In previous entries, I have explored the idea that good and evil are both part of the human brain; in particular, there is genetic variability for the impulses that underlie goodness (e.g., altruism) and evil (e.g., psychopathic violence) in human populations. Natural selection may favor altruism in some demes, and violence in other demes, of the same population at the same time.
I have one further speculation to make. Ever since scientists began to discover that the things that people think, feel, and do are determined in large measure by brain chemistry and structure, and the genes that underlie them, the idea of free will has come under attack. How can the people we call evil be held accountable for their actions, if their actions result inevitably from the interaction of their genes and their environments? This may not be an important question, since humans help to create their own environments, and since we have to control evil people even if they are not spiritually culpable. But modern brain science discoveries do raise an important question: what about free will?
Every human behavior is an interaction of genes and environment. It is always both. In some people, genetic abnormalities are so severe that their behavior is almost a stereotypical script; for them, genes are more important than environment. For most people, genes influence feelings and attitudes, while environment (including their current capacity to make decisions) is much more important. It is a sliding scale from the overwhelming importance of genes to the overwhelming importance of environment.
Perhaps the same thing is true of free will. It is perhaps nonsensical to ask whether humans have free will or not. All humans have free will, but some humans have very little of it, while most of us have a great deal of it. It, too, may be a sliding scale.
I propose this possibility for your consideration. Please comment on it if you like.