A conversation is ticking along within the evolutionary sciences around whether or not religion is adaptive or exaptive. Richard Dawkins more recently weighed in with his updated thoughts;

Viewing a specific faith as an extended phenotype may be stretching it too far, but the human capacity for faith more generally may well be an expression of genes. That being said religions are memetic, not genetic. A son of Christian parents will not believe in the salvation of Christ if raised to be unaware of the dogma.