A standard principle in evolutionary biology is that the sex that invests the most in reproduction is the most choosy when it comes to picking suitable mates. In most mammals, this means females because of the heavy cost of gestation. In humans, the huge reproductive investment difference between 9 months for females and 9 seconds for males makes the imbalance quite pronounced. Okay fine, let’s say 9 minutes for the male evolvify readers out there. It would hardly make a dent if that was 9 hours or days or weeks. The order(s) of magnitude cost disparity predicts that women should have evolved to exercise ultimate “mate choice” in terms of human sexual selection. That’s a pretty easy case to make from a biological standpoint, but how does that translate to our modern world?

First, we do need to add some qualifiers that would have existed in the environment of evolutionary adaptedness (EEA). The main non-biological cost that would have been generally persistent over time is the social component. In a world of hunter-gatherer bands with almost pervasive contact with kin and known individuals, men did have real potential social costs. In some instances, these costs would have been real to the point of physical inducement. From a pure social perspective, the variability of social norms and potential for geographic distance makes it hard to draw modern general parallels in this regard. So this cost is something to consider, but it’s not easily factored into the discussion in a reliable way. For now, let’s just say that men do have some non-biological calculations with respect to reproductive investment.

Excepting social costs, we would expect men in the EEA to be motivated to attempt to reproduce with any and all available females. While this motivation may still exist, we don’t see see this carried out by and large. Something has changed.

The main disconnect from the EEA to today is the legal reification of male parental investment. The introduction of authority enforced child support effectively negates the extreme imbalance pervasive throughout human evolution. Arguably, the roles of parental investment are reversed. Kanye West is quick to point this out in his song ‘Gold Digger’. Some legal structures are such that males are liable for 18 years of financial investment set against 9 months of biological investment by the woman. Granted, this is an oversimplification as time investment needs to be factored in as well. Again, the variability of circumstances and legal differences makes it difficult to generalize. And, all of this is amplified by the cultural and religious imperative toward lifetime monogamy.

This shift poses interesting questions for human wellbeing. Human brains evolved under the extreme imbalance in male-female investment. Remnants of this influences emotional motivations and cultural mores in-turn. Both of these conflict with the new parental investment paradigm. What are the impacts of this mismatch in terms of behavior and psychological health?

In terms of behavior, we should expect to see an increase in male choosiness commensurate to the increase in male investment. In practice, this may present as an adoption of stereotypically female behaviors by men. This could range from things like coquettishness to the traditionally female role of objectification of males based on physical attributes. In fact, we have seen a rise in male propensity to make mating judgments based on physical characteristics – much to the objection of women. How does this translate to things like the feminist movement? The nuances of this paradigm shift likely ripple throughout society in ways that aren’t obvious and aren’t always positive.

What implications should we expect to see with this collision of legal structures and biologically influenced motivations? Does another balance need to be struck? Do the legal pressures effectively accomplish their goals?

  1. wozza 10 years ago

    You might like to read “Sex At Dawn“. The authors argue that we evolved with multi-male, multi-female relationships. All men looked after all children, because no man could be sure that whose child was whose! Of course, this all changed with agriculture, people beginning to live in one place, thus the concept of property. Anyway, I might not have done the book justice, read it for yourself, it will definitely challenge the way you think about human sexuality and reproduction.

    • Andrew 10 years ago

      Yes, I've read it. I wish I would have written my thoughts on it at the time because it's interesting, but I remember finding fundamental flaws in the arguments. And of course, now I can't remember what they are so I have to reread it so I can talk more intelligently about it. So all I can say for now is… yes, it's worth reading, but only if taken with many grains of salt.

  2. David Csonka 10 years ago

    It would be interesting to see what would happen to marriage rates if vasectomies were perfected to the degree that there was no risk of permanent sterility, and they could be reversed or reinstituted on a whim.

    • southbaltimorecf 10 years ago

      I have been saying for a very long time, that many problems would be solved if we:

      -Perfected vasectomy reversal
      -Mandated vasectomy at birth
      -You would go to a clinic, post 18 (or earlier with parental consent), and at no cost to you, sign an acknowledgment that you are "loading the tubes" and get the reversal

      Of course, this would likely cause a few problems as well, such as rampant promiscuity. That is, of course, until the great homeostasis was restored by the evolution of yet more sinister forms of STD.

