, where most children are produced, women do well for short-term and long-term mating, while beauty for men is more useful in short-term mating.

That’s why beautiful people tend to have more daughters.
And the numbers check: young Americans rated as “very attractive” have a 56% chance of having daughters as their firstborn.

Why Are There So Many Deadbeat Dads but So Few Deadbeat Moms?

There are two biological reasons that make fathers worse parents than mothers:

  1. Paternity uncertainty
  2. Higher fitness ceiling (ie.: every single child is more valuable to moms than to dads)

And, ironically, it’s the mother’s higher commitment that allows men to neglect children even more.

Why Old and Young Women Are Most Likely to Kill Children

Young mothers kill their children because they have plenty of time to make more and focus on higher-fitness children.

Older mothers kill their children because they possibly have more children and want to focus their attention and resources on the higher-fitness ones.

Why Do Girls of Divorced Parents Experience Puberty Earlier?

There are two competing theories:

  1. They’re genetically more like their fathers and his “short-term” strategy
  2. They interpret the father’s desertion as a sign that men are not to be trusted and prefer a short-term strategy

Both matter.
Women in polygynous societies hit puberty earlier to get into the high-competition market.
As a sign that the West is moving away from monogamy, the average age of puberty has dropped precipitously in the United States.

Why Are Men More Violent Than Women?

Anne Campbell’s “staying alive theory” suggests that women are more important for the survival of the children.

Thus, it makes sense for women to be less risk-oriented than men.
When women must compete with males, they usually do it in more indirect ways, which also happen to be lower risk.

On the other hand, since men have often played in a “winner takes it all” sexual marketplace, it made sense for them to take more risks.

Why Do Some Men Beat Up Their Wives and Girlfriends?

It’s a maladaptive by-product of “mate guarding”.

And that’s why men guard and beat their wives more when they’re younger and fertile.
Indeed, it’s the age of the wife that predicts male beating, and not the age of the man.

It’s not a Midlife Crisis, It’s Her Menopause

The male midlife crisis is a myth.

In truth, men go on a shopping spree for cool and expensive cars because their wives are approaching menopause, and they prepare themselves to attract younger women.

My Note:
It was very interesting; however, it lacked some strong data to back it up.

Why Men Earn More Than Women

Men earn more because they have to.

Men need those resources to trade them in the sexual marketplace and attract a mate.
And that’s why men are much more stubbornly devoted to making money and achieving higher status.

And, as the authors say:

Women make less money because they have better things to do than make money.

Why Are Most Suicide Bombers Muslims?

Because Islam is openly polygynous.

Polygyny leaves a lot of men without a mate, which in turn makes men more desperate to scramble and risk their lives.

Across all societies, polygyny increases violent crimes.
Then, entered Islam, promising 72 virgins for martyrs.
And the bomber is served. 

The prospect of exclusive access to seventy-two virgins in heaven may not be so appealing to anyone who has even one mate on earth, which strict monogamy guarantees.
However, the prospect is quite appealing to anyone who faces a bleak reality on earth

Male Brain VS Female Brain

The “type S” brain is better at systems, and it’s more common in males.

The “Type E” brain is better at empathizing and is more common in females.

Civilization Only Exists Because of Female Choosiness

Imagine a world where women weren’t sexually selective.

A world where women would have sex with any guy who asked for it.
What would happen in that society?
This is what Miller and Kanazawa say would happen:

Absolutely nothing, because people would never stop having sex!
There would be no civilization in such a society, because people would not do anything besides have sex.

That was a big eureka moment for me.

The open questions of evolutionary psychology

The authors end the book reviewing the open questions from “The Moral Animal“, the book that got them into evolutionary psychology (and the same book that got me into it, BTW).

The questions were:

  • How can evolutionary psychology explain homosexuality?

No good answer is yet available.

  • Why are siblings so different from one another?

Siblings occupy different “niches”.
The firstborn tends to identify with the parents. The latter ones cannot easily take that role and tend to rebel.

  • Why do soldiers die for their country?

