The article does report that the conclusion is based on the assumption "if religion is an evolved domain", ie part of human instinct.
I'm not convinced it's that simple. I would need an explanation as to how religion can be assessed as an instinct in the same way as other instincts - suckling, for example. Perhaps the paper does this and it is not reported though.
Could there be any greater conceit, than for someone to believe that the universe has to be simple enough for them to be able to understand it ?