The study compared the patterns of mortality and reproduction for 23 vertebrates, 10 invertebrates, 12 vascular plants and a green alga. Although it is predicted that evolution should lead to increasing mortality and decreasing fertility with age after maturity, the researchers found that there was immense diversity in both long- and short-lived species.
Of particular note is the rapid change in the timing of mortality for post-industrial humans — as illustrated in the paper by the example of Japanese women — suggesting that behavioural and environmental, rather than genetic, changes are the cause. In contrast to the upward trend in mortality with age found in humans and some other species, mortality in several species declines with age and, in some cases, — for example, the desert tortoise — this decline continues until terminal age (the point at which only 5% of individuals are still alive). Fertility patterns are similarly variable, with some species, such as the freshwater crocodile, exhibiting increased fertility until terminal age. The study demonstrates that modern humans exhibit extremely different patterns to many of the other species studied, leading the authors to caution that we should be careful not to assume that other species follow the same mortality and reproductive patterns as humans.
The work has been led by Owen Jones at the Max Planck’s Odense Centre, Denmark, and researchers from several different countries have contributed to the study. One of collaborators is Professor Johan Ehrlén from Department of Ecology, Environment and Plant Sciences, Stockholm University.
