Gene-Culture And The Setoronin Transporter Gene

In the penultimate chapter of NOT A CHIMP I try to lay some foundations for a proper bio-social approach to the study of the evolution of human social behaviour through the evolution of several prominent neuro-transmitters. In particular, I reported that the "short" allele of the serotonin transporter gene had been implicated in creative dance in the context of proto-religious collective human mystical experience. I also reported the finding that variability in short, long and extra-long repeat versions of this gene were more prevalent in more demonic societies typified by long-range geographical distribution - like rhesus macaques and humans. Further research has also implicated the short allele of this gene in anxious, depressive and occasionally violent personality traits.

In this interesting open paper in Proceedings of the Royal Society B, Joan Chiao and Katherine Blizinsky fill in another aspect of this growing picture by associating the short allele of the serotonin transporter with gene-culture evolution of collectivistic traits in human society.

As the authors say: "A fundamental way in which culture shapes human behaviour is through self-construal style, or in how people define themselves and their relation to others in their environment. In particular, cultural psychologists have identified two primary styles of self-construal across cultures: individualism and collectivism. Individualistic cultures encourage thinking of people as independent of each other. By contrast, collectivistic cultures endorse thinking of people as highly interconnected to one another. Individualistic cultures emphasize self-expression and pursuit of individuality over group goals, whereas collectivistic cultures favour maintenance of social harmony over assertion of individuality. Self-construal style affects a wide range of human behaviour, including how people feel, think, perceive and reason about people and objects in their environment, and their underlying neural substrates."

However, there is one other important ingredient in the mix - disease. Previous work, they report, has shown that the S allele is selected for in those cultures with great history and contemporary prevalence of disease-causing pathogens like malaria, typhus and leprosy. The S allele appears to be linked with collectivism and the authors posit that a cultural norm of collectivism could help to protect against the run of disease by enhancing conformity and parochialism. It would seem that this would leave many cultures open to affective disorders but in highly collectivized societies, for instance in Asia, this seems not to be the case. Their answer? " Here we propose that by favouring social harmony over individuality, collectivistic cultural norms may have evolved to also serve an adaptive, ‘anti-psychopathology’ function, creating an environmental niche that reduces the risk of exposure to environmental pathogens, such as chronic life stress, for group members. Consistent with a gene-by-environment (GxE) theory of affective disorders, reduced exposure to chronic life stress for individuals living in collectivistic relative to individualistic cultures would then cause reduced prevalence of affective disorders among genetically susceptible individuals. Hence, culture variation in the epidemiological prevalence of anxiety and depression is likely due to geographical variation in the cultural adoption of collectivistic social norms." So, collectivism helps fight disease and protects against the downside of the S allele - affective disorder.