Category Archives: Evolutionary Psychology

Why do we like foods that are bad for us?

How about a pepperoni and sausage pizza with extra cheese? Or perhaps a chocolate eclair?

No thanks, you say? You like those foods, but you’re trying to eat healthy? Well darn — why is it that everything that tastes good is bad for us?

OK, that’s a bit of exaggeration, but we do like fats, sugars, and salt, all to our detriment — they contribute to obesity, diabetes, heart disease, cancer, and more. It seems odd, doesn’t it? Why would we evolve to like foods that are bad for us?

Well hey, I have some great news! The reason we like those things is that they are actually good for us! Really, that’s true — but only if you take it in context.

Our distant ancestors didn’t have supermarkets with candy aisles. Even fruits available to them were hardly sweet at all compared to the fruits we eat today, which are the result of many, many generations of selective breeding for taste. Our ancestors hunted, but during most of our evolutionary history success was by no means assured — they occasionally brought home some meat. And that meat was not marbled with fat like the cows we eat today, which were not only bred for taste but also given cushy lives so that their muscles don’t get tough.

So we evolved over many, many generations during which fats, sugars, and the like were generally not available in quantity. Whatever little bits you were lucky enough to come across, it was to your benefit to eat. Those who liked such foods were more motivated to eat them when available, and they benefited from the nutritional boost, which ultimately translated into greater reproductive success — they really needed the calories. So the genes that programmed into their brains the taste for such foods were passed on with greater success.

To drive this home, picture yourself lost on some grassy plains, with trees here and there. You haven’t eaten much today, so you are motivated to find something. A few of the trees and bushes have fruits that you sort of recognize. You try one and quickly spit it out — bitter. After some experimentation you find one that is, well, not great — nothing like the fruits you are used to eating — but not disagreeable. The chemical laboratories in your tongue and nose steered you away from foods which probably weren’t going to work for your body, toward foods that might. That is what your senses of taste and smell are for, not to help you decide between broccoli and Twinkies. There were no Twinkies.

But that’s why we like sweet foods today: they were a good sign for us health-wise way back then. Our ancestors were the ones who did like sugars and fats; the ones who didn’t fared less well, and their genes became less common. That’s how evolution works. But now we are able to refine and concentrate sugars and fats to form the nutritional monstrosities that call to us like sirens from supermarket shelves, and in those concentrations they are by no means good for us.

If such unhealthy crap had existed in our evolutionary past (imagine giant Twinky trees on the savanna, laden with “fruit”), we would have had to evolve to deal with it.  Our bodies might have evolved to be a little more tolerant of sugar/fat bombs. Our brains might have evolved to enjoy a little bit of Twinky now and then, but to quickly lose interest, preferring foods with the nutrition our bodies need. But that didn’t happen, because there were no Twinky trees until recently. So we are defenseless, led by our senses — like moths to a flame — to obesity, diabetes, and heart disease.

Well, OK, we aren’t quite defenseless — we can, through our intellect and force of will, override our pleasure system. But that works much better for some than for others.

After I explained this to a friend, he asked “but aren’t we evolving to deal with much higher concentrations of sugars, fats, etc.?”

Unfortunately it’s not that simple. To understand why, consider what that evolution would look like. People whose genes build bodies which don’t handle these excesses well would have to be less successful reproducers, so that their genes would become less frequent in the gene pool. A key way such people would be less successful reproducers is by dying. Well, they do die, you complain! Yes they do, BUT — they would have to die soon enough to reduce the number of children they have (and raise successfully). These days we expect to have a couple of kids in our twenties or thirties and live into our eighties. Natural selection doesn’t much care if you die in your fifties of heart disease if you weren’t going to have more kids after that anyway.

To be fair, grandparents can be of some benefit in raising their grandchildren, although that’s probably far less a factor than it used to be, what with insurance and social programs that use tax money to help the needy, not to mention the fact that at least here in the U.S. grandparents don’t typically live with their grandchildren anymore. In fact, it may be that — from our genes’ point of view, which is always about reproductive success — it is better nowadays if grandparents die young and leave a larger inheritance to their descendants sooner!

