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Psychopathy is a term used within Psychiatry and the social sciences to describe individuals who habitually engage in behavior that is antisocial or criminal and without explanation on the basis that the individual suffers from definable mental disorder such as psychosis. Such people it is said do not themselves suffer but cause others to suffer the consequences of their behavior. Although some research suggests that such long-lasting tendencies have the characteristics of a personality dimension other researchers have supported the concept that there is a discrete entity defined by lack of affect and concern for others, inability to anticipate consequences, lack of remorse, egocentricity and inability to learn from experience or form affective bonds. A biological basis is suggested by the effects of some head injuries, marked male predominance, age dependence and the correlates of extra Y chromosomes. The existence of psychopathy poses questions concernng the survival of any relevant genetic predisposition, Whether there are parallels/precursors in the great apes and other primates is a theoretical and empirical issue. How is psychopathy to be defined across species and what observations have been or can be made?
Baroness Wootton, a sociologist and magistrate, summarised her review of the causes of psychopathy in the words that "these are very selfish people and no-one knows what makes them so". But from an evolutionary perspective the problem is why is not every individual purely selfish - in other words the difficulty is to understand the evolution of a moderate degree of altruism or at least co-operativeness in Homo sapiens.
Most individuals in most human societies behave in a co-operative manner with other individuals most of the time. There are times eg wars, civil disarray, when groups of individuals behave with homicidal aggression towards other groups or individuals.Thus while we are a highly socialized species, there are also circumstances in which most individuals will kill others, apparently to survive. What are the genetic bases of these behaviors? Are there individual differences that are genetically determined? Are these species specific?
Observations on chimpanzees in the wild cast light on these questions. Pan troglodytes individuals live in territorial groups with some exchange of females between groups at the time of adolescence. There are interactions between groups, and it is now clear that these sometimes include lethal attacks on members of other groups in defense of territory.
What is particularly interesting is that such behavior is not characteristic of Pan paniscus, the bonobo species that separated from Pan troglodytes 2 million years ago. The species shows a quite different pattern of social and sexual behavior, with greater equality between the sexes and lesser aggression both in hunting and intra-specifically.
It appears that both social and sexual behavior differ qualitatively between species that are closely related to Homo sapiens, and these changes took place on an abrupt evolutionary timescale. The roots of the behavioral difference must therefore be sought in the process that distinguishes species.
It Is plausible there are inter-individual differences within human populations that are genetically determined, but it seems likely that this variation is independent of variation in closely related species.
It seems that inter-individual differences in susceptibility to socialization must arise in relation to the speciation process, and may well be related to sex differences within the species. In other words that sexual dimorphisms are species specific, and they relate to a process of sexual selection that occurs at the time of speciation.
Triarchic Psychopathy Dimensions in Chimpanzees (Pan troglodytes): Investigating Associations with Genetic Variation in the Vasopressin Receptor 1A Gene, , Frontiers in Neuroscience, 2017, Volume 11, p.407, (2017)
Demonic Males: Apes and the Origins of Human Violence, , Boston, p.350, (1996)
Through a Window, , London, p.229, (1990)