And genetics allows for nearly infinite complexity and variation so there is no requirement for two people with similar disposition to have the same moral compass. In fact I'm arguing close to the opposite-- no two people will have exactly the same moral compass, and there is no True North, so to speak.
Studying people with similar deficiencies/anomalies/abnormalities just makes it very clear to see how impossible it is to define anything that is consistent for all mankind, and the "natural law" becomes something more of an amalgam of human traits that are more or less pronounced in different people & populations and occasionally suppressed or re-routed entirely. Are the insane not human if their brains don't process empathy? Does that have theological implications?