So no, sorry — we are probably not significantly evolving toward bodies that run just fine on cheeseburgers and ice cream. And in fact that’s almost surely not what would happen even if we were dying soon enough to reduce our reproductive success; incremental changes to our brains that cause us to like sugars and fats less are far more likely than sweeping changes to our physiology to allow us to thrive on junk food.

Human beings are intelligent planners, capable of working out the means to attain goals. But an old part of your brain tries to “steer” you and your great planning ability toward reproductive success by dumping neurotransmitters into your noggin to control how you feel. And there is something you should know about that old part of your brain, this part that controls what you like: it’s dumb as a stone. Worse, it has no idea that the industrial revolution happened.

Think of this old part of your brain as the firmware in a computer. I call this part of my brain Dumbo, and the corresponding part of a woman’s brain Morona. Dumbo and Morona only get updated by evolution, a glacially slow process that — as we saw above — doesn’t necessarily lead us someplace we’d like to go, because humans want more out of life than just lots of descendants. Dumbo and Morona do not reason; they execute encoded heuristics that contribute to reproductive success. The encoding that is there is almost entirely from a time when our lives were not very much like they are today, so there is a huge gap between the environment we were programmed to live in and the one we really do live in. Dumbo thinks I am a hunter-gatherer, and that if I run across a bit of sugar or fat it’s an opportunity not to be missed. So that’s how he steers me.

Quite a lot of human unhappiness is the result of Dumbo and Morona being in serious need of an update; stay tuned for more about that.

But for now, hand me another slice of that pizza, would you?

For those especially interested in evolution…

I should be honest here and say that there are other ways (besides dying early) in which evolution could operate on our desire to eat foods that are bad for us, but they don’t change the story. I’ll go through a couple of those here.

1. You could become undesirable during mate selection and have trouble finding a mate. This kind of selection is called “sexual selection.” So if a person’s genes contribute to their eating a diet which makes them less desirable as a mate, then they will have fewer choices in the mating game.

2. You could have trouble performing the tasks required to raise a family. So if a person’s genes contribute to their eating a diet which makes them sick (diabetes leaps to mind), that could theoretically impact their reproductive success.

Eons ago, these would have been very important factors — had junk foods been available. Couples didn’t use birth control to limit themselves to a couple of kids; dying early might very well reduce the number of children you left behind. Getting a disease like diabetes was much more likely to kill you or leave you incapacitated and unable to take care of your family. Modern medicine (and the insurance that pays for it) can inform us of the danger of such a diet and significantly ameliorate its effects. For example, a diabetic might be given insulin — paid for by insurance — and still work and raise a family.

Long ago, a less desirable mate might have meant less children — after all, what we find attractive in a mate is largely about reproductive potential (more on this in later posts!). But modern medicine goes a long way toward allowing everyone who wants a child to have one — even if, for example, they don’t have optimal hormone levels or hips wide enough for a safe delivery. A graduated income tax and other “progressive” policies go a long way toward allowing everyone who has a child to raise it successfully. And birth control drastically reduces the number of children we have from our true reproductive potential. And frankly, a lot of those heuristics are horribly out of date anyway. So really, not getting as attractive a mate has little effect on reproductive success these days.

Eons ago, you couldn’t eat junk food — it didn’t exist. Now that it does, the effects on reproductive success are pretty limited, so evolution doesn’t have a lot to work with.

Impostor Syndrome

You may have heard of the Impostor Phenomenon (sometimes called “Impostor Syndrome“), the feeling that the success and praise you are getting is undeserved, that you were just lucky. You feel like a phony. It was once believed to be particularly common in successful women, but apparently men suffer from it commensurately; I suspect that men simply don’t report the feeling as frequently, being 1) less inclined to share this or any other feeling, and 2) more motivated to appear invulnerable — no cracks in the armor.

This article quotes one researcher as saying that some people are “phony phonies,” feigning modesty for their own benefit:

“Particularly when people think that they might not be able to live up to others’ views of them, they may maintain that they are not as good as other people think,” Dr. Mark Leary, the lead author, wrote in an e-mail message. “In this way, they lower others’ expectations — and get credit for being humble.”

