Most fighting in nature between birds or between mammals, is not about beating or eating the other person. It is about making him stop fighting while not getting yourself hurt. So when humans fight, they seldom get seriously hurt, and rarely killed. This reduces the chances of either victor or victim geting hurt or killed, and it reduces the loss to the community. Instead of one or both getting killed, both remain alive to fight enemies of the community.
Now, only a stupid animal will winningly fight someone who is more frightening than he is, because he then usually will get hurt or beaten. So one of the things that the not-so-stupid animals do is to look as frightening as possible, and sound frightening too. So fighting cats scream loudly to sound fierce, and turn themselves sideways with their tails fluffed out to look big. Men lean forward and pout their lips and bow their arms to look big and fierce, and shout to sound big and fierce.
Ok? OOHH KKKAYYY???
