On the flip side, self-control, impulse control, being able to manage your emotions with a toolbox: these are skills that are learned, honed, and mastered. Sure, many people learn them through other means than from their parents, often as a survival necessity in their environments, but I don't think that e.g. the people who fly off the handle and get into a bar fight when someone's hitting on their girlfriend, are doing so because of heavy metal poisoning or genetics.