Sex with a stranger? Evolutionary psychology and sex differences in behavior

June 6, 2021 • 9:15 am

In the early days of evolutionary psychology—that is, when it was just beginning to be applied to humans—I was rather critical of the endeavor, though not so much about “sociobiology”, the application of evolutionary principles to animal behavior. A lot of the early evo psych stuff on humans was weak or overly speculative.

Since then, I’ve mellowed somewhat in light of replicated research findings about human behavior that show phenomena predicted by or very consistent with the theory of evolution. Not only are the phenomena predicted and replicated, but they are in line with what other animals show. Further, researchers have also falsified some alternative explanations (“culture” or “patriarchy” is the most common one).

I’ll add here that the disturbingly common claim that evolutionary psychology is “bogus” or “worthless” as an entire field is ridiculous, both in principle and in practice. In principle, why should human behavior, or behavioral differences between the sexes, be the one area that is exempt from evolutionary influence, especially given that we evolved in small hunger-gatherer groups for at least five million years, on top of which is overlaid a thin veneer (about 20,000 years) of modern culture? That position—that all differences between men and women, say, are due to cultural influence—is an ideological and not an empirical view. If physical differences, both between sexes and among groups, are the result of evolution, why not mental ones? After all, our brain is made of cells just like our bodies!

In practice, there are several types of human behavior that, using my mental Bayes assessment, I consider likely to reflect at least some of the workings of evolution, past and present, although culture may play a role as well. There will be an upcoming paper on these fairly solid evo-psych behaviors (I’m not an author), but I’ll highlight it when it’s published.

In the meantime, we have one behavior, described in this 2017 article from Areo Magazine, that describes a “universal human behavior” involving sex differences, and a behavior that’s likely to reflect our evolutionary heritage. Although the article is four years old, it’s worth reading. The author, David P. Schmitt, has these bona fides:

David P. Schmitt, PhD, is Founding Director of the International Sexuality Description Project, a cross-cultural research collaboration involving 100s of psychologists from around the world who seek to understand how culture, personality, and gender combine to influence sexual attitudes and behaviors.

See also his Wikipedia page, which describes him as “a personality psychologist who founded the International Sexuality Description Project (ISDP). The ISDP is the largest-ever cross-cultural research study on sex and personality.”

The article, which I recommend you read, is chock-full of data. Click on the screenshot for a free read:


The behaviors Schmitt discusses in this longish but fascinating and readable piece are summarized in the first two paragraphs (there are lots of references should you want to check his claims):

Choosing to have sex with a total stranger is not something everyone would do. It probably takes a certain type of person. Quite a bit of evidence suggests, at least when it comes to eagerly having sex with strangers, it might also take being a man. Let’s look at the evidence.

Over the last few decades almost all research studies have found that men are much more eager for casual sex than women are (Oliver & Hyde, 1993; Petersen & Hyde, 2010). This is especially true when it comes to desires for short-term mating with many different sexual partners (Schmitt et al., 2003), and is even more true for wanting to have sex with complete and total strangers (Tappé et al., 2013).

Of course this is “common wisdom” in American culture: it is the heterosexual guy who does the pursuing, and does so without many criteria beyond the lust object having two X chromosomes, and he’s still often rejected, while women are far choosier about who they mate with.

There are many studies, described and cited by Schmitt (usually using lab experiments or good-looking students on campus approaching members of the opposite sex) that show the same thing. An attractive man propositioning a woman for sex is accepted about 0% of the time, while, in the opposite situation far more than half the males accept a sexual proposition from an attractive female stranger. Here are two studies, but there are more:

In a classic social psychological experiment from the 1980s, Clark and Hatfield (1989) put the idea of there being sex differences in consenting to sex with strangers to a real life test. They had experimental confederates approach college students across various campuses and ask “I’ve been noticing you around campus, I find you to be very attractive, would you go to bed with me tonight?” Around 75 percent of men agreed to have sex with a complete stranger, whereas no women (0 percent) agreed to sex with a complete stranger. In terms of effect size, this is one of the largest sex differences ever discovered in psychological science (Hyde, 2005).

Twenty years later, Hald and Høgh-Olesen (2010) largely replicated these findings in Denmark, with 59 percent of single men and 0 percent of single women agreeing to a stranger’s proposition, “Would you go to bed with me?” Interestingly, they also asked participants who were already in relationships, finding 18 percent of men and 4 percent of women currently in a relationship responded positively to the request.

