Wednesday, October 28, 2009

Germs, collectivism and serotonin   posted by Razib @ 10/28/2009 01:38:00 PM

Culture-gene coevolution of individualism-collectivism and the serotonin transporter gene:
Culture-gene coevolutionary theory posits that cultural values have evolved, are adaptive and influence the social and physical environments under which genetic selection operates. Here, we examined the association between cultural values of individualism-collectivism and allelic frequency of the serotonin transporter functional polymorphism (5-HTTLPR) as well as the role this culture-gene association may play in explaining global variability in prevalence of pathogens and affective disorders. We found evidence that collectivistic cultures were significantly more likely to comprise individuals carrying the short (S) allele of the 5-HTTLPR across 29 nations. Results further show that historical pathogen prevalence predicts cultural variability in individualism–collectivism owing to genetic selection of the S allele. Additionally, cultural values and frequency of S allele carriers negatively predict global prevalence of anxiety and mood disorder. Finally, mediation analyses further indicate that increased frequency of S allele carriers predicted decreased anxiety and mood disorder prevalence owing to increased collectivistic cultural values. Taken together, our findings suggest culture-gene coevolution between allelic frequency of 5-HTTLPR and cultural values of individualism-collectivism and support the notion that cultural values buffer genetically susceptible populations from increased prevalence of affective disorders. Implications of the current findings for understanding culture-gene coevolution of human brain and behaviour as well as how this coevolutionary process may contribute to global variation in pathogen prevalence and epidemiology of affective disorders, such as anxiety and depression, are discussed.

Here's what I see going on:

High pre-modern pathogen load → collectivist values → S allele & dampening of psychological responses associated with S allele in populations where it is extant at lower frequencies.

It's Open Access so you can look at their regressions yourself. The association with pre-modern levels of pathogens is a strong point for me, these sorts of biological factors would result in a consistent "push" over long periods of times which culture itself might not have. The agricultural civilizations of Asia were always going to be rich ecologies for infectious diseases. So it would be interesting to look at the frequencies of the S & L alleles on a finer scale; for example, in the islands of Japan. Though that case I suspect that lower-density areas would have had so much migration that selection wouldn't have time to maintain different allele frequencies.