Reproduction’s Hidden Cost: How Fewer Offspring Extend Mammal Lifespans

Fewer offspring, longer life: A new study reveals how suppressing reproduction in mammals extends lifespan by 10% on average

A comprehensive analysis of 117 mammal species and 71 prior studies found that reproductive suppression increases lifespan by approximately 10% across the board.

The mechanisms differ by gender: testosterone removal in males and avoidance of pregnancy/nursing in females appear to drive these effects.

Female hamadryas baboons on hormonal contraception lived 29% longer, while castrated males saw a 19% increase in lifespan.

Johanna Stärk said:

"Zoos, where reproduction is carefully managed, provide a unique setting to study these dynamics."

Fernando Colchero added:

"This study shows that the energetic costs of reproduction have measurable and sometimes considerable consequences for survival across mammals."

Mike Garratt explained the biological pathway:

"This indicates that the effect stems from eliminating testosterone and its influence on core aging pathways, particularly during early-life development."

Historical data on Korean eunuchs from the Chosun Dynasty suggests they lived ~18% longer than non-castrated men, though these findings remain debated.

In contrast, human female sterilization (e.g., hysterectomy) is linked to a 1% lifespan reduction compared to non-sterilized women.

Researchers observed distinct mortality patterns: castrated males died less frequently from aggression/risky behavior, while females with suppressed reproduction had lower infection-related mortality. The study authors noted:

"Our findings show that the costs of reproduction are substantial and measurable across a vast range of mammals."

However, the research has limitations. Direct human evidence remains limited, and rodent studies suggest potential later-life health declines following early-life sterilization.

The evolutionary trade-off between reproduction and aging is clear, but extrapolation to human clinical applications requires caution.

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