Genomic evidence for males of exceptional reproductive output (ERO) in apes and humans.

It is widely suspected that a small percentage of males have exceptional reproductive output (ERO) but progeny numbers of males are rarely measurable, even in humans. If we define the variance ratio of reproductive-output in males and females as α' = VM /VF , the ERO hypothesis would predict α' ≫ 1. Since autosomal, X, and, Y chromosomes are found in males 1/2, 1/3, and 100% of the time, their DNA diversities can inform about α'. For example, autosomal and Y-linked diversities are governed, respectively, by (VM  + VF )/2 and VM . When comparing the chromosomal diversities, α' appears to be near 20 for chimpanzees and orangutans, and 1-10 for gorillas. The exception is bonobos with α' < 1. In humans, extensive genomic data are coupled to a theory, developed herein, that can filter out selection influences on Y-linked diversities. Hence, the estimation of α' is rigorous, yielding values near or above 20, depending on the population. When α' > 10, the presence of ERO males is very likely. These analyses can be applied more generally to species with XY sex determination.