Why are women not as strong as men?

[Aero51]

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.

 

[Simon Bridge]

Are women not as strong as men? In what sense?
What studies are you using to support that supposition?

 

[Aero51]

Are you kidding? Its well documented in fitness, strength training and body building circles.

 

[Monique]

If you're not strong you'd better be smart But really, why would more muscle lead to better survival? It takes more energy to maintain them.

 

[DavidSnider]

Have you read 'The Selfish Gene'? I think it does a pretty good job of answering questions of this kind.

 

[Ryan_m_b]

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.

 

[Simon Bridge]

Are you kidding? Its well documented in fitness, strength training and body building circles.

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 :)

 

[Monsterboy]

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.

 

[D H]

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.

 

[Ndaren]

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.

 

[Aero51]

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?

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 wouldn't it make sense that men have a net lower caloric intake so they could hunt for a longer period of time?

 

[micromass]

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 wouldn't it make sense that men have a net lower caloric intake so they could hunt for a longer period of time?

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.

 

[Ndaren]

I can understand a lower caloric intake as beneficial, but if women were supposed to be the ones not hunting, then wouldn't it make sense that men have a net lower caloric intake so they could hunt for a longer period of time?

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.

 

[D H]

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.

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.

 

[Ndaren]

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.

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.

 

[jackmell]

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.

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.

 

[D H]

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.

 

[Aero51]

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.

Then why do people "fall in love" with each other and chose to be monogamous for at least some period of time? I am not an expert but I think a good fraction of why women and men are different is simply chance or rather, probability functions.

 

[Simon Bridge]

most women are so weak - too weak to be self-sufficient in the wild

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.

 

[Simon Bridge]

I'm not an expert but I think a good fraction of why women and men are different is simply chance or rather, probability functions.

And how are the probability functions shaped?

Aside: people bring up "love" in the context of evolution all the time - have you tried looking it up?
i.e. http://www.percepp.com/lovempat.htm

monogamy is also well researched - recently: http://www.nature.com/nature/journal/v500/n7461/full/500125b.html

 

[Aero51]

Thanks for the links. I have no idea, though I came up with a back of an envelope model which is basically a string on conditional probabilities. It would most likely have fractal properties

 

[Simon Bridge]

Those "string of conditional probabilities" models are the kinds of things that tell creationists that evolution of eyes and flagellum motors and stuff cannot happen - you need to include "feedback loops" and "scaffolding" and "arms races" and so on in the model as well. These skew the probabilities by allowing some parts of the chain to be visited many times: it's as if you had a probability tree that looped back on itself.

It does take a while to get used to how evolution happens and the kinds of things to expect as a result.
Fractals are a good metaphor - they include the feedback mechanism.
Also visit stocastics and cellular automata. They help.

But I think the core thing you need for the evolution side is to realize that a trait need not be helpful to survive - evolution does not care about that. It only needs to be able to get passed on to the next generation and that is all.

To see through a magic trick you have to keep reminding yourself that it is a trick - to see how odd evolutionary effects happen you have to keep reminding yourself that evolution does not care about fitness. Does the effect kill the organism before it can reproduce? No? Then it can continue. (...doesn't mean that it will.)

 

[Aero51]

I love stochastic models, especially in fluid mechanics. That's actually one area I'd love to end up. Evolution is certainly interesting from a mathematical standpoint.

 

[Ndaren]

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.

To be totally clear, when I said self-sufficient in that case, what I meant was I don't think that an isolated paleolithic group of women would make a robust survival unit, or at least they wouldn't fare as well as a similar group of males. I am simply generalizing from my experiences and observations and those of others I have discussed this with. Thus, I think the burden of proof is more so on one who claims that women's bodily strength is optimum for survival without males (again, disregarding intraspecies combat), but I would be interested in seeing evidence supporting or discrediting either possibility.

D H : I am well aware of what you discussed about scrawny long distance runners and the strategy of chasing animals to exhaustion. But we, or at least I, do not know that this is how humans have always captured all their prey (I'm under the impression that it isn't, at least not after we migrated out of Africa), or that this was the most power-intensive task they had to deal with, or that all animals could be finished off with little strength, or whether the lesser strength makes women slower runners and too slow to be equally effective hunters, etc. So I'm not convinced yet. Furthermore, seeing as humans seem to be the exception to the animal kingdom in many ways, especially socially, I would not compare them to other animals regarding the evolutionary forces that shaped their group behaviors. But ultimately, if women's lesser strength incurs any disadvantage upon a hypothetical group of paleolithic women not burdened with intraspecies combat, that means it must be to some extent a result of division of labor (assuming that evolution has fully optimized this aspect of our species). On the other hand, if no such disadvantage exists, I would be very inclined to accept your explanation of the difference in strength.

