Why can't I believe? (is it a genetic predisposition?)

[tame_deuces]

My country has gone from being largely theist to being around 50/50 atheist/theist, and the majority of those theists aren't really theists beyond believing enough to click/answer yes on a survey (no praying, temple attendance etc).

This development has taken only around 150-100 years, and it seems like this would be much to fast for a 'believer's gene' to die out.