Culture and Genes working together

Cultural differences have manifested themselves in the DNA of distinct, regional populations.

According to a study in the Proceedings of the Royal Society B: Biological Sciences Journal released in October, 2009, both culture and genes drive evolutionary outcomes. The study compared individualistic and collectivist societies around the world. It looked at the interplay of two sets of data, one genetic and the other cultural across 29 countries. The researchers found that most people in collectivist societies have a specific mutation within a gene regulating the transport of serotonin, a neurochemical which profoundly affects mood. In China and other east Asian nations up to 80 of the population carries this ‘short’ allele or variant of a portion of DNA known as 5-HTTLPR. This allele is strongly linked with a range of negative emotion states like anxiety, depression and the tendency to stay out of harm’s way (risk aversion). Collectivist cultures help to buffer individuals from these emotional difficulties with support systems. "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.



The study suggests that together culture and genes may have interacted to shape the process of natural selection tailoring the individuals helping them to fit in the societies into which they were born. Some societies banded together toward collectivist norms to stave off threats like disease while others took a more individualistic approach.

"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."

One good example of the “culture-gene co-evolutionary theory” explains lactose intolerance. Over time, milk consumption led to both the genetic selection of protein genes in cattle and a gene in humans that encodes lactase the protein that breaks down the lactose in dairy. Cultures which drank milk have more members with the ability to digest it.