Some of the differences in our beliefs seem to be heritable.   "The Heritability of Attitutes: A Study of Twins," in Journal of Personality and Social Psychology in 2001, asked 339 twin pairs for their attitudes on 30 topics.  These attitudes had seven common factors, four of which moderate categories of beliefs:   

• Life: voluntary euthanasia, abortion on demand, birth control, and organized religion.
• Intellect: books, chess, education, and capitalism
• Equality: open-door immigration, distinct gender roles, racial discrimination, and getting along with others
• Punishment: death penalty for murder,  and castration for sex crimes

Genetic differences explained most of differences in attitudes to life and equality (66% and 55% of the variance respectively), but none (0%) of the attitudes to intellect and punishment. 

Read the whole thing at the "via" link above. I've repeated this many times, and I'm saying it again: Overcoming Bias is, in my opinion, the best blog on the Internet.