This of course jibes with the behavior of many animals (in my flies, for example, males will court almost any female, even wooing pieces of dust or small blobs of wax), while females repeatedly reject males. It’s true of primates in general, and of many animal species. And it makes evolutionary sense. If a male mates with five females instead of one, he’s likely to have five times more offspring. In the reverse situation, though, a female who mates with five males in a short period will have roughly the same number of offspring as if she mated just once. That’s because she makes a huge investment in eggs and (in some species like ducks) maternal care, and so she should be selected to be choosy about her mates, looking for a male who is fit, healthy, may have good genes, and, if there’s parental care, will be an attentive father. Since the male has far less to lose, and far more to gain, by repeatedly mating with different females, this explains the strategy of “wanton male versus choosy female” sexual preference. These are likely to be evolved sexual behaviors.

This of course is a generalization. There are certainly picky men and women who are less choosy about their partners. But it’s a generalization that holds up not only in the “choice” studies I just mentioned, but in other aspects as well. Psychological studies show that (here I quote Schmitt, bolding is his)

. . . men have more positive attitudes towards casual sex than women, have more unrestricted sociosexuality than women, and generally relax their preferences in short-term mating contexts (whereas women increase selectivity, especially for sexual attractiveness.

. . . Cognitively and emotionally, men are more likely than women to have sexual fantasies involving short-term sex and multiple opposite-sex partners, men perceive more sexual interest from strangers than women, and men are less likely than women to regret short-term sex or “hook-ups.”

Considering sexual fantasies, men are much more likely than women to report having imagined sex with more than 1,000 partners in their lifetime (Ellis & Symons, 1990).

Behaviorally, men are more likely than women to be willing to pay for short-term sex with (male or female) prostitutes, men are more likely than women to enjoy sexual magazines and videos containing themes of short-term sex and sex with multiple partners, men are more likely than women to actually engage in extradyadic sex, men are more likely than women to be sexually unfaithful multiple times with different sexual partners, men are more likely than women to seek one-night stands, and men are quicker than women to consent to having sex after a very brief period of time (for citations, see Buss & Schmitt, 2011).

Here’s a table reproduced in the Areo paper taken from Buss and Schmitt (2011), where you can find the original references. Click to enlarge.

These patterns hold in nearly all studies in different parts of the world. That in itself suggests that culture may play an insignificant role in the difference I’m discussing.

Now if you’re thinking hard, you can think of at least four non-evolutionary explanations for these behaviors (I’ve combined disease and pregnancy in #3 below). Both, however, have been shown to be unlikely to be the major explanation for the sex difference in choosiness.

1.) Patriarchy: These could be cultural differences enforced by the patriarchy and socialization. Why a patriarchy exists itself may be evolutionary (e.g., males are stronger and thus can control females more easily than the other way around), but male dominance itself is not the explanation we’re testing here. Schmitt explains why (beyond observed cultural universalism), this is unlikely to explain the entire behavioral difference (all emphases are the author’s):

For instance, Schmitt (2015) found sex differences in the sociosexuality scale item “I can imagine myself being comfortable and enjoying ‘casual’ sex with different partners” were largest in nations with most egalitarian sex role socialization and greatest sociopolitical gender equity (i.e., least patriarchy, such as in Scandinavia). This is exactly the opposite of what we would expect if patriarchy and sex role socialization are the prime culprits behind sex differences in consenting to sex with strangers.

How can this be? Why are these sex differences larger in gender egalitarian Scandinavian nations? According to Sexual Strategies Theory (Buss & Schmitt 1993), among those who pursue a short-term sexual strategy, men are expected to seek larger numbers of partners than women (Schmitt et al., 2003). When women engage in short-term mating, they are expected to be more selective than men, particularly over genetic quality (Thornhill & Gangestad, 2008). As a result, when more egalitarian sex role socialization and greater sociopolitical gender equity “set free” or release men’s and women’s mating psychologies (which gendered freedom tends to do), the specific item “I enjoy casual sex with different partners” taps the release of men’s short-term mating psychology much more than it does women’s. Hence, sex differences on “I enjoy casual sex with different partners” are largest in the most gender egalitarian nations.

Overall, when looking across cultures, reducing patriarchy doesn’t make these and most other psychological sex differences go away, it makes them larger (Schmitt, 2015). So much for blaming patriarchy and sex role socialization.

