The Apolipoprotein-E (APOE) ε4 gene allele is the highest known genetic risk factor for developing Alzheimer’s disease (AD)1. Approximately 45% of carriers of the gene develop AD by the age of 85 years, compared to 10% of non-carriers1. It is not surprising therefore that much research has focused on seeking to identify early biomarkers related to the development of AD in ε4 carriers2,3,4,5,6,7,8,9,10,11,12,13. But why has this genetic allele, which has such obvious detrimental effects in old-age, been preserved in the human population world-wide?
One possible explanation is rooted in a concept that has emerged in evolutionary biology14. The antagonistic pleiotropy hypothesis proposes that some genetic alleles have different effects on the fitness of an organism at different ages. Therefore, a genetic allele, such as APOE ε4, which confers a disadvantage later in life, might…
