The Nature analysis of data from 117 mammal species and prior studies found that suppressing reproduction—through castration in males or sterilization/contraception in females—is associated with a 10–20% increase in life expectancy. Castration, but not vasectomy, extended male lifespan, suggesting sex hormones drive the effect. Female benefits largely reflect reduced costs of pregnancy and childcare, though ovary removal can increase frailty. The results point to an evolutionary trade-off between reproduction and longevity.
Study Finds Castration and Sterilization Often Increase Lifespan Across Mammals
Illustration by Tag Hartman-Simkins / Futurism. Source: Getty Images
A new analysis published in Nature suggests that suppressing reproduction—by surgical castration in males or by sterilization/contraception in females—is associated with longer lifespans across many mammal species, including humans.
What the Researchers Did
An international team examined data from 117 mammal species housed in zoos and aquariums and reviewed prior sterilization studies. They combined comparative data and historical records to assess how removing the ability or drive to reproduce affects adult survival.
Key Findings
The authors report that sterilization is associated with approximately a 10–20% increase in life expectancy on average, although the effect size varies by species, sex and timing of the procedure. For males, castration—which removes circulating sex hormones—was linked to lifespan extension, while vasectomy showed no similar benefit, implicating hormones rather than the mere prevention of reproduction. Effects were strongest when castration occurred before sexual maturity. For females, lifespan gains are likely driven by reduced energetic and physiological costs of pregnancy, lactation and parental care; however, removal of ovaries can sometimes leave women frailer or in poorer health.
“In females, lifespan increases after several different forms of sterilization, suggesting that benefits arise from reducing the substantial energetic and physiological costs of pregnancy, lactation and caring for offspring, rather than from a single hormonal mechanism,” said lead author Mike Garratt of the University of Otago. “In males, only castration extends lifespan — not vasectomy — which indicates that the effect comes from removing sex hormones.”
Historical and Experimental Evidence
Historical data support the pattern: a 2012 study showed Korean royal eunuchs from the 16th–19th centuries lived about 14–19 years longer than intact men. Laboratory studies in rodents also report improved late-life health after castration. The authors conclude that, across vertebrates, the hormonal drive to reproduce can constrain adult survival, reflecting an evolutionary trade-off between reproduction and longevity.
Context and Caution
These findings do not mean castration or sterilization is a recommended longevity treatment for humans. The effects vary by species and individual circumstances, and surgical sterilization has important physical and psychological consequences. The study highlights biological trade-offs that shape ageing but does not translate directly into a medical prescription for people.
Source: Garratt et al., Nature (analysis of comparative and historical data).