2.) Fear of injury. In general, men are stronger than women (this is almost surely the result of evolution affecting competition for mates). Perhaps women are leary of accepting propositions from unknown men because they might get hurt, as do many prostitutes. But several studies show that safety alone cannot be the whole explanation:

Clark (1990) was among the first to address the issue of physical safety. He had college-aged confederates call up a personal friend on the phone and say “I have a good friend, whom I have known since childhood, coming to Tallahassee. Joan/John is a warm, sincere, trustworthy, and attractive person. Everybody likes Joan/John. About four months ago Joan/John’s five year relationship with her/his high school sweetheart dissolved. She/he is was quite depressed for several months, but during the least month Joan/John has been going out and having fun again. I promised Joan/John that she/he would have a good time here, because I have a friend who would readily like her/him. You two are just made for each other. Besides she/he has a reputation as being a fantastic lover. Would you be willing to go to bed with her/him?” Again, many more men (50%) than women (5%) were willing to have sex with a personally “vouched for” stranger. When asked, not one of the 95% of women who declined sex reported physical safety concerns were a reason why.

3.) Fear of pregnancy and/or disease. Since venereal diseases can be passed in both directions, I’m not sure that disease is a good explanation, though perhaps women are more likely to get serious disease than are men. As far as pregnancy is concerned, there’s at least one study showing it can’t be the sole factor:

Surbey and Conohan (2000) wondered whether worries of safety, pregnancy, stigma, or disease were what was holding women back from saying yes to sex with a stranger. In a “safe sex” experimental condition, they asked people “If the opportunity presented itself to have sexual intercourse with an anonymous member of the opposite sex who was as physically attractive as yourself but no more so (and who you overheard a friend describe as being a well-liked and trusted individual who would never hurt a fly), do you think that if there was no chance of forming a more durable relationship, and no risk of pregnancy, discovery, or disease, that you would do so?” On a scale of 1 (certainly not) to 4 (certainly would), very large sex differences still persisted with women (about 2.1) being much less likely to agree with a “safe sex” experience with a stranger compared to men (about 2.9).

So, sex differences in agreeing to sex with strangers are not just a matter of safety issues, pregnancy concerns, slut-shaming stigma, or disease avoidance. Controlling for all of that, researchers still find large sex differences in willingness to have sex with a stranger.

There’s a lot more in this paper, including Schmitt’s critique of the two papers cited widely as disproving the “pickiness” hypothesis. Both papers, however, suffer from extreme methodological flaws, and in both cases the results support the “pickiness” hypothesis when the flaws are corrected.

You can read the hypothesis and judge for yourselves, but I think this is one of the best examples we have of evolutionary psychology explaining a difference between men and women in behavior*. As I said, it’s shown up throughout the world in different cultures, it’s paralleled in many species of animals, alternative explanations fail to explain the data, other, unrelated data support at least a partial evolutionary basis of the choice difference, and the few papers that claim to disprove it wind up actually supporting it.

Aside from “universal” behavior like sleeping, eating, or wanting to reproduce, which are surely instilled in us by evolution (and nobody questions those), we shouldn’t ignore differences between groups, especially the sexes, as having an evolutionary origin. It’s likely that morphological differences between geographic populations, like the amount of melanin in the skin, are adaptive responses to natural selection, so why is behavior the one trait that is always off limits to evolutionary explanation?  It’s ideology, Jake.

h/t: Steve Stewart-Williams


*As a reader points out below, and even more obvious evolutionary difference is that the vast majority of men are sexually attracted to women, and vice versa. That would be hard to explain as a result of the patriarchy or of socialization.

58 thoughts on “Sex with a stranger? Evolutionary psychology and sex differences in behavior

  1. You write “at least four” but mention only three.

    Obvious way to disprove the pregnancy angle: women do not become nymphomaniacs after menopause (well, most women don’t).

    To me, the findings are obvious.

    1. As a woman in menopause, let me tell you that my sex drive, sexual phantasies etc went from very high to near zero within 2 years of menopause. My physical ablity to experience vaginal orgasm went down the drain at the same time, as did lubrication. Can’t vouch for others, women have a high variabilty in sex things.

  2. Note also that, at least where prostitution is legal, those few women who are nymphomaniacs often become prostitutes, as there is no way that one man could satisfy them. This is a win-win situation, since they earn more than in other jobs and provide an outlet for all those horny blokes. (That is not to say that most prostitutes are nymphomaniacs. Most are like ordinary working people: they enjoy the job to a greater or lesser extent depending on several factors but probably wouldn’t continue with it if they became suddenly rich. And only a small minority of prostitutes are forced into prostitution, at least where prostitutions is legal.)

    1. Note also that, at least where prostitution is legal, those few women who are nymphomaniacs often become prostitutes,

      Evidence needs citing.
      It’s also a legilsative minefield. Even is prostitution isn’t “legal”, it isn’t necessarily illegal. And from one country in such a grey area, we still get plenty of reports of human trafficking for the sex industry (which is illegal, even though prostitution isn’t illegal).

