Despite the talk of mutations, there is no genetics in this paper. No atheist genomes were sequenced and found to be mutated. Rather, Dutton et al. claim (mostly on the basis of a review of previous literature) that atheists have elevated rates of proxy measures of genetic health or ‘mutational load’, namely ill-health, autism, and left-handedness. This, they say, is consistent with atheism being a manifestation of “increasing genetic mutation affecting the mind”.
These arguments are unconvincing, to say the least. To take autism as an example, Dutton et al. cite a handful of small studies as suggesting that people with autism are more likely to be atheists. Even if this is true, it doesn’t mean that ‘mutational load’ is involved. It could just be that having autism makes you more likely to become an atheist – I don’t think this has ever been tested, but it seems plausible. Dutton et al. don’t consider this or any other non-genetic explanation for the correlation between atheism and autism.