  3. Emily 10 years ago

    "The Red Queen" also puts forth several theories. The author contends that most human relationships in the past were monogamous, not polygamous, as in hunting/gathering it worked out so that men with one family each were better off in bringing back the right amount of food. Only in the case of agriculture and/or gathering of resources to one chief or king do you get harems (so a lot of cloistered women and a bunch of single peasant men with no chance of reproduction and perhaps a surly attitude). He seemed to feel it is better to compare us to certain bird species than to other primates in this regard. Women in this model are motivated to marry a "good enough" husband who will be kind and sure and stick around and raise the kids, and then cuckhold him with the best guy out there for the best guy's genes (certain species of birds do the same thing).

    • Emily 10 years ago

      Given that genetic testing has shown that a high percentage of children are not their mother's husband's offspring (I'm doing this from memory, but I think it is 1 in 6 in a couple different studies in Europe), this may well be happening. It certainly sounds like a reasonable theory to me, but I'm not sure how it would translate into male choosiness. In "The Red Queen" the rampant sex and large testicles of humans compared to most primate species seemed to be a bit of biological proof for this theory – ordinary responsible guy needs to get as many chances as he can to make sure the offspring are his. Mr. Cuckhold and the Mrs. have to sneak around and don't get as many chances, perhaps mathematically favoring the dedicated husband.

      • @melissamcewen 10 years ago

        As per illegitimacy http://www.straightdope.com/columns/read/2730/who
        And the rate is even lower in certain populations that are religious and/or wealthy. I'm not sure whose hat I'm throwing things in with- Sex At Dawn or The Red Queen, but I think it's quite apparent that things have changed since the paleolithic perhaps due to the social structures Andrew is talking to. Sex at Dawn tantalizingly mentions that societies that have been agrarian for the longest time seem to have men with the smallest penises. I'd like to see more data on that (though perhaps not personally). I wonder if it has something to do with how heavy punishments are on adulterous women.

        Andrew have you seen Blue Valentine? The woman gets pregnant by a big hulking bloke and the child is raising by her nice, kind, and unambitious boyfriend/later husband who she later loses attraction for. It's an incredibly sad movie and perhaps about the dualism in female sexuality that evopsych has uncovered.

        This neanderthal study that just came out that posits patrilocal mating behavior is interesting "Genetic evidence for patrilocal mating behavior among Neandertal groups"

        • Andrew 10 years ago

          Note that these paternity numbers are almost useless in evaluating the evolutionary significance as they are distorted by birth control. When dealing with evolved emotions and behaviors, it’s important to maintain the perspective of the impulse, not its result (or lack thereof) in modernity.

          The penis size thing (if true) almost has to relate to reproductive control by patriarchy or religion. Specifically, sex would have been used as a fitness cue prior to these developments. Thus, female mate choice would likely have influenced male sex organs. The emphasis on virginity and “no sex before” marriage negates women’s abilities to use sex for sexual selection. This would toss the characteristic back into genetic drift.

          I haven’t seen Blue Valentine, but I don’t mind watching sad, sappy movies… In the name of science of course.

        • grace 10 years ago

          Provocative post per usual…

          RE: shrinkage over millenia

          Have you come across this story yet? http://www.scientificamerican.com/article.cfm?id=http://blogs.discovermagazine.com/discoblog/2011/

          Would love to hear thoughts… Bigger brains naturally associate with birthing into bigger birth canals, hence bigger/longer penises. I am not surprised whatsoever if the most agarian societies associate with smaller brains and also smaller penises. Makes evolutionary sense.


    • Andrew 10 years ago

      The bird comparison is likely for reasons of "pair bonding". It's relatively rare in not just primates, but all mammals, and common in birds.

      I have to reread The Red Queen. I read it before I really got into the nuts and bolts of this stuff and it's a blur in my memory.

  4. Guest 10 years ago

    So….don't trust women?

  5. Author
    LLGWright 10 years ago

    "males are liable for 18 years of financial investment set against 9 months of biological investment by the woman"
    I cannot help but find fault with this argument, since the financial investment is not completely unilateral – especially as court-ordered. There is absolutely no way that most children could be financially supported on the child-support payments alone. Mothers will continue to share in the financial support and investment in addition to the physical investment.

