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 <i>α'</i> = <i>V_M</i> /<i>V_F</i> , the ERO hypothesis would predict <i>α'</i> ≫ 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 <i>α'</i>. For example, autosomal and Y-linked diversities are governed, respectively, by (<i>V_M</i> + <i>V_F</i> )/2 and <i>V_M</i> . When comparing the chromosomal diversities, <i>α'</i> appears to be near 20 for chimpanzees and orangutans, and 1-10 for gorillas. The exception is bonobos with <i>α'</i> < 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 <i>α'</i> is rigorous, yielding values near or above 20, depending on the population. When <i>α'</i> > 10, the presence of ERO males is very likely. These analyses can be applied more generally to species with XY sex determination.