Is it possible to slow the rate of ageing, or do biological constraints limit its plasticity? We test the ‘invariant rate of ageing’ hypothesis, which posits that the rate of ageing is relatively fixed within species, with a collection of 39 human and nonhuman primate datasets across seven genera. We first recapitulate, in nonhuman primates, the highly regular relationship between life expectancy and lifespan equality seen in humans. We next demonstrate that variation in the rate of ageing within genera is orders of magnitude smaller than variation in pre-adult and age-independent mortality. Finally, we demonstrate that changes in the rate of ageing, but not other mortality parameters, produce striking, species-atypical changes in mortality patterns. Our results support the invariant rate of ageing hypothesis, implying biological constraints on how much the human rate of ageing can be slowed.

Significance: Extensive care of offspring by mothers is a fundamental trait of all mammals, including humans, and the loss of a mother can be catastrophic for offspring. Here, we identify previously undocumented ways in which the death of a mother affects her offspring, using long-term, longitudinal data from seven primate species. First, females that experience early maternal loss are often less able, as adults, to produce offspring that survive to maturity. Second, in some species young offspring are more likely to die if their mother is facing impending death (death in the next few years), even while she is still alive. This work has important implications for our understanding of the evolution of the long life spans that primates exhibit.