A large-scale analysis of 117 mammal species found that preventing reproduction is associated with longer lifespans, suggesting a strong link between reproductive activity and life expectancy.
Why do some animals live for decades while others survive only a few years? Female elephants can reach 80 years of age, yet they typically produce only a small number of calves. Mice, in contrast, usually live just a few years, but in theory can have well over a hundred offspring. Evolutionary theory links these patterns to a core trade-off: species must divide limited energy between reproduction and maintaining the body.
A new large-scale study adds broad evidence that this balance influences longevity across many mammals, including humans.
An international research team that included scientists from the Max Planck Institute for Evolutionary Anthropology in Leipzig investigated how different ways of suppressing reproduction relate to lifespan in mammals.
They analyzed records from 117 mammal species kept in zoos and aquariums around the world and paired those data with a meta-analysis of 71 published studies. Across the datasets, animals receiving ongoing hormonal contraception or undergoing permanent surgical sterilization lived about ten percent longer on average.
The reproduction – survival trade-off
One reason may be that reproduction requires major biological investment. Pregnancy and lactation demand energy, and so do sperm production, mating behaviours, and parental care. Even outside of breeding, sex hormones such as testosterone and estrogen continue to affect growth, behavior, and aging, potentially drawing resources away from long-term body maintenance.
“Zoos, where reproduction is carefully managed, provide a unique setting to study these dynamics,” says Johanna Stärk, one of the authors. “Animals may receive contraception or sterilization to prevent breeding, creating natural comparison groups within the same environment.”
The longevity boost appeared across a wide range of mammals, including primates, marsupials, and rodents. In some cases the differences were especially large. Female hamadryas baboons given hormonal contraception lived 29 percent longer, and castrated males lived 19 percent longer.
“This study shows that the energetic costs of reproduction have measurable and sometimes considerable consequences for survival across mammals,” says Fernando Colchero, one of the study’s senior authors. “Reducing reproductive investment may allow more energy to be directed toward longevity.”
Both sexes live longer – but for different reasons
Although both sexes lived longer when reproduction was blocked, the underlying causes differed. Lead author Mike Garratt of the University of Otago explains that only castration—not vasectomy—extends male lifespan. “This indicates that the effect stems from eliminating testosterone and its influence on core aging pathways, particularly during early-life development. The largest benefits occur when castration happens early in life,” he says.
In females, multiple forms of sterilization increased lifespan, suggesting that the advantage comes from relieving the substantial physiological costs of pregnancy, lactation, and reproductive cycling. Ovary removal, which eliminates ovarian hormone production, still extends lifespan, although a meta-analysis of 47 laboratory rodent studies indicates potential trade-offs: later-life health may be impaired.
These findings may help explain the “survival–health paradox” seen in post-menopausal women, who typically outlive men but experience higher frailty and chronic disease burden.
Patterns of mortality also differed by sex. Castrated males were less likely to die from behavioral causes linked to aggression or risk-taking. Females with blocked reproduction were less likely to die from infection, consistent with the idea that the high energy costs of reproduction may lower the mothers’ immune-defense systems.
Insights from humans
Data on the effects of castration and sterilization in humans is rare. Some historical data, such as those of Korean Eunuchs in the pre-19th-century Chosun Dynasty, suggest that castrated men lived, on average, 18 percent longer than non-castrated men. However, these historical records need to be interpreted carefully, as their accuracy is debated. Among women, surgical sterilization for benign reasons (such as hysterectomy or oophorectomy) is associated with a small decrease in lifespan, only about 1 percent relative to comparable non-sterilized women.
“Reproduction is inherently costly,” the authors note. “However, human environments—through healthcare, nutrition, and social support—can buffer or reshape these costs.”
The study makes it clear that reproduction in mammals involves considerable biological costs—a fundamental evolutionary trade-off between reproduction and survival. These costs arise from an interplay of hormonally controlled processes and the manifold risks and stresses associated with reproduction. However, the exact mechanisms involved remain unclear and require further research. “Our findings show that the costs of reproduction are substantial and measurable across a vast range of mammals,” the authors conclude. “Understanding these trade-offs deepens our insight into how aging evolves and how males and females balance survival and reproduction differently.
NOTE – This article was originally published in Science Daily and can be viewed here
