Can postfertile life stages evolve as an anticancer mechanism?

Area of Science:

• Evolutionary Biology
• Cancer Biology
• Reproductive Biology

Background:

• The evolutionary persistence of a postfertile stage in females across species remains a long-standing question in biology.
• Existing theories have not fully accounted for the interplay between cancer risks and the body's defenses against cancer.

Purpose of the Study:

• To propose a novel hypothesis integrating cancer risk and defense mechanisms into the evolutionary explanation for postfertile stages in females.
• To explore how the balance between oncogenic processes and anticancer defenses influences reproductive cessation and menopause.

Main Methods:

• This study employs a theoretical and conceptual approach, analyzing existing evolutionary and biological data.
• It examines the physiological impacts of reproduction, particularly pregnancy, on tumor progression in females.
• The framework considers species-specific and individual-level parameters related to cancer risk and defense efficacy.

Main Results:

• Reproduction, especially mammalian pregnancy, can accelerate the growth of existing tumors.
• When anticancer defenses are weak relative to cancer risk, continued reproduction can lead to fatal metastatic cancers.
• Ceasing reproduction or undergoing menopause may be an adaptive strategy to limit cancer-induced mortality and enhance inclusive fitness.

Conclusions:

• The balance between cancer risk and anticancer defenses is a critical, previously underestimated factor in the evolution of postfertile stages.
• Menopause and reproductive cessation may represent a transient anticancer adaptation in species facing an evolutionary mismatch between cancer risk and defense.
• This hypothesis offers a new perspective on the evolution of longevity and postreproductive life in females.