October 29, 2009

Coevolution of individualism–collectivism and the serotonin transporter gene

From the paper:
Here, we demonstrate for the first time a robust association between cultural values of individualism–collectivism and allelic frequency of the serotonin transporter gene, controlling for associated economic and disease factors. Geographical regions characterized by cultural collectivism exhibit a greater prevalence of S allele carriers of the serotonin transporter gene, even when cultural regions rather than nations served as the unit of analysis. Additionally, we show that global variability in historical pathogen prevalence predicts global variability in individualism–collectivism owing to genetic selection of the S allele of the serotonin transporter gene in regions characterized by high collectivism. Importantly, we also reveal a novel and surprising negative association between individualism–collectivism, frequency of S allele carriers of the serotonin transporter gene and global prevalence of anxiety and mood disorder. Across nations, both collectivism and allelic frequency of the S allele negatively predict global prevalence of anxiety and mood disorders. Critically, our results further indicate that greater population frequency of S allele carriers is associated with decreased prevalence of anxiety and mood disorders due to increased cultural collectivism.

The current findings suggest a novel demonstration of culture–gene coevolution of human behaviour. Emphasizing social norms that increase social harmony and encourage giving social support to others, collectivism serves an ‘anti-psychopathology’ function by creating an ecological niche that lowers the prevalence of chronic life stress, protecting genetically susceptible individuals from environmental pathogens known to trigger negative emotion and psychopathology. These findings complement notions that cultural values of individualism and collectivism are adaptive and by-products of evolution, more broadly. For instance, recent evidence suggests that cultural values of collectivism also serve an ‘anti-pathogen defence’ whereby behavioural manifestations of collectivism, such as conformity and parochialism, function as buffers against the transmission and increased prevalence of disease-causing pathogens (e.g. malaria, typhus and tuberculosis) (Fincher et al. 2008). Our results provide novel evidence that geographical regions characterized by collectivistic cultural norms have a higher historical and contemporary prevalence of infectious diseases due, at least partially, to genetic selection of S allele carriers (Fincher et al. 2008). Taken together, these findings dovetail nicely as two examples of how cultural values serve adaptive functions by tuning societal behaviour so that social and environmental risk factors are reduced and physical and mental health of group members is maintained. Importantly, in the current study, we found that population frequency of the serotonin transporter gene was a singular predictor of cultural values of individualism–collectivism across nations, even when controlling for historical and contemporary pathogen prevalence. Hence, our findings illustrate that gene frequency plays a unique role in explaining global variation in the adoption of cultural norms and is fundamental to any comprehensive understanding of culture.

Proceedings of the Royal Society B doi:10.1098/rspb.2009.1650

Culture–gene coevolution of individualism–collectivism and the serotonin transporter gene

Joan Y. Chiao, and Katherine D. Blizinsky

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.



TwoYaks said...

While I'm usually quite favourable to these sorts of hypotheses, it seems like they could have plunked any gene with similar clinal variation due to population structure and got the same result. I'm unconvinced.

Would they argue that changes in the incidence of collectivism/individualism within a country would be driven by changes in allelic frequency?

Unknown said...

Can you cite another example of a gene with similar clinical variation due to population structure, though? Or is this simply conjecture?

Maju said...

Essentially it's a vertical identity: the allele frequency does not really vary in all Western countries, in spite of such huge differences in "collectivist" tendencies (10-70%). Only the middle Eastern Asian bloc (remember that Singapore is mainly ethnic Chinese) shows some homogeneity but even among them Japan is clearly outside of the pattern, with a collectivist score of only slightly above 50%.

Looks something more cultural than properly genetic, at least on light of this paper. The gene is distributed along ethnic lines and may have some correlation with the other pattern... but only a very rough, diffuse one. It can't be the only causant of the socio-political differences, which are largely independent.

Unknown said...

(1) I would be interested to know how they objectively quantified the "individualism - collectivism" axis.
(2) Maju is correct: the distribution is essentially vertical. Furthermore, data points from east asia have high leverage, so would potentially skew the conclusion.
(3) having lived in China, I am not surprised at the allegation that people in that country are "calm". Imagine a 4-lane highway with 6 lines of traffic, with cars cutting each other off arbitrarily... and NO road rage. Imagine a city street filled with so many pedestrians that it looks like a crowded mall during the christmas shopping season, with people shoving each other aside... and NO outrage. I often wondered whether such tolerance was culturally-instilled or had a genetic basis. A genetic explanation seems plausible, especially because the Chinese system of collective labor extends far further back than the Communist revolution. (Some say it's based on the need for collective work to construct rice paddies, which are not simple engineering tasks that can be completed by a single laborer.) On the other hand, if you grow up in such a crowded society (in which the concept of personal space is alien), you certainly need to adapt to it.

Unknown said...

Here's the full study if anyone's interested:

Maju said...

WTF!, it's open access.

Jack said...

France and Italy have a relatively large number of people voting for various communist parties (10% each more or less). They are state centered countries with a corporativist mentality.
How they ended up so low in collectivism is something that makes me wonder.

szopen said...

Jack, exactly - and Poland, which is dubbed frequently "pathological individualists country" ...