The Science of Large Breasts, and Other Evolutionary Verities

I blogged nearly a year ago about a study by the evolutionary psychologist Satoshi Kanazawa which argued that beautiful women sometimes marry unattractive men because of the following supply/demand gap: there are simply more good-looking women than there are good-looking men. One reason, Kanazawa said, is that beauty is a more valuable trait for a female, and is therefore accentuated in females via natural selection. Kanazawa and Alan Miller have now co-authored a book called Why Beautiful People Have More Daughters: From Dating, Shopping, and Praying to Going to War and Becoming a Billionaire — Two Evolutionary Psychologists Explain Why We Do What We Do, to be published in September.

First of all, whoo!, long subtitle.

Second of all, there is a sizable excerpt of the book in the current Psychology Today, which includes ten bite-size “politically incorrect truths about human nature” that make the book sound like a blend of Why Do Men Have Nipples, Survival of the Sickest, and maybe … Mad magazine?

Here are the ten topics:

1. Men like blond bombshells (and women want to look like them);

2. Humans are naturally polygamous;

3. Most women benefit from polygyny, while most men benefit from monogamy;

4. Most suicide bombers are Muslim;

5. Having sons reduces the likelihood of divorce;

6. Beautiful people have more daughters;

7. What Bill Gates and Paul McCartney have in common with criminals;

8. The midlife crisis is a myth-sort of;

9. It’s natural for politicians to risk everything for an affair (but only if they’re male); and

10. Men sexually harass women because they are not sexist

In the excerpt, some of the explanations are far more compelling than others. I will chalk this up to the limitations of excerpting. Here, for instance, is Kanazawa and Miller’s explanation of why men like large-breasted women:

Until very recently, it was a mystery to evolutionary psychology why men prefer women with large breasts, since the size of a woman’s breasts has no relationship to her ability to lactate. But Harvard anthropologist Frank Marlowe contends that larger, and hence heavier, breasts sag more conspicuously with age than do smaller breasts. Thus they make it easier for men to judge a woman’s age (and her reproductive value) by sight-suggesting why men find women with large breasts more attractive.

Large breasts as a helpful indicator of age? Really?

I would think that, even during the Stone Age, if a man had to resort to judging a woman’s age by the relative sag of her breasts instead of a number of other signifiers, he probably wasn’t the kind of fellow who was going to successfully reproduce anyway.


#4 - but what defines "femininity"? For the most part it's still evolutionary psychology.

While breast size does not directly correlate with milk production (since breast size is mostly determined by fatty tissue, rather than the size of milk-producing glands), it's not likely our ancestors knew that - female breasts thus developed as a false signal, not unlike the plumage of a peacock, which has no reproductive value either.

#11 - It's because gay men dominate the fashion industry, and their image of "beauty" is that of a young man rather than a young woman. Kind of a weird schism there.

On the article - I agree that sagging breasts as a sign of age is kind of ridiculous, but on the other hand, it's true enough on the other end. Breasts are a sign that a young woman has reached reproductive maturity, and are a reliable indicator of age in that sense.


Response to comment #1: if your hypothesis is that large breasts simply help you identify females better, then you should also explain why no other species have large breasts when not lactating. In particular, our close primate relatives do not have large non-lactating breasts, yet they somehow still figure out who is female.


"but what defines “femininity”?"

I pointed out already, they are those attributes that signal higher levels of estrogen, the female hormone.


#22, I think other species are better able to identify the opposite gender via pheremones. Humans have relatively dull smell senses compared to our animal brethren. Humans have to rely more on visual cues.


I swear that everytime that photo of the breasts scrolls by I first think it's the butt cheeks of some refrigerator repair guy.

Go look for yourself. See what I mean?


Car Tires, Makeup and Darwin.
Ever wondered why men are often more interested in a woman's cup size, her rounded ass and her shapely legs than in her brains? Or why women have often a preference for taller men with broad shoulders and square chins? What makes some Sudanese women believe that using a car tire affixed to their rear part, starting at puberty, in a way that helps growing a bigger butt, is a sine qua non condition to secure a husband later on in their lives? (rest of the post here.


I really wish that people would learn to use qualifiers. It may be that most men prefer blondes with large breasts (although I don't know how true that is), but it certainly isn't true for me. I actually strongly prefer brunettes or redheads with B or C cups, and no more.

Besides that, I see problems with a lot of the statements there. It seems to me that a list like this is more likely trying to get attention than actually being serious. The silly idea that most suicide bombers are Muslim has already been dealt with, and this thread is obviously focused on that first one, but I'd like to point out a huge problem with the ninth statement, that politicians are likely to risk everything for an affair.

I don't really see how he can say that, given that affairs are accepted as normal for most politicians. Occasionally, one will get media attention, but unless there's some especially scandalous details, that won't really do anything to hurt their political career (heck, look at Giuliani, now a major contender for the GOP presidential nomination). An act can hardly be described as not risking everything if it's rarely punished, and even more rarely career-ending.



I read some study a few years ago which argued that the preference for big breasts (not necessarily gigantic, mind you) has to be qualified as "symmetrical big breasts." Nice, big, symmetrical boobs seem to be (and this is what the study found) an evolutionary indicator of a strong and healthy immune system. Of course, we don't have to be conscious of this, but it seems we evolved to prefer nice, round, luscious boobs because they actually are associated with good health, which is always advantageous to pass on to the next generation...


