What was behind the evolution of human brain? Hello @Achmed, and welcome to the site. Could you clarify your question some? As is, the question is rather vague. Is there some aspect of human brain evolution that you want to understand? The vertebrate brain goes back ~550 million years, so the human brain is just one in a long series of brains. It's not clear what you mean by "selective evolution." Is there reason to think that natural selection doesn't act on the brain?