Many soldiers are from lower socio-economical classes. 
If they have children already, having the government take care of them in case of death is not too bad.

  • Why some people decide to have few or no kids
  • Why some people commit suicide

Still no answer.
But I’ll provide an answer here.
The mistake, in my opinion, is in the approach that evolutionary psychology must explain everything with a neat theory.
And that’s the consequence of a deterministic view of evolution like everything must happen for a reason and fit neatly like a game of Tetris.

But the world is complex, and evolution is far from perfect.
Evolutionary psychology is big-picture thinking, it should not be able, nor try, to explain the exceptions to the rule.

More Wisdom

  • “Cultures” are different at a superficial level, but deep down they’re the same. And “culture” is just another universal 
  • Humans are naturally polygynous, so almost all societies present a certain degree of polygyny 
  • Contrary to what most people would think, most women benefit from polygyny, while most men benefit from monogamy
  • Polyandrous societies are very rare, and almost all of those few practice “fraternal polyandry”, such as brothers married to the same woman
  • The most successful type of polygyny is sororal polygyny, with sisters married to the same man
  • Girls in polygynous societies are shorter than girls in monogamous societies because there is a race to mature early and become the junior wife of a local high-status man (and girls who mature earlier tend to be smaller)
  • Societies with a high degree of resource inequality lead to polygyny, while well-spread resources can support monogamy
  • Religion is a product of our false-positive bias, and women are more religious because they are more risk-averse (risk aversion correlates with religious beliefs)


Why Beautiful People Have More Daughters has a lot of genius content.
But also some bits and pieces that left me scratching my head, including:

  • Exaggerates the instances of cuckoldry

The authors often repeat estimates of 13–20% rates of cuckoldry in the US (i.e., the husband has no idea he is raising someone else’s child).
I have read very different estimates, and most were lower.

Indeed, the authors themselves later say “although a comprehensive recent review suggests that the actual incidence among Western populations may be much lower, at around 4%”.

But they still seem to relish repeating the much higher statistics, for example:

Mommy’s baby, Daddy’s maybe. And for 10–30 percent of daddies, it is not.

  • Probably wrong analysis of rape (“mate deprivation hypothesis” is incorrect)

The author says that rapists are predominantly from the lower class.
That might be the case for convicted rapists.
However, David Buss, summarizing the latest findings, says that the “mate deprivation hypothesis” is most likely wrong.
Instead, studies also show that men with a high partner count, men of high status, and men who expected to earn a high income were more likely to use force.

  • Sometimes unscientific

The author says that a child represents 1/20 of a woman’s lifetime reproductive potential and 1/1000 of a man’s.
But if we evolved from tribes of less than 150 people, that’s vastly overestimating the man’s realistic lifetime reproductive possibilities.

Also, the authors sometimes confuse correlation with causation, when for example they say that married men produce less because they are enjoying the fruit of their labor (i.e..: a mate).

  • Sometimes on an unscientific political crusade

Sometimes you get the feeling the authors are more focused on a war against politicized sciences than on actually doing science.
However, they sometimes don’t realize they are themselves becoming political just by opposing and questioning the “other side” so strongly.

  • Sometimes it just makes no sense

The authors write:

Men’s status and mate value, unlike women’s, are socially and culturally specific, and they cannot successfully attract women outside of their own society and culture.

This is just plain and untrue.
As a matter of fact, the opposite might be true, and “foreigners” and “outsiders” might get a boost.
Also see: 

Sexual Market Value Hacks: Boosting Your SMV
  • The human penis as a “semen displacement device”

This is most likely not true.
The semen war is mostly fought with testes, not penises.

  • Sometimes sounds conservative and climate-change denialist

The authors write:

Environmental protection is a luxury that became possible to Western societies only in the last several decades.
Before industrialization and the current age of material abundance, all human groups had to exploit the environment to the maximum just to survive.
No one could afford to be environmentally conscious, and Native Americans were no exception.

That’s true, but also rather misleading.
Even if older tribes were environmentally unconscious, which they were, their footprint was still incredibly smaller than our current civilizations.

