When I did my military training in Canada (in the reserves), it was co-ed. The physical part of the training was
easy and I believe that was because of the female component. I remember carrying extra rifles and packs because there were certain females in the platoon who simply couldn't do it. (To be fair, there were a few guys who couldn't cut it either, but those were few and far between b/c it had been so 'gender normed'.) Basically, it was still too hard for the females and what should have been a culling process for eliminating the weaker males was turned into a few months of pep talking so everyone could cross the finish line together.
I remember reading somewhere (maybe in
Quo Vadis, a long time ago) that there were women in Rome who could basically buy the life of a gladiator and kill them after sparring with them. Why this was of any interest, I cannot comprehend, but this thread brought it to mind. (I'm not sure if it was historically accurate.)