Just as the speck of dust is at the mercy of many forces, so is human behaviour. We are pushed and pulled in all directions by many different biological, cognitive and cultural forces. Some of these may oppose one another, and some may pull in the same direction. It is entirely possible that two instinctual tendencies may act at odds to each other. But that does not mean these forces cannot coexist; it just means that the track through space is more difficult to understand. Just because we have one adaptive mechanism that promotes violence and another that promotes co-operation does not mean that our explanations of these forces are confused. We are pushed one way and pulled another, and our challenge is to try to disentangle the forces and explain their origins.
~ Lord Robert Winston, in Human Instinct: How Our Primeval Impulses Shape Our Modern Lives (2002)