Here is one for the “simple, elegant science” folder: a new paper in PNAS by Julia Schroeder and colleagues that demonstrates a fitness disadvantage in offspring from older parents. While there a multitude of papers out there showing that gametes have reduced quality as an organism ages, this new work is the first to demonstrate this phenomenon in a natural system.
Schroeder et al show that a parent’s age has no effect on the longevity of their offspring, but the offspring of older parents have lower reproductive success over their lifetime. In addition, these effects are sex-specific: older males negatively affected their sons and older females negatively affected their daughters. To ensure that these effects weren’t primarily caused by environment, some of the offspring were moved to different parents before hatching out of their eggs.
Our results challenge the currently favored hypothesis in evolutionary biology and behavioral ecology that old age signals high quality in mating partners. Our results imply a substantial cost of reproducing with older, rather than younger, partners. The results inform increasing concern about delayed reproduction in medicine, sociology, and conservation biology.
Schroeder J., Nakagawa S., Rees M., Mannarelli M.E. & Burke T. (2015). Reduced fitness in progeny from old parents in a natural population, Proceedings of the National Academy of Sciences, 201422715. DOI: http://dx.doi.org/10.1073/pnas.1422715112