      1. I know some of them personally?

        In almost all countries, things are legal unless specifically outlawed. In some places some things might be illegal but tolerated, such as leading a billygoat past a church on Sunday in a ridiculous fashion (one of those old laws still on the books somewhere), but usually prostitution is not a grey area in that sense. Do you have an example of somewhere where it is?

        Of course human trafficking is, and should be, illegal, for prostitution or any other reason. If prostitution itself is legal, it is easier to combat human trafficking, for several reasons. First, a legal supply reduces demand for an illegal supply. Second, if prostitution itself is illegal, those involved have less motivation not to commit other crimes, since they are criminals already. Third, punters can report suspicious things to the police without fear of incriminating themselves. And so on.

        There is a significant correlation between that map and ones where homosexuality is illegal, where the death penalty exists, and so on.

        1. Frankly, prostitution laws in most of the world are a mish-mash of ancient insanities, frequently propelled by the lies people peddle under “religion”, and only very rarely challenged or modified by a politician stupid enough to grasp the poisoned nettle (to mix a metaphor.
          Lucky you finding a nymphomaniac prostitute. None of the ones I’ve known ever since being a student (the grant didn’t stretch very far)
          Oh, sorry, watching the F1, and a very … expressive radio message form Verstappen – one very long beep. Then he kicks the tyre. One very not-happy bunny. Time to sell shares in Pirelli.
          Where was I? Girls (and boys) stretching their grant ; mums needing to put food in their children’s bellies ; addicts with a habit to feed. But I’ve never met a “happy hooker” (I think I read that book though.

          There is a significant correlation between that map and ones where homosexuality is illegal, where the death penalty exists,

          I’ve had to pay careful attention to that sort of map after getting re-routed through a death-to-atheists country in the early noughties. Other colleagues getting arrested for going to a gay bar when running a training course (he had cash and a foreign passport, so he didn’t get badly beaten ; he started having worsening mental health after that). Generally we’d strongly advise staff against dipping their wicks when travelling for work, or at least sticking to the hotel’s resident staff. But it’s about sex – people don’t think with their brains.

          Now that was an interesting Grand Prix. When I worked in Baku, my bedroom in the staff flat would have overlooked the track I think – have to look at a street map. So did at least one of the “punter” bars. Bloody expensive drinks! Whitman would probably have written an “Ode to Silicone”.

      2. Sorry, Aidan – conflating all prostitution with human trafficking is a category error.
        There are a LOT of jobs little girls don'[t say they want to do when they grow up and do anyway (work at Wall Mart? Waitress? etc) without it being coerced.

        Many women think “Well *I*’d never do it… so other people must be coerced.” Which is untrue.
        Not to say there isn’t trafficking in places of course.
        I wrote about this for (ultimately various) publications, here first, lately:

        as my state is intending to legalize prostitution. Like Australia, Brazil, some northern Euro countries — all with greater success (for all) than the prohibitionists.

        1. Point the category error at (whoever I was responding to). The various times I’ve walked out of the door to the flat, bumped into a friend and said “what are you doing here?”, to get a “WTF do you think” response, it has all been different people. doing different things for different reasons. Normal life, in other words.

  3. Almost completely off the point,

    a well-liked and trusted individual who would never hurt a fly

    Just how much of a mass-murderer of flies is the average geneticist? I recall an undergraduate “Zoology with genetics” friend groaning repeatedly about having to count yet another cohort of curly/ red-eye/ antenna-legged / other mutation Drosophila to prove a 1:3 or 1:4 offspring ratio. So that’s at least a DrosophilaShipman (several hundred) per geneticist, and our fly-killer is still working towards a BSc.

    There’s a long drawn-out Terry Pratchett joke about how Schrödinger evolved cats into time-travelling organisms with just one thought experiment and a highly motivated thought-cat. So how do the inevitable endochronic properties of evolved Drosophila affect the outcomes of genetics experiments, and possibly more importantly, how did the flies know how to manipulate the results of the first genetic experiments, so Morgan got the “right” results?
    Personally, I blame watching two Poirot movies in one day for thinking like this.

    The conflation of “having sex” and “reproduction” makes it hard for me to work out what is going on in the heads of participants in such experiments. Surely the results are likely to be different between people before and after sterilisation.
    The reported increasing difficult of getting sperm donors, now that you can’t have any confidence in staying anonymous, might also reflect on this.

  4. If physical differences, both between sexes and among groups, are the result of evolution, why not mental ones? After all, our brain is made of cells just like our bodies?

