Often in the past, and even today, sex has been used to humiliate the other. When an army would win over a country, then to stamp its authority, the soldiers would go and rape the women in the newly won territory. It was to show to them that “Now we are your masters”. That is one use of sex—to show to the other that “I have control over you”.
Genghis Khan went on winning more and more territory, and wherever he won, he raped. That was his way of showing that he was the winner. “Now I can have control over your body, just as I have control over your territory.” He raped so many women that almost 10% or 15% of the people in Asia carry his genes—because he was a big winner.