I wrote an article earlier on this year about the possible evolutionary aspects to psychopathy; the main point being that psychopathy may well have its roots in the hunter-gather instinct in humanity, and that, as a fractional percentile of the overall population, psychopaths, for all their flaws, serve an important function.
Psychopaths may be sexual predators and cynical manipulators, but the author of a recent book ("The Wisdom Of Psychopaths"), Kevin Dutton, makes some excellent points towards a more nuanced understanding of the "disorder".
Dutton's analysis of psychopathy comes from the angle that many of the attributes seen in psychopaths are actually positive for society overall: leadership skills, fearlessness, quick thinking, and heightened perception, for example.
These attributes in isolation allow "socially-adaptive psychopaths" to become the heroes of society: positions of authority and respect like soldiers, policemen, doctors, firemen, and so on. These are people who are drawn to danger like mosquitoes to a flame, and are able to thrive on it, whereas other people would be unable to function, paralysed by fear. They are naturally endowed with the kind of personality attributes that makes them uniquely suitable to roles that require a cool, hard-headed and fast response to a situation. These are the people who are able to make the tough calls necessary that can saves lives.
A "mixing deck" approach
The main thing to consider is that "psychopathy", as Dutton explains, can be seen as a "mixing deck" of a variety of personality attributes. Like when looking at the "Hare Psychopath Checklist", a psychopath doesn't need to have all the attributes fully to qualify; he simply needs to have some combination of these attributes. So a "socially-adaptive psychopath" has the fearlessness and leadership aspects of psychopathy, but not the more anti-social (and obviously destructive) aspects of the disorder. As Dutton points out, it is the more anti-social and less intelligent psychopaths that are the ones you find in prison. So psychopaths can be either heroes or villains (or both!).
And again, "psychopathy" is more a matter of degree. While Hare's psychopathy test says that 30 out of 40 on the list is the "magic number", but it's easier to see the whole thing as a sliding scale of degree. While the average person scores very low on the checklist, the higher up the score, the lower the percentile of the population. So there may still be, say, five or ten percent of the population that could be considered "semi-psychopaths", who might "achieve" a score of more than twenty. Not high enough to alarming, but still considerably higher that average and possibly indicative of anti-social (and criminal) behaviour.
The "love" of the predator
Gong back to the evolutionary explanation, psychopaths therefore have the attributes that make them ideal as hunters.
In many ways, their psychology is that of a hunter. As Dutton mentions, psychopaths have a heightened sense of perception (as successfully shown in psychological experiments). This allows them to spot weakness in "prey": if a person has a low self-esteem, or if a person feels nervous, psychopaths have a heightened perception for the visual signals (body language) that suggest this. A "socially-adapted" psychopath may find a use for this skill as a policeman to spot guilt in suspects, for example; an anti-social psychopath will use this skill to prey on and exploit the vulnerable in society as a con man, for example.
In the modern age, Capitalism has allowed psychopaths an ideal "playground" to flex their muscles and make use of their "skills". Modern globalisation has given psychopaths more freedom than ever before, with the added advantage that their psychology closely matches that of the "pure Capitalist". This explains why psychopaths are disproportionately represented in the board room, and why top companies see them more as an asset than a liability. In this way, modern-day Capitalism is simply an updated version of "the hunt".
The lack of emotions prevalent in psychopaths also brings me on to another aspect of evolution. If psychopaths are incapable of "love", why is "love" so important to humanity?
"Love" is generally equated with empathy and caring for others (which pure psychopaths are biologically incapable of feeling). From a biological point of view, personal relationships may also be nature's way of ensuring the continuation of the species.
"Love" is one thing that separates humans from animals. Animals have sex for procreation, but typically in animals, mothers force their offspring to fend for themselves after a short period. For animals, sex is a purely physical, impulsive act, resulting in short-term empathy between the male and female, and passed on to their offspring for a short time. This can be seen from watching any wildlife documentary about lions, for example.
Humans' brains are designed differently, and are more complex. Consequently, social relationships and sex is more nuanced. We've all experienced "infatuation", and this is generally a typical part of the relationship process. It has been said that emotional "love" fades away in a relationship over time, to be replaced by something more like overall empathy for the partner. There may also be an evolutionary explanation for this, too.
While psychopaths are society's hunters and predators, a more scientific explanation for "infatuation" is that the hormones released at this early stage of the relationship are designed to encourage sex (i.e. procreation). A more scientific use for this in nature is that it ensures that a child is born before emotional "love" (mutual infatuation) fades; the child then acts as a further emotional bond between partners when the partners' mutual infatuation is replaced by a more general respect and empathy for each other and their child (or children).
This also ensures that the child grows up in a healthy parental environment, which is necessary given the long period of human upbringing.
In this way, nature ensures that the species continues.
Psychopaths may also have a sexual role in nature (evolution), too, given that nature needs hunters, leaders, predators and survival skills.
Psychopaths are also nature's survivors, for all their flaws.