I like the ideas of #s 16 & 24- the connection between larger breasts and pheromone levels... breasts increase in size during menstruation- a period of heightened fertility/arousal...

That, and maybe the freudian "breast milk used to taste delicious"... connecting breast size to ability to produce milk. etc. Just because there's no actual correlation doesn't mean we don't think there is one.


Re #9 - I brought up evolution because the referenced author did.

And yes, this is a rather ridiculous discussion, in general. But I'm generally fine with discussions like that - the more ludicrous, the better, as long as it's still something that can be analyzed rationally. I can have a normal discussion anywhere - weirdness takes some work.


The authors should have pointed out -- especially being evolutionary psychologists -- that primates as a group, and this includes chimpanzees and bonobos, receive sexual stimulation from female buttocks. A female chimpanzee in heat gives a very obvious sign that can be seen from behind when she is on all fours. Now, humans have three features that do away with this sign: 1) we are ready for breeding year-round, 2) we walk upright, putting the buttocks in a less prominent position, and 3) we mate face-to-face (in this we are similar to bonobos, who also prefer face-to-face mating -- we both do this because women have a forward-facing vagina, making such mating more comfortable). However, though we have these three new features, that does not necessarily mean attraction to the buttocks goes away. Humans are the only primates -- the only mammals, in fact -- who retain swolen breasts even when not lactating. Sexual selection for females who retained this fleshy, globe-like feature in plain sight, facing everyone at a more eye-friendly level, would have naturally occured in a species where sexual attraction was focused on fleshy, globe-like, eye-level features. Of course, the larger the breasts, the more buttock-looking they are in appearance. If you do not think this is true, explain why so many comic films and T.V. shows have made use of precisely the visual similarity between butt-cleavage and breast-cleavage? It's funny because it's getting at a deep evolutionary truth about ourselves.



BTW, the flat-chested supermodel thing occurs because the people picking out supermodels 1) are typically gay men, and 2) are looking for moving clothes hangers. The second one is practical, but we can't disregard the first one being a factor, since gay men would naturally find someone with a more triangular body and no breasts more attractive, since they would have a more masculine appearance.


Of course, the larger the breasts, the more buttock-looking they are in appearance.

I told you so. My idea. Please see comment #25. This idea is now copyrighted, by me. And my plumber.


uhh...boobs are cool...huhuh


It's weakly supported stuff like this, reported widely in the popular press, that gives psychology a bad name.

When I entered the field, I thought I was going to do science (even if social science). Then I discovered the stuff people were really interested in was the pop-psychology stuff.

It's not that evolutionary psychology is necessarily buffoonery. It's just that some practitioners seem to emphasize that aspect. [10 exhibits in support of this thesis in Dubner's posting]


Most of the soft sciences like psychology suffer this kind of thing because the evidence has typically been so circumstantial and less certain than results from the hard sciences. Evolutionary psychology has actually moved psychology closer to being a hard science than any other movement in psychology -- it has at least resulted in testable hypotheses. The soft sciences suffer the problems they do because the more complex something is, the harder it is to produce repeatable results. That is why quantum theory is the most proven theory of any sicentific theory, chemical experiments are repeatable, biological experiments less so, most behavioral experiments (especially with organisms that have more complex behaviors) even less so, etc. up to things like psychology and economics, which deal with things so complex it almost doesn't look like science any more, but increasingly like the products of the humanities (which are themselves more complex than psychology and economics -- though we mistakenly think of them as easier).



Fashion-model type physiques are very attractive to at least one straight man.

And from Carolyn Latteier, the author of Breasts, The Women's Perspective on an American Obsession, in a TV program "All about breasts":

"Well, we do have a peculiar obsession with breasts in this culture. A lot of people think it's just the human nature to be fascinated with breasts but in many cultures, breasts aren't sexual at all. I interviewed a young anthropologist working with women in Mali, in a country in Africa where women go around with bare breasts. They're always feeding their babies. And when she told them that in our culture men are fascinated with breasts there was an instant of shock. The women burst out laughing. They laughed so hard, they fell on the floor. They said, "You mean, men act like babies?" Link:

Of course, as noted above, the Tamil Tigers, drawing from a mere 6.5 million Sri Lankan Tamils, had the top suicide-bombing position, at least up to the point just before the Iraq war when "Frontline World" reported on it.

It's a shame the editors at Psychology Today weren't more rigorous in applying Occam's Razor.



We men are triggered by such simple things, its archaic, a remain from the stone age:

Big breasts - feeding
Long legs - Can carry the child run fast, when a mammoth comes :)


Fashion magazines are generally perused by women.

Men tend to peruse mags like Playboy, Maxim, SI Swimsuit, etc.


Don't confuse attraction with fascination. Fascinaiton is caused by the fact that we have fetishized the breasts by insisting they be covered. In cultures where bare breasts are the norm, the fetishization does not occur and there's no obsession with seeeing them. That does not mean, however, that they do not serve an attractive purpose.

Still, there is a point to be made with fetishization. Many cultures have created various sexual fetishes that have augments and sometimes partially replaced what nature has given us. With human behavior, we have to talk about tendencies, not pure absolutes. Genes give us tendencies that can and are affected by cultural differences.