The response of some people to reading the headline will be, “duh!”
The above reaction probably explains why this phenomenon hasn’t been studied that much. But it’s worthy of study because, as far as I know, it’s the greatest example of sexual dimorphism in humans.
There is a lot of negative reaction from female readers at the suggestion that they might be 4/15 of a standard deviation less intelligent than men. But women don’t seem to mind at all that they are 2 SD shorter than men and, as far as my best guess goes, 3 SD weaker than men.
A 3 SD difference means that a very weak man would be weaker than a very strong women, but if men and women were paired off randomly it would be pretty rare for the man to be the weaker member of the couple. It would be a lot rarer than the woman being taller than the man because there is only a 2 SD height difference. A man of average strength may never encounter a woman who is stronger than him, unless he happens to bump into a female bodybuilder who cheats by taking anabolic steroids (drugs that reproduce the muscle-building effect of testosterone but are supposed to have fewer masculinizing side effects). Even female bodybuilders on steroids are not as strong as male bodybuilders, so there is more to the male-female strength difference than just testosterone.
As mentioned before at this blog, there is a significant difference in math ability between men and women (perhaps half an SD), but the difference doesn’t show up until puberty. The same is true of strength differences. The average prepubescent boy is only slightly stronger than the average girl of the same age, and because girls enter puberty about two years earlier than boys, there is a brief span at around the age of 12 to 13 or so when the average girl is actually stronger than the average boy. But then, just as boys pull ahead in math ability, they pull way ahead in physical strength.
The difference in math ability causes great envy among some feminist types, and this attitude has mostly gone mainstream. The typical modern woman will get very mad at you if you point out that men are better at math because they are men. But women don’t want to be strong like men. The ideal body type for women is to be skinny which gives off the appearance of weakness. The higher up the social class ladder you go, the more emphasis women will place on being thin. Most women don’t want to lift weights because they don’t want to be stronger. The most popular exercise activity for women in Manhattan seems to be running, which tends to make women look gaunt and less strong-looking.
Women generally like their men to be strong, and it’s common to hear the rationalization of “strong men make me feel safe.” But statistically speaking, a woman’s boyfriend or husband is far more likely to beat her up than anyone else. During the time of my brief internship at the city prosecutor’s office in Phoenix, I saw a whole bunch of men being tried for beating up their girlfriends or wives. Women would be a lot safer partnered with a weak man who couldn’t beat her up.
Is it any different in Japan. According to that NY Times article:
[T]he new Japanese woman, according to the fashion critic Ikuko Hirayama, is: "strong, robust, bursting with energy. She takes care of her body but is not obsessed with being thin. She's proud of her biceps and also proud of her sexuality."
And then later in the article, that role reversal couple:
Both Shirakawa and his girlfriend like the fact that she weighs more than he does, and is the leader of the couple. "She's a lot stronger than I am, can lift heavy things and go drinking until dawn. I admire that about her, and feel protected when I'm around her," he said.
People generally think this article is bogus and the reporter made most of it up. Most Asian women I see look pretty thin and weak to my eyes, but I haven’t been to Japan—maybe Japan is full of strong robust women showing off their biceps, but somehow I doubt it.
What are the evolutionary pressures which caused men to get so much stronger than women? Sure, we assume that muscles helped men fight other men for women, and helped men when they went out hunting, but why didn’t women also get stronger? Wouldn’t strength also be beneficial for women who often had to gather food for herself and her children? There must be something negative for women about being strong. Maybe muscles are detrimental to overall health? Women tend to live longer than men. Do big muscles lower one’s life expectancy? The least muscular race, Asians, have the longest life expectancy, and the most muscular race, blacks, have the shortest life expectancy.