The more intelligent you are, the less likely you are to be religious, the less likely you are to be fundamentalist if you are religious, and the more likely you are to be an atheist.
And if you are an atheist, then you are statistically more likely to be more intelligent.
Within every society on earth, the group that are most intelligent always contain far more atheists per capita than a general cross-section sample of the entire society. We see this in its extreme when we examine the poll done of scientific Nobel Prize winners in the 1990s, which showed that 93% of such people were atheists, a statistic vastly different than any that would ever be found in a sample of people of average or below-average intelligence.
These facts are irrefutable.
It's important to note that atheism doesn't MAKE people more intelligent, but rather that atheism is one of many things that correlates with being more intelligent.