Controlling for other factors (such as size), men only beat women in explosive muscle power. Women have more endurance, and need less rest between sets (when weightlifting). Women's training is hindered by attempts to force them to train like men. The reason that women have smaller skeletons is that they hit puberty earlier than men. Near the end of puberty (I'm talking about the end of development, technically people are fertile before this), males and females both get a surge of estrogen which strengthens the bones and ends the growth of the skeleton. Obesity is more prevalent in females, which can contribute to hitting an early puberty. Sexual abuse also causes early puberty. I also think it's possible that just being sexualized from basically infancy also plays a role, even if a girl is not sexually abused by another person. The fact that estrogen is not filtered out of our water (basically, women on birth control pee it into the water system and we drink it) also plays a role. Women are also discouraged from pursuing athletics and even from playing in a way that they would get any exercise from a young age. Of course, sex-segregated sports are very important, but I just thought I'd tell you this because I felt better (and in some ways, angrier) when I learned it. It's not that women are naturally small and weak, we have been made that way by our environment.