Why do people have sex? Prima facie, that question is a no-brainer. It feels good. It’s fun. We like it, a lot! And so, we pursue it and do it, as often as possible. Sex is, arguably, humankind’s most common and immediate form of pleasure and entertainment. As Mark Twain said, “To the lonely it is company; to the forsaken it is a friend; to the aged and impotent it is a benefactor; they that be penniless are still rich, in that they have this majestic diversion.”