Sex Ratio and Natural Selection at the Human ABO Locus

Abstract

Natural selective effects of ABO maternofetal incompatibility depend on age, sex and gene frequency. This study focuses on differences of fitness according to age and sex. Calculations of genotype frequencies weighted by fitness lead to the hypothesis that forces of natural selection would favor an association of excess males with type O. Studies of polymorphic populations and homogeneous·populations provide empirical support for the hypothesis.