    On that point, and even more basically, it’s worth pointing out the massive difference is sexual attraction. Males are overwhelmingly (roughly 97% of them) attracted to females, whereas for females it’s the opposite, they’re overwhelmingly attracted to males.

    Now that is rather easy to explain from an evolutionary perspective, but rather hard to explain if mental traits such as sexual attraction were just a social construction.

    1. It‘s interesting that many conservatives deny evolution but believe in human nature (e.g. sex differences) whereas many progressives believe in evolution but deny human nature.

      1. That is an interesting point – I wonder if there’s a bit of a likeness to poor J Harlen Bretz and his Missoula Floods hypothesis. The geological community was not at all pleased about it, having just done away with all of the Noachian Deluge nonsense. They were all ‘geology is slow! your floods are too fast!’. But, with diligence and perseverance, Bretz was able to (over many years) collect enough data that he could not be ignored.

  5. I wondered if there is any similar evidence of sex differences in behavior between trans men and trans women? If trans women really are women as the activists say, then trans women would be predicted to be less likely than trans men to have sex with strangers. The work cited in the Areo article seems to be exclusively about heterosexual behavior between people who are not trans.

    Also the correlation with “egalitarian Scandinavian nations” is an echo of the effect of egalitarian societies on sex differences in careers. Recall the Stoet & Geary article and its conclusion that across societies an increase in overall sexual equality led to greater sex differences in career choices. A higher proportion of women choose STEM careers in the worst patriarchal societies. The interpretation was similar to the Areo article: egalitarian societies “set free” individuals to follow their preferences.

      1. Yes, sure, it’s a reasonable hypothesis that many trans women have a same-sex sexual orientation and have just internalized the cultural norms (presentation, physical appearance, behavior) for the majority of people with that sexual orientation (heterosexual males).

        A different hypothesis is that trans women really do have brains that are overall more like the brains of males, including sex with strangers and other sex differences in behavior. That might correlate with or be independent of sexual orientation.

    1. Trans women show levels of sexual assault in line with that of biological males generally, which is thus about 30 times higher than for biological females. They also show much higher levels of aggression and physical assault than biological females, again, more in line with that for biological males generally. As noted above, they also are also much more likely to be sexually attracted to women than are biological females.

      [NB, I am *not* saying that trans women are more prone to violence than men generally, only that they’re more in line with men generally than with women generally; this is thus not a slur against trans women, it’s just a recognition of the nature of men.]

      1. Thanks that’s interesting detail. I would like to read about that if you have a reference?

        Also could I ask: when you wrote “it’s just a recognition of the nature of men” did you mean “the nature of males”? One guesses that trans men would show relatively lower rates of sexual assault, aggression, and physical violence compared to biological males.

        I wonder whether those high male-like rates for trans women overall are lower for trans women who are attracted to males (compared to the larger proportion of trans women who are attracted to females)?

      2. Which -70% ‘lesbian’ and male type frequency of agression and sexual crimes- would support my hypothesis (which is mine), that the huge wave of trans-‘women’ is a kind of ‘small-but-adult’ male orangutan’ strategy.
        A way for less attractive males to gain access to women in their intimacy.

  6. I am assuming that the 100% of women who rejected casual sex were sober. Wonder what the results would be if you asked an equal number of intoxicated women ?

  7. Fascinating stuff. A somewhat related question I’ve had for years is why the pattern of males having visual ornamentation (e.g., the peacock’s tail) to attract choosy females does not seem to be present in humans. Indeed, it seems to be the reverse, at least as would be indicated by a moment’s reflection on who is doing most of the shopping for clothes and cosmetics, getting hair and nails done, undergoing cosmetic surgery, etc.

    With a nine-month gestation period and faced with years of (traditionally) being the primary caregiver for the child after it’s born, it would seem that women have every reason to be the ones being choosy about who they mate with and letting the men doll themselves up to compete for their attention. Humans can see stereoscopically and in color, unlike many other animals, so it’s certainly not a lack of ability to appreciate visual cues. I’m curious what explanations evo psych has offered for this. (I do appreciate that, in a more enlightened age, women do their hair and nails and dress nicely to please themselves and not just attract men, or even primarily to attract men, but there must be a reason why this was the case and continues to be so after thousands of years.)

    1. The male beard is the direct analogy of the lion’s mane. The deep voice is also such a secondary sexual characteristic. But it‘s not just men: women‘s permanent breasts are definitely a secondary sexual characteristic. As to the reverse because more women wear makeup, care about clothes, and so on, that is very probably a cultural thing. There is a huge variation in culture here. Also, at various times in the past (think Louis XIV), men were just as ostentatious as women.

