Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why are women not as strong as men?

  1. Aug 13, 2013 #1
    What evolutionary advantage does it serve? Is the lack of physical strength simply a biproduct of being able to give birth? It seems strange that those who produce the young would not be able to defend themselves most efficiently.
     
  2. jcsd
  3. Aug 13, 2013 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Are women not as strong as men? In what sense?
    What studies are you using to support that supposition?
     
  4. Aug 13, 2013 #3
    Are you kidding? Its well documented in fitness, strength training and body building circles.
     
  5. Aug 13, 2013 #4

    Monique

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    If you're not strong you'd better be smart :biggrin: But really, why would more muscle lead to better survival? It takes more energy to maintain them.
     
  6. Aug 13, 2013 #5

    DavidSnider

    User Avatar
    Gold Member

    Have you read 'The Selfish Gene'? I think it does a pretty good job of answering questions of this kind.
     
  7. Aug 13, 2013 #6

    Ryan_m_b

    User Avatar

    Staff: Mentor

    Not every trait has been selected for because it is an advantage to physical fitness, it could also be a neutral trait or even a deleterious one sexually selected (like peacock tails). Trying to explain everything we see in terms of advantageous selection is fallacious and can lead to some very bad science.

    For more information about the differences between sexes I suggest looking up sexual dimorphism.
     
    Last edited: Aug 13, 2013
  8. Aug 13, 2013 #7

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    I'll give you an example: pound for pound, women's muscles are as strong as men's - they are made of the same stuff - so men and women with the same muscle mass should perform comparably in strength tests. So who is being compared?

    Also you are assuming that everyone is thinking of strength the same way you do - this may well be the case, but I'd prefer not to make that assumption.

    Getting you to be specific should help expose the underlying assumptions.

    But the question does have other underlying assumptions that I was confident others would bring up :)
     
    Last edited: Aug 13, 2013
  9. Aug 13, 2013 #8
    I had this doubt too ,why would some set of genes survive for 100's or more generations if it does not provide any advantages ,it's not just about humans by the process of natural selection ,it should have been eliminated long ago.
     
  10. Aug 13, 2013 #9

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    Monsterboy, did you read Ryan's post? The advantage provided by being muscular may have nothing to do with "fitness". That human males are, on average, bigger and stronger than are females is an example of sexual dimorphism. Evolution can get pretty weird when differences amongst the sexes comes into play. Ryan's post mentioned peacock tails. Another example: Male deer have huge antlers while females have little tiny ones (if any). Those huge antlers don't help the male deer survive. To the contrary: Those big huge antlers are deleterious with regard to survival. What those antlers do do is to help them have offspring.
     
  11. Aug 13, 2013 #10
    Physiologically, men are stronger than women because they have more muscle mass, which is because they have much more of the hormone testosterone. But the evolutionary reason for this is that humans are social animals who have always lived in groups. Hence, rather than each individual being completely self-sufficient, it was advantageous for a division of labor to take place. Since women were burdened with pregnancy anyways, it made sense for the men would do all the hunting and defending while the women would take care of the children (which is a massive burden) and do some types of manual labor (e.g. foraging and, I guess, paleolithic housekeeping). In particular, this was important for our species because humans children take a much longer time to reach physical and mental maturity than most other animals (which probably has something to do with our much more complex and adaptable brains) and probably for other reasons that I do not fully understand (e.g. pregnancy seems to be unusually onerous for our species compared to others). Anyways, all this means that women didn't need to be as strong as men (and muscle takes a lot of extra food energy to maintain, as previous posters have discussed), so they became weaker.
     
  12. Aug 13, 2013 #11
    Absolute strength. The ability to pick up a weight and move it.

    Anyway, I was just wondering if there was a definite answer. I can understand a lower caloric intake as beneficial, but if women were supposed to be the ones not hunting, then wouldnt it make sense that men have a net lower caloric intake so they could hunt for a longer period of time?
     
  13. Aug 13, 2013 #12

    micromass

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    What you don't seem to realize is that it isn't so much about being the fittest or to be as efficient as possible, rather it is about things that are sexually advantageous. That is: how can we maximize the number of offspring we have. A possible answer should be looked for in that direction.
     
