Together, our empirical findings support the hypothesis that APOE ε4 was maintained by Darwinian adaptive value in environments with a high pathogen exposure, where reproduction has been favoured and where limited survival to later ages would have delayed detrimental effects of APOE ε4 that include atherosclerotic disease [1–4], Alzheimer’s disease [1,3,5,6], and accelerated cognitive decline. This evidence concerns the gene APOE and Mental deterioration.