 

[Simon Bridge]

To be totally clear, when I said self-sufficient in that case, what I meant was I don't think that an isolated paleolithic group of women would make a robust survival unit, or at least they wouldn't fare as well as a similar group of males. I am simply generalizing from my experiences and observations and those of others I have discussed this with.

Generalizing from personal experience - well we all do that don't we. In a scientific forum, it is probably a good idea to be careful of subjective opinion based on personal experience and biased along social lines and when we are making a statement of fact backed by science. That would go double for a subject that has political overtones.

But what do you mean by "robust"?
You seem to have gone from saying that women cannot survive without male assistance to saying that they can survive without the men, just that they survive better with men?

Surely the same is true of men too? i.e. perhaps humans survive best in a mixed gender group?
Perhaps you just happen to have talked to a lot of men - thus the bias?

Thus, I think the burden of proof is more so on one who claims that women's bodily strength is optimum for survival without males

I'd go along with that, however, I don't think anybody has made that claim so it is irrelevant.

The claim under examination is that "women are too weak to survive in the wild".
I suspect that any man making such a claim in front of women will find their chances of reproduction somewhat reduced ;)

but I would be interested in seeing evidence supporting or discrediting either possibility.

Fair enough.
https://www.amazon.com/dp/1580051065/?tag=pfamazon01-20
If you would like to make a new thread?

 

[D H]

monogamy is also well researched - recently: http://www.nature.com/nature/journal/v500/n7461/full/500125b.html

And another recent article by the same author, this one in PNAS: http://www.pnas.org/content/early/2013/07/24/1307903110.

That said, there are others who have rather different explanations of human monogamy. There apparently is no consensus. I'll leave those other explanations up to others to find; I personally find Opie's explanation to be quite apt.

To see through a magic trick you have to keep reminding yourself that it is a trick - to see how odd evolutionary effects happen you have to keep reminding yourself that evolution does not care about fitness.

To the contrary! Evolution cares a whole lot about fitness. It's just that what we think of "fitness" has little to do with fitness as far as evolution is concerned. The evolutionary fitness function is

• Rather broad. Non-exemplary specimens still have offspring, and their offspring have offspring.
• Extremely short sighted. Evolution does not have a plan. If it did, it wouldn't select for peacocks with ridiculous plumage that hinder flight and make the bird easily visible to predators far and wide. But since that ridiculous plumage drives peahens wild (anthropomorphizing here: "I want to have his babies!"), that's what get passed on.
• Grossly inefficient. As a search function for some optimum, evolution is slow, random, and sub-optimal.
• Quite amoral. Killing all the males and young can be a very good evolutionary strategy for males. It's what lions do, and it apparently is what ancient human males did, at least to some extent.

So I'm not convinced yet.

Google the phrase "endurance running hypothesis".

With regard to brutality as the root cause of sexual dimorphism, perhaps this will help convince you.

This is from the seminal book War Before Civilization: the Myth of the Peaceful Savage by Lawrence H. Keeley. Keeley looked at various hunter-gatherer societies today as a stand-in for our hunter-gather ancestors. Our ancestors were not a bunch of pastoral peaceniks. Anything but! They were brutal. Evolutionary success for our ancient human male ancestors wasn't about skill in hunting animals. It was about skill in hunting other human males. Males are brawnier than females, particularly in upper body strength, because the meanest, baddest SOB around was much more likely to have offspring that begat offspring than lesser males.

Hooking up with this badass SOB was the best evolutionary strategy for females. The second best strategy was to be unfaithful to ones spouse and hookup with this SOB and have his babies. As I said above, evolution is markedly amoral. If infidelity makes for offspring that are more likely to beget offspring, evolution says yes, be unfaithful.

Why males are stronger than females, particularly in upper body strength, has little to do with hunting skills. It's all about what we would call criminal behavior nowadays. You can still see signs of it today. Many females prefer men who are a bit "edgy". Bad boys, in other words.

 

[Ndaren]

Generalizing from personal experience - well we all do that don't we. In a scientific forum, it is probably a good idea to be careful of subjective opinion based on personal experience and biased along social lines and when we are making a statement of fact backed by science. That would go double for a subject that has political overtones.

