Razib's regression analysis on religion and abortion attitudes across countries is pretty illuminating in this regard.

1) It is clear that religion correlate with opposition to abortion in the vast majority of nations.

2) But, the attitudes of religious people and non-religious people track each other so that the irreligious in nation X may oppose abortion much more than the religious in nation Y.

The hypothesis here isn't that personal characteristics determine policy preferences directly, but that they predispose a person to be more receptive to (e.g.) left vs. right arguments within their society. Context is everything, though: leaning conservative in Sweden means endorsing policies that would be radically left in the USA.

Wrong (with all due respect). Genes (a subset of biological differences) affect politics a lot. To give just one source of evidence, my first hit googling "genes politics" is this New York Times coverage. Not only does "socioeconomic status, and presence of other meme complexes (religion, national identity etc) leave a great deal of variance unexplained, they are also affected by genes.

Once we're into correlations with socioeconomic status, etc., we need Judea-Pearl-style causal analysis to suss out how determinative biological differences are. (Genotypes are presumably occasionally causes and never effects, but that won't apply to phenotypes.)