Fascinating article from the American Political Science Ass'n. detailing findings suggesting this may be the case. Unexplained: those who change their political affiliation after years of an earlier, adverse one.

"The authors conclude by outlining how their findings can be of use in analyzing the political divisions that characterize virtually all political systems--including that of the U.S. They identify two broad possible genetic phenotypes: the "absolutist" and the "contextual," which indicate the orientation of people to society, leadership, knowledge, group life, and the human condition. Common political usage refers to these groupings as conservative and liberal, respectively. The findings of this study lead the authors to speculate that the persistent and basic differences between these phenotypes--such as regarding religion, law, politics, medicine, morality, scientific inquiry, art, and education--'are related cultural expressions of a deep-seated genetic divide in human behavioral predispositions and capabilities.'"

The APSA site's home page also contains links to two recent articles concerning gay marriage.

From just the blurb, I'd have to say the research is suspicious. The words "absolutist" and "contextual" seem more likely to describe genetic predispositions to extermism and moderation. The researches seem to agree. From their abstract, "The results indicate that genetics plays an role in shaping political attitudes and ideologies but a more modest role in forming party identification."

Ok, on further reading, these guys are morons. To contextualize the absolutist/contextual split the researchers go far beyond the differences between political ideologies (conservative/liberal). They discuss religion (fundamentalists/secular humanists), law (procedural/substantive due process),art (traditional form-based realism/modern free-form impressionism),morality (enduring standards/situational ethics) and medicine (traditional AMA/wholistic). If they'd have left it there, I'd have said they're trying to shoehorn millenia of human endeavor into two convenient categories that define everything, ignoring things like there's more to religious thought than fundamentalism and human secularism or more to art than tradition and modernism, but no, they went farther citing the obvious split down genetic lines of sport between footbal and frisbee. It's hard to take anything they have to say seriously at that point. If they'd said something about competitiveness/recreationalism, maybe, but you're either genetically a football player or a frisbee flicker?