APOE and Alzheimer disease: Chimpanzee ApoE differs from human by 9 amino acids; both share arginine R112 and R158.1–5 Chimpanzee ApoE from samples of wild-caught and captive have not shown coding variants, unlike in humans.4 ApoE3 is globally the most prevalent, with cysteine substituted for arginine at residue 112 of chimpanzee and spread in H sapiens within the last 200,000 years.6 Aging humans are also unique among the anthropoids in developing advanced neurodegeneration of Alzheimer’s disease (AD) and related disorders for which ApoE4 is a major genetic risk factor.