Thomas F. auteur aut IRD Giraudeau M. auteur aut IRD Renaud F. auteur aut IRD Ujvari B. auteur aut IRD Roche Benjamin auteur aut IRD Pujol P. auteur aut IRD Raymond M. auteur aut IRD Lemaitre J. F. auteur aut IRD Alvergne A. auteur aut IRD text journalArticle eng text/pdf reformatted digital access Why a postfertile stage has evolved in females of some species has puzzled evolutionary biologists for over 50 years. We propose that existing adaptive explanations have underestimated in their formulation an important parameter operating both at the specific and the individual levels: the balance between cancer risks and cancer defenses. During their life, most multicellular organisms naturally accumulate oncogenic processes in their body. In parallel, reproduction, notably the pregnancy process in mammals, exacerbates the progression of existing tumors in females. When, for various ecological or evolutionary reasons, anticancer defenses are too weak, given cancer risk, older females could not pursue their reproduction without triggering fatal metastatic cancers, nor even maintain a normal reproductive physiology if the latter also promotes the growth of existing oncogenic processes, e.g., hormone-dependent malignancies. At least until stronger anticancer defenses are selected for in these species, females could achieve higher inclusive fitness by ceasing their reproduction and/or going through menopause (assuming that these traits are easier to select than anticancer defenses), thereby limiting the risk of premature death due to metastatic cancers. Because relatively few species experience such an evolutionary mismatch between anticancer defenses and cancer risks, the evolution of prolonged life after reproduction could also be a rare, potentially transient, anticancer adaptation in the animal kingdom. specialized 020 17 12 e3000565 [19 p.] 2019 1544-9173 https://www.documentation.ird.fr/hor/fdi:010077754 10.1371/journal.pbio.3000565 1544-9173 [F B010077754] https://www.documentation.ird.fr/hor/fdi:010077754 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers20-01/010077754.pdf IRD - Base Horizon / Pleins textes 2020-02-05 2025-02-24 fdi:010077754 fre