Fewer offspring, longer life: The hidden rule of mammal aging

Fewer offspring, longer life: The hidden rule of mammal aging Across mammals, fewer babies often mean more years of life-a striking evolutionary trade-off between reproduction and survival. Date: January 16, 2026 Source: Max Planck Institute for Evolutionary Anthropology Summary: A large international study reveals that mammals tend to live longer when reproduction is suppressed. On average, lifespan increases by about 10 percent, though the reasons differ for males and females. Castrated males avoid the harmful effects of testosterone, while females gain longevity by sidestepping the intense physical demands of pregnancy and nursing. The results underscore a powerful biological trade-off between making offspring and staying alive longer. Share: To the Point Longer lives across species: Limiting reproduction is linked to longer lifespans in many mammals, boosting life expectancy by about ten percent on average and sometimes even more. Different biology for males and females: Males live longer only when castration removes testosterone, while females gain longevity from any form of reproductive suppression, likely because avoiding pregnancy and lactation reduces heavy energy demands on the body. Shifts in how animals die: Castrated males are less likely to die from aggression or risky behavior, while females with blocked reproduction experience fewer deaths from infections, suggesting stronger immune defenses. Why Lifespans Differ Across Species Animals across the natural world age at dramatically different rates. A female elephant can live as long as 80 years, yet she produces only a small number of calves over her lifetime. By contrast, a mouse may survive just a few years but is capable of producing dozens of offspring. Evolutionary biology explains this contrast through a basic principle: energy is limited, and species must divide it between reproduction and maintaining their bodies. A new large-scale study offers fresh evidence that this trade-off plays a major role in shaping how long mammals live, including humans. An international team of researchers, including scientists from the Max Planck Institute for Evolutionary Anthropology in Leipzig, investigated how limiting reproduction influences lifespan in mammals. The study analyzed records from 117 mammal species living in zoos and aquariums worldwide and combined them with a meta-analysis of 71 previously published studies. Together, the data showed that long-term hormonal contraception and permanent surgical sterilization are linked to an average lifespan increase of about ten percent. The reproduction -- survival trade-off Producing offspring requires enormous biological investment. Pregnancy, nursing, sperm production, courtship behavior, and parental care all consume large amounts of energy. Even outside of active breeding, sex hormones such as testosterone and estrogen continue to affect growth, behavior, and aging, 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 lifespan benefits of reduced reproduction appeared across a wide range of mammals, including primates, marsupials, and rodents. In some cases, the effects were striking. Female hamadryas baboons given hormonal contraception lived...

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