@Datun And yes I know men are also victims of other men, but that doesn't seem to make them clasp their keys in their fist across an empty car park, for some reason.
I've been thinking more about why women seem to have this visceral fear response to men that is stronger even than the reaction of smaller, more feminine men to other men. Besides the obviously much lower chance of defending ourselves due to significantly less upper body strength, there is one thing that can ONLY be inflicted by a man on a woman, and that is pregnancy.
Our heightened sense of danger in those situations could have evolved partly due to our evolving reproductive strategy as the female of the species.
Pregnancy, childbirth, and child rearing is enormously costly for female mammals in terms of bodily energy, resources, and risk. There would have been strong pressure to develop instincts that would help us control when, and with whom, we procreate. Obviously we didn’t have things like birth control or access to abortion when we were developing as a species, so the only way for women to control their own reproductive life was to avoid rape at all costs.
This could be why we are so much more tuned into the dangers of men than other men are, even though they are also at risk of violence. Our Spidey senses are more alert because we’re instinctively protecting not only our safety but also our reproductive autonomy.
And when it comes down to it, single-sex spaces, especially where we undress, could be thought of as part of that protection. Anything that decreases our chances of being raped increases our ability to control when we get pregnant.
Someone posted earlier about that study that found something like 90% of rapes occurring in changing rooms happen in mixed-sex changing rooms. I mean, duh, right? Of course they do! So in addition to the many other reasons to have single-sex spaces, it can be argued that they also serve to help us control our own reproductive lives.
Forcing us to pretend we can’t recognize the type of human that can get us pregnant and then forcing us to accept those humans into places where we are vulnerable increases the chances we end up impregnated against our will.
Obviously, once we're past childbearing age, that risk goes away, but the beneficial fear instinct would still be there because that's how evolutionary traits work.