Sex-specific mutation accumulation: A parsimonious explanation for sex differences in lifespan and ageing

This is a Preprint and has not been peer reviewed. This is version 3 of this Preprint. You must log in to post a comment. There are no comments or no comments have been made public for this article. This is a Preprint and has not been peer reviewed. This is version 3 of this Preprint. Add a Comment You must log in to post a comment. Comments There are no comments or no comments have been made public for this article. Sex differences in lifespan and ageing pervade the tree of life, yet their evolutionary origin is still debated. Adaptive trade-off models have long dominated the field but show mixed empirical support. Here we argue that mutation accumulation in genes with sex-biased fitness effects is the most parsimonious evolutionary cause of sex-biased ageing. Because anisogamy and ecology shape reproductive and survival schedules, natural selection weakens faster in one sex than in the other. The sex with the fastest declines in selection gradients with age will accumulate a greater load of late-acting deleterious mutations, leading to faster ageing and shorter lifespans. Critically, this mechanism works without requiring sex-specific resource allocation or genetic trade-offs. Therefore, it can resolve previously puzzling and contradictory variation observed in experimental and comparative studies because its predictions are context-dependent according to prevailing demographic patterns. Because this model requires only sex-biased gene expression and differences in late-age reproductive contributions towards future generations, it is sufficient to explain sexual dimorphism in lifespan and ageing across organisms with different sex determination systems. We discuss existing empirical support for this new model and outline approaches to test its predictions and quantify the role of mutation accumulation in the evolution of sex differences in lifespan and ageing. https://doi.org/10.32942/X2KM1G Life Sciences Senescence, life history evolution, Ageing, Sexual Dimoprhism, sex differences, Mutation Accumulation, Antagonistic Pleiotropy Published: 2025-11-17 23:50 Last Updated: 2026-01-05 23:52 CC-BY Attribution-NonCommercial 4.0 International Conflict of interest statement: None Data and Code Availability Statement: Not applicable Language: English