Women are weaker. . .

Is there a biological justification as to why females are weaker in sheer strength than males? When mankind first developed was there a good reason for women to develop weaker physically than men?

I don’t know about justification, per se, but I think that muscle development is directly related to testosterone levels. Since men have a lot more testosterone than women, I believe that explains it.

I’m sure a rabid militiaman might be able to ‘justify’ it.

You might have an easier time understanding the issue if you asked why males developed larger, stronger frames than females rather than asking why females are, in general, smaller. I’m no genius, but I’ve always thought this was a pretty simple issue. Males and female behave differently. Just looking at humans, we see that the females spend a great deal of time nurturing and caring for their offspring while males are off collecting food and defending territory.

This separation of function is not quite as obvious now as it was back in the days when a man’s average day at the office involved smashing the skull of some unsuspecting critter and dragging it home to be hacked apart with the sharp stone that was used a few hours earlier to kill the guy that tried to conquer the water hole. The male frame evolved to be larger and stronger out of necessity. Females did not have so much need for strength and bulk because they have always been able to sucker men into doing physical work for them. Rather, they had needs for stored body fat in all the right places for the taxing ordeal of child birth and quick wits for keeping all the big, dumb men in line. And so we have all evolved.

Going off what Surgoshan said, men have more testosterone becuase in our past, man needed more muscles to hunt. So man has evolved more muscle mass and testosterone through time.

Why in some species it is the other way around?

I understand that testosterone makes men stronger. I know that men developed into hunters and needed this ability. I am just wondering why men and women in the human species developed into these roles.

Sure men needed strength to hunt, but why did the first man go out to hunt in the first place? Would women be stronger than men today if it was a woman instead of a man who hunted first?

In hunter gatherer societies, women actually provide most of the food and do most of the labor of preparing it, so that’s not the explanation.

Men (and males in many species) are larger and stronger in order to compete with each other over access to females.

One posibility is that early man thought that there was a connection between fertility and large frames. So the men grew larger to impress the females, and the females in turn chose large men because they were attracted to them. This is the same reason that men are attracted to women with large breasts. Larger breasts are a way for women to show off their fertility, and so men grew to look for them and women grew to produce them. If you want to see an example of this kind of showing-off in action, look at a peacock. It’s kind of like “Look how big I can make my tail without getting eaten”. This isn’t quite the same as a large frame actually adds to one’s natural selection potential, but some particluar trait doesn’t need to be evolutionarly advantageous for it to be selected.

I heard somewhere that humans evolved long hair on their heads because it could be decorated. You’d be surprised how much of us is the way it is because of psychology.

Remember that sexual dimorphism didn’t evolve first in humans. We’ve inherited it from our very ancient mammalian ancestors. Males average bigger and stronger in most mammalian species.

Since females participate in hunting and gathering in a lot of mammalian species, I don’t think the different physical strength can be explained by males going out and hunting while women stay home and care for the kids. But males do fight over access to females in every mammalian species I know of, so I think Cher3 has the right answer in attributing it to sexual competition.

ObDisclaimer: Strength varies wildly; if you put my male behind in the ring with Jackie Joyner Kersee she’ll probably whale the hell out of me, etc.

I’m always really skeptical about these “men are strong because they are hunters” arguments. People hunt by the use of cunning and sharp things, especially sharp things that allow you to keep the heck away from whatever it is you are trying to kill. It’s not like early hunters were leaping on the nearest mastadon and strangling it with their bare hands. It probably took a lot of people working together to kill something like that, and there’s no reason to think that some of them might not have been women.

Women commonly went hunting among the Inuits–people who actually depended mostly on meat as food, unlike hunter/gatherers. They went out on whaling boats and hunted small game themselves. I’ve seen carvings depicting Inuit women hunting and fishing while carrying an infant in a sling on their backs.

And as for the “men work, women take care of the babies” argument, well, women in any traditional society would get a laugh out of that. “Caring for children” didn’t mean sitting around watching Barney, guys, it meant strapping the kid on and getting on with your gathering, cooking, butchering, tanning, weaving, etc.

Mirage, I want to impress girls. Tell me, pretty please, how to grow larger?
And, BTW, why some women have small breasts? Their mothers, by definition, attracted males.

There are a number of theories, actually. The two most commonly accepted are commonly known as the “Man the Hunter Theory” and the “Sexual Selection Theory.”

Man, the Hunter Theory: While rearing young, early hominid females were unable to hunt large game animals as efficiently as males. The males were therefore encouraged to undertake the inherently perilous task of hunting, while the females both reared the offspring and gathered less belligerent foodstuffs. This sexual division of labor selected stronger, more durable men, who were less likely to have their (thicker) skulls crushed and their (more massive) limbs snapped off by a mastodon. In a possible secondary benefit, the (presumably) stronger males who managed to not be flattened and returned with food would possibly tend to feed their own offspring first, thus giving their own genetic material a better chance of survival.

