Cross-Species Mortality and Fertility Patterns

Maximum longevity varies hugely across species, ranging from days to millennia. Reproductive output also varies by orders of magnitude. These patterns are part of the diversity of life history and result from the age-trajectories of mortality and fertility, which show comparable diversity. The familiar demographic trajectories of humans—increasing mortality and a hump-shaped fertility—are just one way to organize demography. Other mammals and birds show human-like patterns, but other species have increasing fertility and declining mortality rates with age. Others show no signs of aging at all. The author explores the correlates of these patterns and highlights the need to consider senescence from a broad taxonomic scope to truly understand the evolution of aging and life history patterns more generally.