You are to focused on the fruedian theory of life!!! According to Robert Audrey it is not sex, but territory that drives animals and people. In a study they put two groups of baboons on an island and they seperated and each lived in their own territory. Every morning all of them would stand and yell at each other over the borders, but when a female was in heat it was a free for all. Both had enough females and food. A very dominant male took over the one tribe and he started to extend his territory... for nothing else that just that, territory.

As for weapons, man needed weapons to survive, the forming of the weapon forced them to think more... evolving the brain, with a more evolved brain they could form more sophisticated weapons and so the circle continues untill today. Sex is just a basic drive to ensure survival, but it's not the dominant force. Poor and uneducated people have more sex than their higher class counterparts... why is that? The more sophisticated man gets, the more his dirve turns toward money to enlarge his territory.