I'm a bit disappointed that I haven't seen anyone point out what I see as obvious. At just about any age group, introducing girls to a male dominated game changes the psychological dynamics.
What happens when a guy loses to a girl? He is roundly ridiculed for losing to a girl. What if he wins? No one cares, he beat someone who is stereotypically weaker. There is no win scenario for a guy facing a girl. Not to mention the "white knight" complex, where you have some guys going out of their way to help out the female player, even to the detriment of their overall team cohesion and strategy. Also, you have a natural inclination for guys to be less competitive against a girl, and if it's a contact sport they are less likely to be as rough as they would be towards another guy.
It's not a simple matter of strength or skill. A female player changes the entire psychological dynamic of the game, and that's not a small change in highly competitive scenarios.
You are so right. This is a much more complicated issue than I could even fully address in this one article. The psychological impact could be very big.
After 3-4 generations of mixed teams people wont be able to comprehend this concept anymore.
No one will be ridiculed for losing against the opposite gender, it will simply be ridicule for losing. (no gender issues in the equation)
I understand your opinion, and by all means you are free to hold it, but I simply don't believe such gender differences can be completely removed. Sure, the overt ridicule might be removed, but the underlying stigma of losing to a girl is not something that can be removed. Similar to how it's hard to remove the stigma of losing to a smaller opponent in a martial arts match, no matter how much rationale you throw at it. It's a "David vs. Goliath" mentality.