Selection on male longevity in a monogamous human population: Late-life survival brings no additional grandchildren

Abstract

Humans are exceptionally long-lived for mammals of their size. In men, lifespan is hypothesized to evolve from benefits of reproduction throughout adult life. We use multi-generational data from pre-industrial Finland, where remarriage was possible only after spousal death, to test selection pressures on male longevity in four monogamous populations. Men showed several behaviours consistent with attempting to accrue direct fitness throughout adult life and sired more children in their lifetimes if they lost their first wife and remarried. However, remarriage did not increase grandchild production because it compromised the success of motherless first-marriage offspring. Overall, grandchild production was not improved by living beyond 51years and was reduced by living beyond 65. Our results highlight the importance of using grandchild production to understand selection on human life-history traits. We conclude that selection for (or enforcement of) lifetime monogamy will select for earlier reproductive investment and against increased lifespan in men. © 2011 The Authors. Journal of Evolutionary Biology © 2011 European Society For Evolutionary Biology.