I think that’s something our culture encourages, and is likely even wired into us. We like the successful person who doesn’t flaunt it, the astounding teammate who treats us all as equals, the beautiful woman who doesn’t seem to realize she is beautiful. We award others bonus points if they appear to underrate themselves.

It’s not hard to suggest an evolutionary basis for this bias: these people’s services appear to be on sale. In seeking an alliance or a mate or any other exchange, you would have fared better with those who genuinely undervalued themselves than with those who thought they were hot stuff. Genes causing a preference for such “deals” might well have had greater reproductive success, causing the preference to spread throughout the population. In fact, the genes wouldn’t even have to be specific to modesty; brain circuitry for recognizing a deal in any context would probably suffice.

Given such a preference for modesty encoded into our brains (or at least a preference for bargains and the ability to recognize modesty as a sign of one), that would in turn create evolutionary pressure to feign modesty, because it makes you more attractive (which of course contributes to reproductive success).

But OK, enough of phony phonies — there are plenty of folks who really do feel like phonies. I remember the feeling quite distinctly growing up, and am aware of some contributing factors. For example, my father was fascinated by telekinesis, and he described it to me one day when I was perhaps eight years old. “As smart as you are,” he said encouragingly, “you should be able to do this.” He urged me to practice moving objects with mind power.

So I did. Practice, that is — not move objects. For years, off and on, I tried to move pencils, spoons, and the like, experimenting with various ways of trying to compel them. Nothing ever worked, not even a little bit. “As smart as you are, you should be able to do this,” he had said. The conclusion was obvious: I wasn’t really that smart. That’s why the spoon was not moving.

I’m sure my father didn’t deliberately set me up to fail, or to link that inevitable failure to a lack of intelligence. He no doubt believed that telekinesis was possible and that if you could convince a young child that s/he could do it, they might just succeed. And wouldn’t that be cool! But the result was abject failure, and a resulting deep suspicion that the intelligence others thought they saw in me was illusory. I could not even move a spoon with my mind.

And there are other ways to elicit this feeling of being an impostor. For example, “intelligence” is a broad term that encompasses multiple traits, but we talk about it as if it were a single characteristic. If a child has a generous helping of all of the underlying traits, then sure, we say the child is intelligent. But what if a child has, say, strong analytical skills and good semantic memory, but poor episodic memory? The child will excel in many academic ventures and be called intelligent, but will struggle and often fail at commonplace tasks that most people can handle. “Aw, Billy — you can’t remember that? What’s the matter with you — you are supposed to be so smart!” Such children, not understanding that there are various aspects to what we call intelligence and that they possess more of some than others, can easily feel like phonies.

Or what if an otherwise bright child has a relatively limited short-term memory? Academic exercises, which are typically distilled to just the relevant facts for pedagogical reasons, will likely seem easy, but messy real-world situations will be harder to keep track of. Again, a parent’s reaction can be devastating, but so can that of peers. Classmates who might resent curve-breakers held up as examples by the teacher are sometimes eager to tear them down when they make a mistake. Monday yields an award, Tuesday a humiliation.

And of course, even academically gifted kids do stupid things. “When are you going to get Brain One?!” my father would often shout when angry.  He never told us what Brain One was, but the implication was obvious. So what’s the truth here — those awards for academic achievement in school, or these angry assessments?

There are probably lots of other ways to induce the same confusion and lack of confidence, all leading to roughly the same place. While receiving an award for academic performance, a child might secretly remember repeatedly feeling like a fool at times when his memory failed him. Simultaneously the child feels pride in the accomplishment and worry that this is all a mistake, that s/he will not be able to live up to expectations and will be exposed as a fraud.

If the child lacks self-esteem and feels unloved, the problem is exacerbated. If a child only feels appreciated for his or her intelligence, then the fear of being a phony can be quite acute.

And of course the same thing can happen with adults. You might be good at certain types of things, and really not so good at others, and not be clear on the difference. To you it just seems that sometimes you shine, and sometimes you stink. Who wouldn’t feel like an impostor, especially if you didn’t have good self-esteem to start with?

And finally, luck really does play a part in success. So do other non-meritorious factors like money, looks, connections, and outright cheating. Some portion of that feeling of being a phony may, for some people, actually be quite well-deserved.

