[...] The researchers found that most people in countries widely described as collectivist have a specific mutation within a gene regulating the transport of serotonin, a neurochemical known to profoundly affect mood.Culture (Not Just Genes) Drives Evolution: Cultural differences have manifested themselves in the DNA of distinct, regional populations. (Discovery News)
In China and other east Asian nations, for example, up to 80 percent of the population carry this so-called "short" allele, or variant, of a stretch of DNA known as 5-HTTLPR.
Earlier research has shown the S allele to be strongly linked with a range of negative emotions, including anxiety and depression. Critically, it is also associated with the impulse to stay out of harm's way. By contrast, in countries of European origin that prize self-expression and the pursuit of individual over group goals, the long or "L" allele dominates, with only 40 percent of people carrying the "S" variant.
Setting aside discredited ideas linking genetics and race, the researchers suggest that culture and genes may have interacted over time to shape the process of natural selection, helping individuals -- and the societies in which they lived -- to survive and thrive.
Ancient cultures in Asia, Africa and Latin America highly exposed to deadly pathogens, they conjecture, may have tended toward collectivist norms in order to better combat disease. That social transformation, in turn, could have favored the gradual dominance of the risk-avoidance S allele.
Setting aside discredited ideas linking genetics and race, the researchers suggest that culture and genes may have interacted over time to shape the process of natural selection, helping individuals -- and the societies in which they lived -- to survive and thrive. Ancient cultures in Asia, Africa and Latin America highly exposed to deadly pathogens, they conjecture, may have tended toward collectivist norms in order to better combat disease.
"We demonstrate that evolution is operating at least two levels," said Joan Chiao, a professor at Northwestern University in Chicago and lead author of the study. "One is biological, which is well understood. But there is also a level where cultural traits may have been selected for themselves, emerging in congruence with the selection of different types of genes," she explained by phone.
One well known example of so-called "culture-gene co-evolutionary theory" has to do with drinking cow's milk, something humans are not intrinsically adapted to do. Over time, milk consumption led to both the genetic selection of protein genes in cattle, and a gene in humans that encodes lactase, an enzyme that can break down the otherwise indigestible lactose in dairy.
In the case of collective cultures and the S allele, "we don't make a strong claim on the chicken-or-egg problem" of which came first, said Chiao. "What we are proposing is that cultural and genetic selection actually operate in tandem, and that you can view human behavior as a product of culture-gene co-evolution," she said.
The study also argues that collectivist cultures may help protect against the genetic risk of depression that comes with having the S allele.
"Such support seems to buffer vulnerable individuals from the environmental risks or stressors that serve as triggers to depressive episodes," said Chiao. The fact that the United States and Europe have higher rates of anxiety and mood disorders despite having the L allele may come from the stress of living in highly individualistic cultures, she suggested.
Note that as the collectivist nature of Asian societies is being torn apart in the desire to "Westernize," rampant mental illness and societal follow as night follows the day. However, the high Japanese rate of suicide seems to be an anomaly in the study's conclusions.