      Until relatively recently, women were seen as oversexed beings who tempted innocent men. As a result, religion has been damning female sexuality for a long time. With cultural mores calling for covering breasts and so on, other things might be compensation. The things which make men attractive, such as success, are still visible, so less reason to compensate with regard to their appearance. Which doesn‘t mean that they don‘t go all out to impress: for every balding bloke in an expensive sports car, there are more than enough women who want to sit in the passenger seat.

    2. I can suggest a possible reason. In humans females may simply judge males more on capacity to succeed as a father and protector, which is not directly associated with physical appearance. This would explain why women sometimes marry older men with high wealth and status who are not particularly handsome.

    3. I’ll leave it to evo-psych people to answer, but I would respond by saying that women do have to make themselves desirable, even if they do the choosing, for most men are at least somewhat disciminating. As for the difference in male versus female adornment, Darwin suggested that sexual selection in humans does work through male choice of competing females, but he waffled on that. But he saw sexual selection in humans as working in a different way from the way it does in animals. All I can say further is that in some societies it is the males who adorn themselves more than do females.

      1. exactly, like the Wodaabe, males presenting themselves ornamented to females for marriage
        makes you wonder about parallels to Birds-of-Paradise male display

    4. In humans there’s considerable male parental investment in long-term relationships, that’s why men tend to be as discriminating as women when choosing a long-term partner.

    5. In hunter-gatherer societies the women and girls are often treated like property and it’s the men who do most of the choosing. Girls are usually married off around puberty and don’t have much say in it. So it’s in the females’ interest to be attractive to attract the best men and incite men to compete for them. It’s also in the mens’ interest to pick pretty females because they’ll give him pretty daughters other men will want and be wiling to compete for. This leads to men valuing female beauty for beauty’s sake.

      The function of the deeper male voice and beards is probably more about intimidating other men than attracting females.

    6. Males used to adorn themselves a lot in earlier times (e g the baroque age). They also used to have long hair. Unembellished males are a relatively new development.

  8. Of course, at some level fear of pregnancy is the reason for the difference. However, it has evolved as a dislike for casual sex among women, just as the goal of having the most offspring has evolved in a desire for sex among men (even if the woman is already pregnant, for sexual practices which cannot lead to pregnancy, even after menopause, and so on). A man can sire a thousand children a year from puberty until he dies. A woman can have, with few exceptions, at most about 20 in a lifetime, and most have far fewer than that. It would be strange if that didn’t lead to the evolution of different behaviour. Obviously, the best strategy for the man is to have sex as often as possible, with a preference for young women who are probably not pregnant (hence the preference for an hourglass figure and for blondes, as hair tends to darken with age). That far overrides any benefit to one or a few children by caring for them. The woman, on the other hand, needs to be impregnated by the best available man, hence the preference for older and successful men: merely the fact that they are old means that their genes can’t be that bad, and success translates into the ability to provide.

    Anyone interested in this should study the phenomenon of groupies. A good musician has access to lots of women, even if not attractive. In the case of rock stars, of course, this is similar to other success, but it is not just that, as a good musician has an advantage even if not successful. The reason is probably because that musical ability is an indicator of fitness which is difficult to fake and immediately apparent. Of course, due to female choice, most men wouldn’t have a chance with the female rock star, but on the other hand that is not what most men dream of.

    One could see where the girls were sitting because the seats were wet.

    These days, becoming pregnant is voluntary, and the macho dudes favoured by evolution are actually disfavoured by many modern women, but it will take a while before evolution has a chance to act on that.

    1. Obviously, the best strategy for the man is to have sex as often as possible, with a preference for young women who are probably not pregnant (hence the preference for an hourglass figure and for blondes, as hair tends to darken with age). That far overrides any benefit to one or a few children by caring for them. The woman, on the other hand, needs to be impregnated by the best available man, hence the preference for older and successful men: merely the fact that they are old means that their genes can’t be that bad, and success translates into the ability to provide.

      I was nodding along until I came to this bit. Is the blonde thing true? I mean, on an evolutionary scale – are there even enough actual blondes for this to be a thing? Is the hourglass figure preferred across cultures? Are women preferentially attracted to older men? These are the sort of assertions that I think make people pause on the ecopsych stuff.

      1. I dunno, Phillip seems to be making a plethora of assertions in this thread — nymphos become hookers; blondes have more fun; men’s beards are homologous to lions’ manes; young chicks dig rich old dudes; the plaster-casters are illustrative of women more broadly — that appear to be based on not much more than what passes for common folk wisdom (and perhaps some personal anecdotes) while providing a dearth of data to back it all up.