A hypothesis about our preference for tall leaders

Researchers have long known that humans generally prefer (all else being equal) taller leaders. Taller people are more likely to be elected to office, become CEO, get paid more, be considered more authoritative, etc. But why would that be? It seems kind of silly — what does height have to do with ability to lead?

Since this is widespread it likely has some genetic basis, but what in the world would be adaptive about being biased toward following the taller of those who try to lead? Unless there really were a correlation between height and ability to lead, then such an innate preference would just weaken our ability to choose good leaders, causing us to discount whatever truly useful data we had about the person’s intelligence, temperament, skills of persuasion, etc. There must be some context in which an inclination to follow the lead of tall people makes good sense, or the genetic basis for it would have been extinguished.

A possible answer hit me today. Of course, in order to talk about an evolutionary explanation for anything, we must imagine humans hundreds of thousands of years ago, in conditions very different from those of modern life. So yes, imagine yourself way back when — still, why prefer what the tall guy suggests? What sense would that make?

Probably none if you are an adult. But if you are a five-year-old kid playing with other kids in your clan, and something out of the ordinary happens, then you would probably do quite well to follow the lead of the older kids in the group. They know the most about the environment. They have absorbed the most wisdom from their parents. They likely have the best impulse control and sense of responsibility to the group.

And of course those older kids are very likely the tallest kids. Genes seldom travelled long distances in those days, so genes for height would have been pretty similar within a clan. So height among kids was surely an excellent proxy for age (better even than it is today), and hence for wisdom. So, perhaps kids with a built-in heuristic that told them to follow the lead of the tall survived to reproduce a little better than those without it, passing the genes responsible for the preference on to us.  The fact that adults exhibit the bias could just be a side effect. Since people did not live as long back then, there would have been less downside to being influenced by irrelevant factors as an adult.

Or hmmm, perhaps the fact that the group agreed on a leader was generally more important than that you chose the best one — the group had to stick together rather than splinter over leadership. In that case height, while being completely uncorrelated with adult leadership skills, serves as an unambiguous criterion by which social cohesion is enhanced: we agree on Fred as our leader because he is the tallest. Being tallest is really only intrinsically relevant to leadership when we are children, but as adults we need some way to choose between otherwise-equal candidates, and what the hell — height will serve.

I have no idea how we could test this hypothesis….


A recent study suggests that we consider men with beards more authoritative, too. These days lots of grown men don’t have beards, but back then if you were an adult male, you generally had a beard, so this seems like another case of an age indicator conveying authority.

[Note: I’m skeptical about the study’s attempt to say anything about the attractiveness of bearded males, since they specifically used expressions of anger.]

Why (many) men like large breasts

This is one of my most visited posts, so I wanted to make it a little easier to tell what it is suggesting. Toward that end I created this infographic:

[now the original post]

Hmmm. I just read the following in an interesting article in Psychology Today about evolutionary psychology, one of my favorite topics:

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.

It isn’t clear to me why finding large breasts attractive isn’t a simple case of a supernormal stimulus at work.

Putting that aside, I can see the point. Ultimately what we find attractive in a potential mate are those features which, in the environment in which we evolved, tended to lead to having lots of progeny. Our entire notion of what is sexually attractive is encoded into our brains today for the very reason that those who had it over the millennia left more copies of their genes behind.  Many thousands of years ago, people didn’t live to a ripe old age, so you needed to have kids while the iron was hot, so to speak; you were probably going to be dead at 30 and making babies until it happened. Hence mechanisms in the male brain that made him better at choosing a younger (but still fertile) woman as his primary partner were generally adaptive, because they left more time for baby-making.

On the other hand, they were only adaptive to the extent that you couldn’t already tell a woman’s age — was that a problem? Faces and voices and skin tone and energy level and behavior and peers and so on seem like pretty good indicators too. After all, most women wear bras these days (among many other mechanisms to give the appearance of youth), but we can still generally tell the difference between a 15-year-old, a 20-year-old, and a 25-year-old, can’t we?  Would larger but variable breasts on young women really make it easier to judge their age?