    • Andrew 10 years ago

      Yes, it's a generality and there are a lot of variables. The context I provided in the previous sentence of the song is in reference to men with significant financial means; a small percentage of their income would negate the requirement for the woman to work. But yes, taken out of context, I would have to agree that each case is different.

      However, your point doesn't at all negate that legally imposed financial obligations for men now exist, and that their implementation is a recent development.

      • Emily 10 years ago

        Another point the Red Queen (sorry to keep harping on that book) makes is that it is only since recent (Victorian – darn that Prince Albert) times that men have dressed so soberly compared to women.

        • Victoria 10 years ago

          When ever I think about the Victorian era I remember one of my favorite college profs (taught a Darwin class and a Darwinisms class, actually) who described that as the prudish era when women's sexuality decayed to 'Lie back and think of England'. I just looked it up, and it would be great (and terrible, really), if the source of the line 'lie back and think of England' is the following: I am happy now that George calls on my bedchamber less frequently than of old. As it is, I now endure but two calls a week, and when I hear his steps outside my door I lie down on my bed, close my eyes, open my legs, and think of England. (From Wikipedia :http://en.wikipedia.org/wiki/Lie_back_and_think_of_England )

  6. Author

    […] This post was mentioned on Twitter by Craig Zielinski, Wesley Gee and B.A.M.F Athletics, David El Achkar. David El Achkar said: Sexual Selection Reversal: The Rise of Male Choosiness http://bit.ly/hV23f7 (via @evolvify) […]

  7. Calvin 10 years ago

    Any hunter-gatherer research on this? Seems like looking at groups that live much more closely to our EEA than the modern world could help answer some of these questions.

  8. PettyBetty 10 years ago

    Seeing as how it's extremely unlikely that any one woman becomes pregnant from a single sexual encounter, wouldn't it have also made sense for ancient man to lay claim to only as many women as he could have sex with regularly enough to ensure pregnancy? I don't really understand the logic of the "men evolved to have sex with anything that moved" theory. That would involve a huge expenditure of energy going from woman to woman in a time when most energy was devoted to finding food and there was no transportation, and it wouldn't even be a very effective way of producing children! Seems to me evolution would not only favor men who expended a ton of energy being promiscuous but also men who picked one woman and hung around long enough to sleep with her while she was fertile. Social niceties like having someone warm to cuddle with through long cold nights on the Savannah also seem like they would have favored pair-bonding instincts…

    • Andrew 10 years ago

      This analysis isn't necessarily wrong, but it puts a little too much weight on choosing one strategy or the other in terms of optimization. The optimal answer is… both, simultaneously.

  9. Pepper 10 years ago


    I think I’m missing something. Since when is it a traditionally “female” role to objectify men based on physical attributes? It has been my understanding that both males and females use physical markers as indicators of the ability to produce healthy offspring. Moreover, these days we do see that men make mating judgments based on physical characteristics, but according to which data or hypothesis can we infer this is an increase compared to the past?

    • Andrew 10 years ago

      "Since when is it a traditionally "female" role to objectify men based on physical attributes?"

      Objectification isn't the scientific term of course, but females use physical cues in female mate choice across species, humans in particular.

  10. Jamie 10 years ago

    Check out the book The Game, or google "pick up artist" (PUA). There is a men's movement or community that aims to gain skill in courting, but the unspoken reason of it is essentially the purpose of 'role reversal' in mating. A man well skilled in courting will ultimately have more decision power in the mating process as opposed to the current model for males to court and 'hope' to be selected by a suitable female.

    • Andrew 10 years ago

      I've read it. I'm not sure that it has anything to add in reference this post per se.

  11. angus 10 years ago


    I'm sorry but choosing based on physical attributes has been a traditionally male role for thousands of years. Since the introduction of wife as property.
    Empires kidnapped the women they found attractive and of child bearing age, men chose less hairy females with characteristics that indicated fertility.
    You are forgetting rape is a BIG part of our evolution.
    And women, have menses that they cannot control and don't posses signals like other species to indicate when they are ovulating.

    In ancient Rome women of low intellect were preferred because the lower the intellect the the higher the number of children they would give birth to, for example.
    And the women were owned by there fathers.
    That is why women are considerably less hairy than men. If the women were the ones who chose we would have way bigger men in comparison to women.

    Also, there is no indication that we ever had a matriarchal society.
    So i would say the reversal you are talking about is women becoming choosier for the last 100 years or so.

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