Genetic differences help explain variation in political participation

According to an article in the American Political Science Review:

...individual genetic differences make up a large and significant portion of the variation in political participation, even after taking socialization and other environmental factors into account.

The authors give no explanation of how differences in our DNA are responsible for such an effect. 

But the answer is not difficult, when you realize that variations in motivation are genetic.  Not everyone wants to be President.  Most of us seek a "just master".  We would rather be followers, not leaders. You just can't teach motivation.

Our genes are responsible for identifying what makes us happy.  Some people are happy being altruistic.  Some are happy being ambitious.  The differences in "wants" and "desires" are accounted for by our genes.  As Schopenhauer wrote, you can do what you want, but you can't want what you want.

I assume people are attracted to the Democratic party (and left-leaning Public Radio) because they feel good about what it stands for.  Others (with a different set of genetic variants) are attracted to the Republican party (and Fox News).

I think the more interesting question is: how do our genes affect the construction of our mind and brain, to account for these differences in desires, pleasures, motivators?  How did our DNA create the brain in such a way that we can differentially get motivated by different qualities of political parties?