  • Sometimes lacks a “first-hand” understanding of women

The authors say:

So it makes perfect sense for women to avoid casual sex with anonymous strangers


Women avoid pornography for the same reason that men consume it; in both cases, their brains cannot really distinguish between real sex partners and the imaginary ones.

Alright, for sure, men want more sex with strangers and consume more pornography.
But saying that women “avoid” pornography is, sorry to say, dumb. I have dated more than one woman who watched porn.

  • Random application of evolutionary principles: authors fooled by randomness

The authors commit typical, beginner-level mistakes in their approach to science.
They see a correlation and jump to a conclusion.

Sometimes it doesn’t even make sense. 
For example, they write:

The same logic is probably behind the stereotype that women with large breasts are dumb. In the ancestral environment, without plastic surgery or even bras, only very young women had large, firm breasts.

To begin with, that’s so incredibly random of an explanation.
Second, the breasts often grow with age, and very young women rarely have the biggest breasts.

  • We’re monogamous because resources are better spread out? NO!

The authors write:

The reason most Western industrial societies are monogamous, despite the fact that humans are naturally polygynous, is that men in such societies tend to be more or less equal in their resources, compared to their ancestors in medieval times.

That’s not true.
As other evolutionary biologists have noted the difference between the richest men in Western societies and those at the bottom is much larger than in hunter-gatherer societies.
Maybe what the authors wanted to say is that even men around the bottom of society can (often) feed children.

  • Deterministic: it misses the randomness of evolution

The authors say that “there is nothing arbitrary about the ideal of beauty because it’s been shaped by millions of years”.

That’s not true, and that’s also a major failure to understand evolutionary psychology and the concept of “runaway sexual selection” (Miller, 2000).
At the center of runaway sexual selection is that it can start on quite arbitrary traits and, sometimes, even go against natural selection.

Evolution is much more random than the authors think, and that’s what they fail to understand.

  • Sometimes cultural-denialist

The authors pay lip service to the idea that “culture” matters, but end up sounding very culture-denialists.

They write:

That all human cultures, however exotic and seemingly different on the surface, are essentially the same.
There are no human cultures that are radically and completely different from any other, just like there are no human bodies that are radically and completely different from any other.

The truth is that human nature and culture are not in opposition to each other.
Given a certain culture and environments, different mating strategies and different genes are expressed, leading to very different “human natures”.


However, the true polygynous nature of humans is never too far beneath the surface, even in nominally monogamous societies such as ours.

On childcare after divorce:

Divorced parents with children are playing a game of chicken, and it is usually the mother who swerves

On men working to impress women:

Men have built (and destroyed) civilizations in order to impress women so that they might say yes.

On female power:

For a man to walk into a bar and have his choice of any woman he wants, he would have to be the ruler of the world.
For a woman to have the same power over men, she’d have to do her hair.” 

On racism and education:

Contrary to what social scientists and hippies alike proclaim, we don’t learn to be a racist through parental socialization; we learn not to be one.


I love evolutionary psychology.
And I loved “Why Beautiful People Have More Daughters“. So much so, that I was tempted to give it 5 stars.

It’s a good introductory evolutionary psychology text for the layperson: it gives you a quick overview, in an entertaining format 

In the end, I settled for 4 stars for a simple reason: it’s too politically motivated and too “extremist” in its denial of cultural relevance.

Furthermore, I missed a truly scientific approach.
Correlation was sometimes confused with causation.
And I wished the authors had been more forthcoming in labeling what’s speculation, what’s a theory, and what’s thoroughly backed by data and research.

When an author fails to do so with the most controversial theories, he naturally raises readers’ suspicions.
That’s my second biggest gripe with this book: it should have been more careful and more forthcoming in highlighting the divide between science, speculation, and personal conjectures. 

So, overall judgment?
I loved it and learned a lot, so do read it.
Just make sure you take into account the criticism I listed above.

Also read:

Best Evolutionary Psychology Books

Or get the book on Amazon

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