There was an academic who investigated psychopathy. He performed a study in which he himself was one of the subjects, and when the results of brain scans arrived, he noted one of the scans was obviously psychopathic. He placed it on a pile of others he had noted and continued until he realized that his scan was not among the others. He searched through the stack and found that the obviously psychopathic subject was, of course, his. He explained that he had never killed anyone, never contemplated such a thing. He was no thief; he was married and responsible. He told this amusing anecdote in order to show how there are high-functioning psychopaths among us.
It is the case that such an evolutionary advantage may be quite valuable, if civilization were to take a turn for the worse when, say, climate changes affect the tightly-knit human universe. Climate change could transform humanity into a race of mostly psychopaths.