        1. All of my claims are commonplace (and referenced) in the evolutionary-psychology literature.

          I‘m quite good at providing references (even for incontrovertible topics), as my publications demonstrate. This is a blog comment, not a scientific paper. Of course, if I were to claim something outrageous, then even here a reference would be in order, but I‘m really just stating the obvious (though perhaps more honestly than some).

          1. It’s sometimes a fine line, I suppose, between the “obvious” and the “commonplace” on one hand and folk wisdom on the other. That’s been one of the main criticisms regarding the bleeding edge of evolutionary psychology; it’s chock-a-block with just-so stories.

        2. Just anecdotally, counsellor Ken: I find I am much more popular with women (flirting, having flirts returned, random compliments, etc. — this is a family blog after all) as an old buck now at 50 than I was as a horney young buck at, say, 25.
          Quite took me by surprise until I read some ev. bio. The reason is because I can “prove I can at least live to 50″… and I have more resources now.


            1. According to Wikipedia, Connery

              was voted by People magazine as the “Sexiest Man Alive” in 1989 and the “Sexiest Man of the Century” in 1999

              when he was aged 59 and 69 years old, respectively. Though I’m not sure whether there was a retrospective aspect to those accolades.

  9. Progressives may claim to believe in evolution, but they (particularly the wokies) are plainly unhappy about it, for three reasons.

    (1) It is too slow, contradicting the romantic attraction of revolutionary change. Notice how even plainly reformist rhetoric like Bernie Sanders’ is dressed up for woke appeal with the magic word “revolution”. Gould’s “punctuated equilibrium”, actually a minor codicil to conventional Darwinism, got considerable buzz from people who didn’t understand much about it for this purely semantic reason.

    (2) It is not egalitarian. Fitter genotypes leave more descendants than less
    fit genotypes—whereas the Associate Dean for Equity requires that every genotype leave exactly the same number of descendants, and this accounting be confirmed by
    DEI committees in every taxon. After all, a less fit genotype isn’t at fault for its
    lesser fitness—which must therefore be a mere social construct. Why, natural selection is not only not egalitarian it is not fair, not socially just!. If most species have gone extinct—why, that is the most unjust situation one could imagine.

    (3) Finally, progressives continually fall into the naturalistic fallacy—confusing is and ought. On the basis of this fallacy alone, evolution by natural selection must be as
    worrisome for the woke mind-set as any more specific scientific finding about nature.

    My hunch is that the occasional woke denigration of Darwin (and of course of Galton, the entire field of Human Genetics, etc. etc.), and their hostility to simple Biology in regard to sexual phenotypes, are all psychological side-effects of this underlying discomfort with the reality of evolution through natural selection.

  10. A thing that is said to be socially constructed (generalizing with any exceptions noted), typically runs in the same vector direction as evolutionary pressures, usually adding amplification, exaggeration and speed. It’s not easy to point to a standalone trait – Sapolski uses the direction of time to illustrate this point using: seconds, minutes, days, centuries before….even the purely socially constructed, if such a thing exists, is inevitably bounded, directed and straight-jacketed by simple algorithms.

  11. Men are our genetic drivers; women are our genetic gatekeepers. Men seek to spread their genes; women seek to acquire the best genes available.
    It’s the perfect set up for our evolution. Men make sure reproduction happens; women make sure reproduction progresses in the right direction.

  12. It would be strange if there were no sex differences, but I believe some effects are overstated (for example, Western men tend to overstate their number of sexual partners unless you correct for this effect by posing the question right).
    I want to make a different point here. Jerry asks: “Why are these sex differences larger in gender egalitarian Scandinavian nations?”
    I find the traditional answer “People can be their true biological sexual selves only in non-patriarchic societies” post-hoc and glib. Northern European influenced cultures are the world-wide odd man out here, but they should get the say what is nature and not nurture in humans sex differences?
    Of all cultures in the world, counterintuitively, the Germanic-influenced ones have the strongest cultural stereotypes about sex differences between male and female. This is true for self descriptions in personality tests, for social rules of behavior (men are not allowed to kiss or hug each other in greeting, but women may, men are not expected to cry etc). The social expectation that women should not be interested in maths and engineering is a lot weaker outside of Germanic countries.
    The thesis that the Germanic culture version of all of this is the natural one is falsified by the fact that in situations of high excitement, like in soccer games after a goal or a loss, men do kiss and hug each other even in Germanic countries where this is not normally accepted.
    All cultures sharpen natural sex differences and inclinations to some degree (see clothing), maybe ours just does it more in some areas where other cultures do it less.

