Serial killers have no empathy for their victims. They seem to get a high from the killing of others. Maybe it is a power thing.
They (psychologists) have another name for it that is escaping me at the moment.
Psychopathy is marked by several behaviors or traits, including extreme narcissism, rage as the result of thwarted personal goals, duplicity, treating individuals as means to ends, deadened response to normal stimuli and a distinct and utter lack of empathy.
BTW, evolution is accurate, much of our own human behavior finds a more primitive analog in chimpanzee societies. The difference is that human beings are beings of reason as well as instinct. If we weren’t a part of everything else, how is it that we are sexually dimorphic creatures like others of that type and have the urge to mate in such a similar fashion, that we excrete waste and eat just as other species do. Only reason separates us, and with very low-IQ people (or babies and small children) even that faculty is much weaker and the individual resembles an intelligent animal to a great extent.
One need only sit down to read the great philosophers to know that we are different from animals and how, yet not forsaking the truth that we ARE related to them.