Sexual Selection Theory: Female selection of a reproductive partner, coupled with male-male competition for access to breeding partners led to physical confrontation between males. The stronger males (or those perceived to be stronger) won the access to breed with one or more females. This sexual competition selected for stronger, more durable males who were more likely to win physical battles with other males and still be able to mate afterwards.

The truth probably comes in somewhere in the middle of the two theories and they are certainly not mutually exclusive. Nor, of course, are they the only two. The Sexual Selective Theory seems to be the operative in the sexual dimorphism of other (Non-Human) primates, however, so the Hunter Theory has had some vociferous opposition among primatologists.

Also, keep in mind that the question is a bit misleading, as stated. Female humans are more than strong enough to accomplish the same tasks as male humans, as a rule. The question is: “Why are males excessively strong” not “Why are females weak”
(I know the OP is phrased correctly, but I don’t want anyone to think ‘weaker’ implied ‘weak’)
This site Here has, as a start, an extensive bibliography in addition to a brief discussion of the matter.

Thank you, and Goodnight.

Pregnancy consumes body resources. The sum total of resources that must be consumed in order to maintain a pregnancy can be thought of as

catabolism(self)+catabolism(embryo)+anabolism(self)+anabolism(embryo)

where catabolism is the process of manufacturing new cells to replenish old ones, build up and maintain body tissue and whatnot, and anabolism is the process of doing general chores such as walking, running, carring infants, cooking, spearing antelope, and so forth.

If we assume that resources are sometimes in scarce supply, anything that can reduce one of the elements in the formula means an ability to get by with fewer resources consumed.

Anabolism(embryo) is pretty low to begin with; catabolism(embryo) can’t really be messed with (if you’re gonna construct an infant you gotta deploy the resources); that leaves anabolism(self) and catabolism(self). One cool way of reducing both by quite a bit in one easy whack is to reduce total body mass. Of course, the resulting body still has to be functional for the mom-person who still has those anabolic chores to do, and if the reduction in size adds significantly to overall vulnerability, that’s not good either, as becoming prey is not a good survival strategy. OK, let’s suppose we retain long legs, strong for running and carrying, and concentrate the size reductions in the thoracic section of the body. We’ll also dump fewer resources into the arms and make do with smaller muscle mass there, since the need for full strength in that part of the body is somewhat rarefied. Hmm, perhaps up the body fat content to retain heat and further lower anabolic costs.

Again, who knows why these graceful theoris do not work in many species?

Basically, what Jingo said:

Women are about as big as human beings need to be. Men are larger than this because they need to kick other guys’ asses. The bigger guy wins.

But, since humans are only mildly polygynous (mostly monogamous, with a few rare harems), that sort of competition doesn’t always come into play, and is offset by the detriments of being larger: need more food to survive, greater strain on heart, etc. So guys are a little bit larger, but not taht much larger (as compared to say, male and female sea lions).

You missed what Danimal said:

Males being bigger isn’t a function of anything we’ve been doing for the last 25,000 years. It’s a function of what we were doing when we looked like Zimbu the Monkey.

Who the heck said this?

peace, the reason some species are different is usually because they don’t have the same advantage to be hand in dividing labour between two pair-bonded adults. There’s an obvious advantage to the male hunting and the woman gathering, so males had to develop larger lungs and chests, and got bigger accordingly. In a species where males and females don’t cooperate in raising families, there’s no reason for that distinction to have arisen.

As to your question why some women have small breasts - well, the truth is, very few women have small breasts, relatively speaking. Humans are one of the few mammals where the female prominently displays protruding breasts even when not nursing. In other words, an A cup is more than most mammals have. Besides, if all women were exactly the same height and body mass and none of them had implants, you’d be shocked how much less variance there’d be in breast size.

Peace asked why it was the other way around in some species. Other people can help me out on this, but I recall reading somewhere that in MOST species, if there is any difference at all (and there often isn’t), females are larger. This seems surprising until you realize that we’re talking mostly insects and reptiles here. However, the argument that I remember is that the only reason for males being larger is competition with other males.

As I recall, one of Desmond Morris’ theories is that women who were smaller than the men helped to trigger the basic parental instinct to protect small weak children, into giving extra protection to smaller women.

My Anthro Prof in college agreed with the body mass theory. In a true hunter society with primitave tools, the hunters needed enough muscle mass to take down the game. But because of the down time in the latter stages of the long mammalian pregnancy, a woman with lots of extra muscle and body mass would require lots of food, without contributing to the hunt, and increase the chances starvation within the group.

[QUOTE]
*Originally posted by RickJay *

Who the heck said this?

Tymp said it, among others.

Also, RickJay, I don’t dispute that humans inherited dimorphism from their ancestors. I dispute the idea that males became larger due to selection pressures involving hunting. Males are larger in most mammalian species, but they don’t provide the food in most mammalian species. Females either get the food themselves (e.g., grazing species and gathering species), or participate at least equally in hunting (e.g., wolves, lions and other hunters.)