At least, that's how I chose to interpret this report:
An article published in the Journal of Politics looked at 2,000 subjects from the National Longitudinal Study of Adolescent Health, examining their genes, social networks, and political affiliations. What they found was that adolescents who possess a certain variant of the dopamine receptor gene DRD4 were more likely to grow up to be liberal adults. Furthermore, that correlation only existed when adolescents had active social lives.
Remember I was a biophysical inorganic chemist before I was a lawyer, so I know of what I speak on these matters.