Beyond that I have a problem with the quote’s dismissal of a relationship with lactation.

Yes, if we were to measure breast size and lactation today, I doubt that there would be a significant correlation. But that doesn’t mean that there was no such correlation in our ancient past. Imagine women hundreds of thousands of years ago, who almost certainly had much smaller breasts than women today (we are the exception among primates).  Picture that, for whatever reasons, some of these women have breasts that are less developed functionally than others, and these are often smaller. Perhaps they have poorer immune systems and have therefore struggled more with parasites, a major problem in those days. Or maybe these women were malnourished during a critical period. Or their hormone levels weren’t right during development.  Or perhaps their genes for the construction of mammary glands are just off. In any case, among the small breasts of the day, theirs are smaller, for reasons that will negatively impact their children.

In such an environment, genes that gave men a preference for larger breasts would do well because they would tend to result in healthier children. In those days, “larger” meant something else, perhaps still tiny compared to women of today. But genes encoding such a preference into the male brain would cause average female breast size to increase over the millenia, just as the peahen’s preference for males with longer tails with lots of eyes gradually increased tail size in peacocks. Women who tended to accumulate fat in the breasts (a cheap way to make breasts larger) were considered more attractive, even though the fat had nothing to do with fertility. And just as the peahen’s preference persists even now, when peacocks have enormous tails that make them less able to escape predators, the human male’s preference for larger breasts would persist even though it no longer really means that his children will be better fed or have a better immune system.

In other words, just because you can’t tell anything about how much milk a 600cc breast will produce vs. a 300cc breast — the difference generally being the amount of fat in the breast — that doesn’t mean that preferring a 60cc breast over a 30cc breast wouldn’t have been adaptive way back then. The inflation to today’s numbers could just be a long-term effect of the preference itself, the result of generation after generation of men preferentially selecting women who tended to accumulate fat in the breasts. This kind of effect (if that’s really what’s going on here) is called a Fisherian runaway, after the genius who first suggested it.

In other words, just as women with small breasts today may use padding to trick the male brain into being more attracted to them, women’s DNA may have evolved to pad their breasts on the inside for the same reason.

By the way, you might think that a mutation that eliminated peahens’ preference for long tails with lots of eyes would do quite well, since the resulting males, which would tend to have shorter tails, wouldn’t be so handicapped against predators. But in fact those males would have trouble attracting a mate, so the mutated gene would die out.

If there are in fact genes that cause a preference for larger breasts, then where does it stop? Why not breasts the size of a house? Well, for one thing there are health implications beyond a certain point.  But we also seem to have a preference for “normal” — that is, we find anything too far out of the ordinary unattractive. A guy might be attracted to somewhat larger breasts than normal, but he is not attracted to breasts that are so enormous compared to what he has seen before that they seem freakish. Full lips (a sign of female hormones) are also generally considered attractive, but not so full as to seem abnormal.

But today, it is possible and even common for women to simply buy larger breasts (roughly 5% of American women have breast implants now, and if recent trends continue that number will double in the decades to come), or to buy devices that make their breasts look larger, in an effort to make themselves more attractive — ultimately to the genes that construct the male brain. As more and more women do this, it raises the standard for “normal,” and still larger breasts then seem attractive.  Then women want larger implants, and so on.

On the computer, of course, it is simply a matter of moving pixels around, and the laws of physics are no obstacle in cyberspace. Images abound on the web of women with breasts that, for most of us, seem ridiculously large. No doubt there is some variation among males in the strength of their preference for large breasts. But it is also true that on the web men can repeatedly find images of women with breasts a little larger than what they are used to seeing, and in so doing continually ratchet up their idea of what is “normal.” Breasts that seem abnormally large or round to one man may be attractive to another man simply because the latter is used to seeing breasts like that — to him, they no longer seem abnormal.

So — couldn’t that be a reasonable hypothesis for why many men have a preference for larger-than-average breasts? In fact, we are generally attracted to somewhat exaggerated sex organs and secondary sex characteristics because they imply good levels of sex hormones. This makes us responsive to supernormal stimuli.

[I’d love to hear from a professional in the field of evolutionary psychology on these thoughts. I am *not* one.]