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The incidence of base substitutions in humans increases with the age of the father, which shows up as an increased incidence of mutational disorders in the children of older fathers. There is a less obvious implication: an extended period of high average paternal age in a population will lead to increased genetic load. We mention some societies that have had high average paternal age for many generations. This may explain some surprising regional differences in recent measurements of deleterious mutations. High average paternal age also influences life history evolution, strengthening selection against mortality in late life while weakening selection against child mortality.