In early 2010 I wrote in a note that one's political persuasion (liberal v conservative) may be determined by dna as opposed to rational thought processes and environmental factors (family, friends, classes taken in college, etc)  I've attached that note for reference.  My basis of thought was then & still is that the statistical inferences for a roughly 50:50 split between liberal and conservative voting in all cultures through-out time seems to go well beyond an environmental basis for the split, and that therefore it would have to be due to a human genetic trait, more likely having to do with more/less fear of unknowns.... something in our human evolutionary condition that supports survival. 

 

Excerpts from that note:

The US population, as diverse as it is having grown over time from different batches of immigrants with differing cultural back-grounds, gene pools, etc. continues to split nearly down the middle in political elections... give or take some small delta.  On average it's a 50:50 split.  Is there thus some physical reason for why the population is divided thus... i.e. a dna related split in the human genome pool that gives half the population a preponderance for conservative ideals, and the other half a preponderance for progressive ideals?

 

What makes a person dominantly analytic and others dominantly emotional in their natures?   How much of this is influenced by environment and how much by dna? 

 

In other words, is there a predisposition in human nature to prefer the conservative or progressive nature of human discourse. ... such that real logic is only peripherally related to how they actually vote. 

 

"According to an emerging idea, political positions are substantially determined by biology and can be stubbornly resistant to reason. 'These views are deep-seated and built into our brains. Trying to persuade someone not to be liberal is like trying to persuade someone not to have brown eyes. We have to rethink persuasion,' says John Alford, a political scientist at Rice University in Houston, Texas... [O]pinions on a long list of issues, from religion in schools to nuclear power and gay rights, have a substantial genetic component. The decision to vote rather than stay at home on election day may also be linked to genes. Neuroscientists have also got in on the act, showing that liberals and conservatives have different patterns of brain activity."

In 2003, John Jost, a psychologist at New York University, and colleagues surveyed 88 studies, involving more than 20,000 people in 12 countries, that looked for a correlation between personality traits and political orientation (American Psychologist, vol 61, p 651). Some traits are obviously going to be linked to politics, such as xenophobia being connected with the far right. However, Jost uncovered many more intriguing connections. People who scored highly on a scale measuring fear of death, for example, were almost four times more likely to hold conservative views. Dogmatic types were also more conservative, while those who expressed interest in new experiences tended to be liberals. Jost's review also noted research showing that conservatives prefer simple and unambiguous paintings, poems and songs.

...A much stronger link exists between political orientation and openness, which psychologists define as including traits such as an ability to accept new ideas, a tolerance for ambiguity and an interest in different cultures. When these traits are combined, people with high openness scores turn out to be almost twice as likely to be liberals.

Combine the genetic influences on personality with the political tendencies of different personality types, and the idea that genetics shapes political tendencies seems very plausible indeed. All of the big five personality traits are highly heritable (Journal of Research in Personality, vol 32, p 431), with several studies suggesting that around half of the variation in openness scores is a result of genetic differences. Some traits that are linked to openness, such as being sociable, are also known to be influenced by the levels of neurotransmitters in the brain. And levels of these chemicals are controlled in part by genes. So while there isn't a gene for liking hippies, there is probably a set of genes that influences openness, which in turn may influence political orientation.

A study at University College London in the UK has found that conservatives' brains have larger amygdalas than the brains of liberals. Amygdalas are responsible for fear and other "primitive" emotions. At the same time, conservatives' brains were also found to have a smaller anterior cingulate -- the part of the brain responsible for courage and optimism. 

"It is very significant because it does suggest there is something about political attitudes that are either encoded in our brain structure through our experience or that our brain structure in some way determines or results in our political attitudes," Geraint Rees, the neurologist who carried out the study, told the media.

 

Rees, who heads up UCL's Institute of Cognitive Neuroscience, ... ...after studying 90 UCL students and two British parliamentarians, the neurologist was shocked to discover a clear correlation between the size of certain brain parts and political views.

 

He cautions that, because the study was carried out only on adults, there is no way to tell what came first -- the brain differences or the political opinions.

In a study published in October, researchers at Harvard and UC-San Diego found that a variant of the DRD4 gene predisposes people to being liberal, but only if they had active social lives as adolescents. The "liberal gene" has also been linked to a desire to try new things, and other "personality traits related to political liberalism."

Fowler concludes that the social and institutional environment cannot entirely explain a person's political attitudes and beliefs and that the role of genes must be taken into account. "These findings suggest that political affiliation is not based solely on the kind of social environment people experience," said Fowler, professor of political science and medical genetics at UC San Diego.

 

We speculate that the association of gray matter volume of the amygdala and anterior cingulate cortex with political attitudes that we observed may re?ect emotional and cognitive traits of individuals that in?uence their inclination to certain political orientations.

For example, our ?ndings are consistent with the proposal that political orientation is associated with psychological processes for managing fear and uncertainty. The amygdala has many functions, including fear processing. Individuals with a large amygdala are more sensitive to fear, which, taken together with our ?ndings, might suggest the testable hypothesis that individuals with larger amygdala are more inclined to integrate conservative views into their belief system?. Similarly, it is striking that conservatives are more sensitive to disgust, and the insula is involved in the feeling of disgust.

On the other hand, our ?nding of an association between anterior cingulate cortex volume and political attitudes may be linked with tolerance to uncertainty. One of the functions of the anterior cingulate cortex is to monitor uncertainty and con?icts. Thus, it is conceivable that individuals with a larger ACC have a higher capacity to tolerate uncertainty and con?icts, allowing them to accept more liberal views. Such speculations provide a basis for theorizing about the psychological constructs (and their neural substrates) underlying political attitudes. However, it should be noted that every brain region, including those identi?ed here, invariably participates in multiple psychological processes. It is therefore not possible to unambiguously infer from involvement of a particular brain area that a particular psychological process must be involved.