“Biology has long struggled with the concept of altruism. There is now reasonable agreement that its purpose is partly to be nice to relatives (with whom one shares genes) and partly to permit the exchanging of favours. But how the brain goes about being altruistic is unknown. Dr Marsh therefore wondered if the brains of extreme altruists might have observable differences from other brains—and, in particular, whether such differences might be the obverse of those seen in psychopaths…
“Their conclusion is that extreme altruists are at one end of a ‘caring continuum’ which exists in human populations—a continuum that has psychopaths at the other end…
“Some biologists regard psychopathy as adaptive… Dr Marsh’s work suggests that what is going on is more like the way human height varies. Being tall is not a specific adaptation (though lots of research suggests tall people do better, in many ways, than short people do). Rather, tall people (and also short people) are outliers caused by unusual combinations of the many genes that govern height. If Dr Marsh is correct, psychopaths and extreme altruists may be the result of similar, rare combinations of genes underpinning the more normal human propensity to be moderately altruistic.” (The Economist – subscribers only)
It may indeed be random variation. But you also have to explain why ‘bad genes’ do not get eliminated. Another unconnected piece of research gives a clue:
“They were looking for evidence that linked trolling with the Dark Tetrad of personality: narcissism, Machiavellianism, psychopathy, and sadistic personality.” (Psychology Today)
And found it, naturally enough. But what I found more interesting was that “debaters” – people who make serious contributions – scored slightly above average for all of these qualities except narcissism, where they were marginally below average. People who favoured chatting were average except for narcissism, where they averaged above average, naturally. “Non-Commentators” were below average on all counts.
This suggests to me that bad qualities may be overdoses of things that can be positive in small amounts. Maybe we’d be better off if we could curb the extremes, but we can’t entirely do without those things. And if there were multiple genes involved – as there are for height – then the random sorting of genes would produce unwanted extremes.
Say there were ten independent genes each tending towards psychopathy: getting just three or four might make a strong and confident character who was still moral and considerate. Ten genes for narcissism might mean three or four make for someone chatty who usefully passes on news, but is not unduly self-obsessed.
Other studies have shown that psychopathic types are found disproportionately in business and finance. (The Guardian). A good reason to regulate them – and in practice. only state regulation will actually curb such characters.