I thought it was generally known and accepted that men are often obliged to help women with the more physically demanding aspects of daily life (e.g. moving furniture, carrying heavy loads, etc.) and industry (e.g. logging, construction), and hence that paleolithic women may also have had trouble doing certain things without male help. If one demands that every statement, regardless of how controversial it may or may not be, be supported by scientific citations, then discussion of any sort (including this one) would become nearly impossible.

You seem to have gone from saying that women cannot survive without male assistance to saying that they can survive without the men, just that they survive better with men?

Surely the same is true of men too? i.e. perhaps humans survive best in a mixed gender group?
Perhaps you just happen to have talked to a lot of men - thus the bias?

I'd go along with that, however, I don't think anybody has made that claim so it is irrelevant.

The claim under examination is that "women are too weak to survive in the wild".

The question I am emphasizing is whether the difference in strength between men and women (other factors are irrelevant to this debate, as far as I can tell) would give a group of women a survival disadvantage, which is what I originally meant by the statement about women 'being too weak to survive...'. This is a decisive question regarding whether division of labor was a factor in the strength difference. If the answer is affirmative, that directly implies division of labor (unless someone can propose a different explanation for it). Thus, in order to argue that division of labor was not a factor in the strength difference between sexes, one must claim that the answer to that question is negative - i.e. the amount of bodily strength women possesses is optimal for all the tasks of paleolithic living, excepting war.

D H: I do not at all deny that our male ancestors engaged in combat with one another and that this would have favored the more muscular among them, which is obviously true, as illustrated by the data you posted (if you look at my original post I did briefly mention that men did this). I am only concerned with whether, in addition to that, women became weaker. If anything, men evolving greater strength for intraspecies combat could have encouraged a strength-based division of labor between the sexes, causing women to become less strong than they initially were.

None the less, D H, I now think you are correct that, at least for most of prehistory, intraspecies combat was the primary reason for superior male strength. Among other things, this would help explain why I have heard of ancient, as well as modern day, paleolithic- and mesolithic-type communities in Africa and pre-Columbian North America where women apparently did just about everything –including some physically demanding tasks – apart from hunting. For various reasons I wouldn’t rule out that division of labor became a factor at some point in our evolutionary history (perhaps primarily outside of Africa), which might explain why it is, to my knowledge, common in the civilizations of the last 2000-3000 years and why white women are less muscular than black women (here's my citation: Am J Clin Nutr June 2000 vol. 71 no. 6 1392-1402 ), although the same goes for white men compared to black men. But it is not important to me what the exact story is, and we have probably answered the OP’s question as well as we can, so I feel no need to continue this discussion. Thanks all for informing my view of ancient human gender roles.

 

[Aero51]

I always though blacks were not necessarily stronger but have more fast twitch fibers, where as whites have more slow twitch.

 

[bobze]

Before you guys doubt DH and perpetuate the classic "males are evolved to be hunters" clap trap (that does wonders for our egos). Stop and think about other species like he suggested. Especially social ones with strong male-male competition.

Look at lions. Male lions aren't good for much except fighting each other, killing cubs and knocking up the females and occasionally joining in a hunt. They aren't fearless hunters, their lazy and use that size and bulk to ensure they get more mates. Not to hunt.

Next look at another social animal that doesn't hunt, like the American bison. Big, bull males can weigh up too 2000lbs and are much larger and "stronger" (meaning here they have much more muscle mass, not an inherent difference in muscle fiber strength). By this 20th century male-misogynist argument/myth, male bison should be hunters and damn good ones. Huh? Male bison are "big and strong" for the same reason that male lions are, and it has nothing to do with hunting. Nor does the size difference in white tailed deer, or male chimpanzees or male gorillas or male elk or hundreds of other examples, have anything to do with hunting.

Its a pretty silly (I'd say even stupid) argument that humans are somehow unique in this aspect of evolution and that males selectively evolved to "hunt". Whats more likely, is human males (like other social sexually dimorphic animals) evolved their sexually dimorphic traits for similar reasons. So like Ryan said, I would read up on that.

 

[jackmell]

I too have reached the conclusion from this thread that male strength over females is a consequence of mating competition between males. At least I believe that is the results from this discussion. So for the question of why are males stronger than females, the answer is I believe because of mating rituals. Or no?