Interesting to think about. If some aspects of religious belief correlate with anatomic or biologic conditions that might be inherited, then societies that cull nonreligious peopke - or anyone who disagrees with the dominant religion - create a selective advantage to religiosity. Over the eons, its surprising there are any nonreligious left.
Although, possibly religious thought or critical thinking are the cause, or not the effect, of the fMRI differences.
Although, it could be BS. But Its interesting to speculate.