well legitimate skeletal/mass structure between women and men are why pro sports stay segregated, unlike high school sports, like wrestling, which are well known in being unisex, allowing male wrestlers and female wrestlers to compete against one another. Ronda Jean Rousey and Miesha Tate can kick most mens' ass, but in the context of the UFC, male UFC figthers aren't the average man. based on skeletal structure and mass displacement, a male fighter of the same weight class as Rousey is going to deliver a lot more force than what Rousey could deliver. this is why male versus female fighting will probably never happen. while weighing the same and having the same skills might make a male and female fighter even on paper, it'd be unfair in the sense that the male biology is designed differently form the of the female biology, causing an unfair advantage. that isn't to say that in reality Rousey couldn't destroy another male fighter in her weight-class because she can.