Here are some clips from a piece by Constance Holden reporting on presentations at the recent annual Behavior Genetics Association meeting.
Numerous studies over the past 2 decades...have indicated that genes have a significant influence over whether you're "liberal" or "conservative" on various political and social issues. Some heritability estimates have been as high as 50%. That's roughly the heritability found for many personality traits such as "extraversion" or "agreeableness," and it implies that, in a given population, about half of the variation in a particular trait is attributable to genetic differences.We are talking here about the fact that genetics are important, not really going after a complex behavior like political leanings at the molecular level. What is important is that:
Now James Fowler, UCSD, and grad student Christopher Dawes say they've produced fresh evidence that DNA also has a hand in the intensity of someone's partisan attachment and even in whether someone bothers to vote...they did that by crunching data from twin registries and the government's long-running National Longitudinal Study of Adolescent Health (NLSAH)...they matched data on voting by 396 Los Angeles-area twins, including identical (who share 100% of their genes) and fraternal (who average 50% genetic overlap) twins, obtained from Los Angeles voter-turnout records. All twins were same-sex pairs to avoid confounding results with sex differences. The researchers corrected for environmental factors such as whether more of the identical than fraternal twins were living together, which might inflate their degree of similarity. They concluded that the correlation for voting was much higher between pairs of identical (.71) than fraternal (.50) twins. From this they estimated the heritability of voting behavior--that is, whether people eligible to vote actually do so--at 53%, suggesting that at least half the individual variation can be traced to genetic influences. They found an even higher heritability--72%--when they replicated the study with data on 806 twins from NLSAH, they reported in the May issue of the American Political Science Review.
Several groups are now trying to correlate personality data with DNA markers from studies such as NLSAH, which contains DNA as well as behavioral data from many subjects, in hope of identifying specific genes that feed into underlying traits, such as "desire for cooperation," that Fowler, for one, believes have been selected for throughout human evolution. Studies so far have focused on the same genes that are of interest in psychiatric genetics--in particular those involved with neurotransmitters such as dopamine and serotonin that are known to be important in regulating higher brain activities.
social scientists are plunging into biological and evolutionary issues. At least some are starting to acknowledge that humans are genetically unique individuals and not just cloned pawns of their environment. And that suggests that prophets and pundits, however prescient, are probably never going to get much better at predictions than they are now.