What are the evolutionary explanations for why women are physically weaker than men (on average), and is this difference adaptive? See figure one here.

I suppose that something puts pressure on men to be physically stronger than women, but I don't see what it can be. Why the discrepancy between the sexes?

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    $\begingroup$ You should clarify your question, and your reason for asking. I assume that you are asking about a difference in average physical strength of sexes (and evolutionary reasons for this), but the Q can be read in other ways as well. Also, differences in body size/strength between sexes is common in many animals (see Sexual dimorphism), and this is usually not to "dominate women" but often (when males are larger/stronger) used in male-male competition. $\endgroup$ Commented Jul 2, 2014 at 22:43
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    $\begingroup$ For the record, I don't think the Q should be closed as opinion-based. As currently stated, I find it unclear with poor background, but there is a relevant Q on the evolution of sexual differences in humans hiding in there. $\endgroup$ Commented Jul 3, 2014 at 13:28
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    $\begingroup$ I agree. this site is so steeped in the jargon of biology that it can't handle questions from the public. [reopen] The term they need to hear is 'sexual selection' which was broadly discussed by Darwin. Its not entirely incumbent upon the question if the readers misunderstand. Men and women are clear terms that specify human males and females. Fairly precise. $\endgroup$
    – shigeta
    Commented Jul 3, 2014 at 17:04

1 Answer 1


What are the evolutionary explanations for why women are weaker than men (on average), and is this difference adaptive?

All of the theories surrounding this fact are speculative; it would be difficult to prove "why" men are, on average, stronger than women.

One contributing theory is Female-Choice - basically that women had (or has) the ability to be more selective when it comes to choosing a mate. Over time men will reflect the preferences of women (taller than them, stronger than them, facial hair qualities, etc.). This is superficially supported by casual studies like this study from OkCupid where the "attractiveness" curve for men is down-shifted, meaning women think the average man looks below average in attractiveness and implying those who are viewed as average ( actually the top 20% of men or so) would have better reproductive success. Men, in the same casual study, had a nearly perfect bell-curve associated the attractiveness of women, implying that men are excellent at deducing whether a women is below average in attractiveness, average, or above average in attractiveness.

Another contributing theory is Male-Male Competition. Basically men, at some point (and still might) compete with other men to win over women. The bigger, stronger man would presumably win in a fight and eliminate his competition - directly preventing the production of offspring by the weaker male. The male-male competition also holds true in a more speculative theory in that the winners of wars literally raped their way to reproductive success.

It is worth noting that men, on average, are only about 30-40% stronger than women due to the larger muscle fibers in men (as cross-sectional area determines muscle strength, not volume). With training the difference (kg for kg) is reduced to 15-20%.

Ultimately why women are weaker than men (or men are stronger than women - whichever way you prefer to put it) doesn't have a solid answer beyond "because the stronger, taller men have reproduced".

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    $\begingroup$ I find your first subanswer somewhat vague. The Q is probably asking if there are evolutionary reasons why men are on average psysically stronger than women (see Sex differences in human physiology#strength). How strong we are in comparison to other animals isn't really relevant for this question. However, sex differences in species closely related to us is interesting to understand our evolutionary history. $\endgroup$ Commented Jul 3, 2014 at 13:34
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    $\begingroup$ @MCM This is a good attempt at an answer. "The male-male competition also holds true in a more speculative theory in that the winners of wars literally raped their way to reproductive success." This is a rather grim prospect, but I would entirely believe it as a driving force in our selection. Is there any citation or study into this? $\endgroup$
    – James
    Commented Apr 26, 2016 at 9:28
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    $\begingroup$ Moreover, the male-male competition and the success of the stronger man should lead to evolution of stronger humans (both men and women). If it has more effect on males then there is something that pertains to the activity of Y-chromosome. This would finally boil down to whether androgens have a positive role in promoting muscle development (more than estrogens). $\endgroup$
    Commented Apr 26, 2016 at 9:46
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    $\begingroup$ @WYSIWYG Not necessarily, selective pressure on one sex does not have to have any effect on the other. $\endgroup$
    – John
    Commented Mar 21, 2017 at 15:54
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    $\begingroup$ but can you explain WHY all of these possible reasons are sex-specific? Whether it be 'Female choice' or 'Male Male competition', why wasn't it the other way round, like 'Male Choice' or 'Female Female competition' ? $\endgroup$
    – user1995
    Commented Apr 7, 2017 at 11:32

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