This is probably bullshit but it's interesting. The idea is morons with the god gene are more likely to believe in god fairies than normal people.

Wikipedia - God gene

The God gene hypothesis proposes that human spirituality is influenced by heredity and that a specific gene, called vesicular monoamine transporter 2 (VMAT2), predisposes humans towards spiritual or mystic experiences.[1] The idea has been proposed by geneticist Dean Hamer in the 2004 book called The God Gene: How Faith is Hardwired into our Genes.

The God gene hypothesis is based on a combination of behavioral genetic, neurobiological and psychological studies.[2] The major arguments of the hypothesis are: (1) spirituality can be quantified by psychometric measurements; (2) the underlying tendency to spirituality is partially heritable; (3) part of this heritability can be attributed to the gene VMAT2; (4) this gene acts by altering monoamine levels; and (5) spirituality provides an evolutionary advantage by providing individuals with an innate sense of optimism.