  13. I’m not sure if anyone above already said this, but if it was the case that the sex differences were being driven by fear of getting pregnant or fear of getting an STD, then this would also be a biological sex difference. After all, the reason why only women get pregnant or why women may be more vulnerable to STDs is evolution, not culture.

  14. “As far as pregnancy is concerned, there’s at least one study showing it can’t be the sole factor”

    Perhaps risk of pregnancy is not too important a conscious factor, but it may still be the main underlying reason why evolution has made women reluctant to have sex with strangers. After all, contraceptives are a new thing, so we can’t expect any sentiment regarding sex without risk of pregnancy to have evolved.

  15. There’s this idea in evo-psych that men have two different reproductive strategies, a long-term and short-term. The idea is that for long-term mating men have evolved to prefer young nulliparous girls who have all their reproductive years ahead of them, while preferring peak-fertility women in their 20s when the probability of conception is highest for short-term mating.

    On the surface it sounds reasonable but the data don’t really support it. In traditional foraging societies like we evolved in women grow old very quickly due to the wear and tear of pregnancy and breast-feeding. By the time a woman has got to her mid 20s she’s been through 2-3 pregnancies and lost her youthful physique, her breasts have gone saggy and waist flabby.

    If men have evolved to prefer peak fertility women for short-term mating they would find these parous women highly attractive, but they definitely do not. They say they have “grown old”. The younger girls who haven’t started reproducing yet and still have pert youthful physiques are preferred for BOTH long- and short-term mating and that really kills the idea.

    Men’s willingness to have casual sex is probably mostly just a byproduct of general sexual desire. Since having a quick poke doesn’t cost a man much there’s little reason for evolution to select against it. Men have evolved to find young nulliparous females the most attractive since they have the highest long-term reproductive potential. If the opportunity comes up to have a quicky with one of them many men are likely to take it. It’s that simple.

  16. Sorry to weigh in again.
    Why an intelligent woman should not agree to sexual contact with random attractive men:
    1) you get a fungal infection every time. Attractive casual sex loving males always carry the spores from the last woman.
    2) If you follow them into their apartment, you are not safe, anything might await you there.
    3) If they are not of the superpromiscuous plus superattractive kind, they won’t be content with casual sex. They will follow you home and pester you, make a scene in front of your partner if you have one, or make themselves into a nuisance in other ways. Once when I was still a student and living alone in a rented room, a man (couldn’t hurt a fly!) sat in front of my door for 2 nights and a day. When I left a man I had been with for a very short time who had also so far never hurt a fly he stalked me for 2 years and then tried to stab me.
    4) in my day and time, promiscuous girls were looked down upon.
    I do know women who went along with every casual offer. Usually the ones who had few choices, or very young and inexperienced.
    Probably casual sex is easier, safer and more common today with all the dating portals, I wouldn’t know

    Also, having lots of sex can give you urinary tract infection. This doesn’t happen to men either.

  17. I guess you can take my word based on my “lived experience” that women may not necessarily be thinking about most of these things consciously when propositioned. I think that many women need something other than a handsome face to be “attracted.” Don’t underestimate the power of intimacy and intelligence upon the ability of less attractive men to get the girl. Take Woody Allen as a classic example of this. Although the more attractive/powerful a guy is, the less this might matter to many women I know.

  18. The example of melanin differences as a response to selection makes the universality of some sex differences non-analogous.

    It will be interesting to see if there are robust results, but until then I don’t see how we can control for universal cultural expectations and economical differences. The idea seems to be that sex is independent of its consequences – family formation – and that doesn’t seem fact.

    Sex differences in behavior is likely multifactorial in both gene and environment, so trying to make it all dependent of the XY chromosomes seems fraught with difficulty.

  19. Great article. For people interested in reading more, I recommend “Male, Female – The Evolution of Human Sex Differences” by David C. Geary.

    Couple of other related books, easier reads than the above:

    “Sense & Nonsense – evolutionary perspectives on human behavior” by Kevin Laland & Gillian Brown
    “The Triumph of Sociobiology” by John Alcock.

  20. Wow, Neurotypicals have issues of their own I see. Imagine how amplified it is in the Neurodivergent community.
    I found that if I mask my Autism traits that I get perceived as a suitable mate, but the moment I am just my high-functioning autistic self females tend to want to ‘care’ for me, not copulate 🙂

    Having said that, I finally did find a partner who LOVES my neurodiversity, she finds it very attractive, so I’m good!

    Great post, thanks!

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