Let me tell you about my personal experience with testosterone, which may be of some interest. At the age of 21 I was a junior in college majoring in math and physics, a very thin, effeminate, extremely shy nerd who was sometimes mistaken for a 14 year old prodigy. When I finally saw a doctor and it was found that I produced no natural testosterone, I began giving myself injections of the hormone. Anxious to get results, I often gave myself more than the prescribed dose. The results were profound: Within 6 months I had undergone an accelerated puberty which resulted in a bad case of acne, a much better physique and nearly caused me to flunk out of college. I was often overwhelmed, walking around campus among my peers, by the apish nature of my species. Having lost interest in intellectual pursuits, all I really wanted to do was fight, fuck and pick bananas off of trees. I even began shoplifting for no apparent reason other than it seemed like something I could get away with.

I managed to barely graduate, but my life was thrown into disarray from which I have never fully recovered. It became frighteningly clear to me just how much human lives are controlled by chemicals rather than any moralistic narratives. While a high testosterone level certainly gives you energy, ambition and fearlessness, it probably isn’t very helpful in a technological civilization which requires people to sit at computers all day manipulating symbols. My guess is that women are going to rule in such a world, as high testosterone men become increasingly useless and tend to wind up in prison. It may get to the point where testosterone levels will need to be technologically lowered to reduce crime and make men more socially acceptable.

So understand this, all you LessWrong nerds: when you see someone who is like a thug to you, that he is in the grip of an incredibly powerful mind-altering chemical called testosterone which, more than any other, is responsible for the evil that men do.