  14. Aug 13, 2013 #13
    Caloric intake doesn't directly effect the duration for which one can hunt, in the short term. But a lower caloric requirement would certainly be desirable anyways, if it were feasible. However, in order to be effective hunters at all, men needed to have a certain amount of strength, which requires a certain amount of muscle mass, which requires a higher caloric intake.
     
  15. Aug 13, 2013 #14

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    That's a nice cooperative story, but it's not right from what I've read. In other species that display sexual dimorphism the reasons are polygny, female mate selection, and male-male competition. That's what happened with us. We are who are are in part because our male ancestors were violent murdering rapists. Amongst ancient humans, males oftentimes died young in violent deaths. A big hulking male is more likely to survive a violent encounter with other males and to father offspring, particularly if he and big hulking cohorts just killed all the males and children and then raped all the women in the nearby tribe. When females did have a choice in mates, they chose the big hulking male, perpetuating the cycle.
     
  16. Aug 13, 2013 #15
    Haha, I definitely don't doubt that's part of the story. However, it doesn't explain why most women are so weak - too weak to be self-sufficient in the wild, let alone hunt large creatures, or so it seems to me as a woman who frequently attempts weight training (although I'm assuming they've always been this weak, which might not be true). Additionally, female weakness would necessitate that the women be provided for at all times by a sufficient number of males in order to successfully bear and raise children, so that would seem to restrict the extent to which men could run around and fertilize as many women as possible. So I think the division of labor thing is still a large part of it, plus it jives with how most hunter-gatherer peoples live today as far as I know, but I'm no expert.
     
  17. Aug 13, 2013 #16
    I believe Ndaren's description above makes the most sense.

    Women are not as strong, in general, as males because they don't need to. Isn't that Selection? Why waste energy on muscle mass if it's not needed? The resources can be utilized more efficiently in child birth and child-raising if a strong male is around to support mother and child.

    It makes sense to me that Selection, over many years would favor females utilizing their limited resources towards developing efficient means of procreation and child raising, in an environment of male support, over other females that wasted their resources on muscle mass at the expense of less-efficient reproductive strategies.
     
    Last edited: Aug 13, 2013
  18. Aug 13, 2013 #17

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    Ancient humans didn't need strength to hunt. They needed cunning and endurance. It takes very little strength to kill an animal that is already dead, and that is mostly what our ancestors ate. It doesn't take much more to kill an animal that is near dead because it has been chased for hours until it collapses. Upper body strength and running endurance go counter to one another. The best long distance runners are scrawny. Males aren't bigger and stronger because their male ancestors were the hunters of a hunter-gatherer society. It's some other reason, and all one needs to do is to look to other species that exhibit sexual dimorphism. It's almost always species that have extreme male-male competition, polygny, female mate selection, or a combination of these three.
     
  19. Aug 13, 2013 #18
    Then why do people "fall in love" with each other and chose to be monogamous for at least some period of time? Im not an expert but I think a good fraction of why women and men are different is simply chance or rather, probability functions.
     
  20. Aug 13, 2013 #19

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    most women?
    Now that demands the research to back it up more than the original post.
    It's one thing to say that women can generally lift less weight than men (OPs definition for "strength" - not specific enough but the thread has moved on) and quite another to say that most women are able to lift so little that they are unable to survive unaided.

    The usual picture is that humans are evolved as social animals - a single human cannot be self sufficient "in the wild" for long.

    Ndaren's picture is very seductive - especially to men - but it is a somewhat simplistic and suspiciously self-serving picture which has been called into question. i.e.

    Owen L. R. (2005) Distorting the Past: Gender and the Division of Labor in the European Upper Paleolithic [book] ISBN 3-935751-02-8

    ... and a whole swathe of social anthropology and paleoanthropology papers indexed through scholar.

    Everyone else seems to be handling the evolution angle - I'd like to emphasize that attributes that are not actually helpful to survival must still survive through many generations, or evolution cannot work. There has to be diversification within a population - for eg - which means that not everyone will be optimized for survival. All that is required is for that bit of DNA to get passed on to the next generation. It needn't actually do anything at all. Something becomes a characteristic because it helps this process along. Life is complicated and messy and does not care about our simplistic beliefs.
     
    Last edited: Aug 13, 2013
  21. Aug 13, 2013 #20

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook