ArticleEvolution letters2022
How much does the unguarded X contribute to sex differences in life span?
Article in Evolution letters, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 17 papers.
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
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Who cites it
17 citing papers in PubMed, 26 citations in OpenAlex.
- Asymmetric life-history trade-offs shape sex-biased longevity patterns.Nature communications · 2026Article
- Transcriptome analysis of ageing in a long-lived seabird reveals sex-specific differences across age classes in immune and DNA repair pathways.Frontiers in aging · 2026Article
- Widespread sex-biased gene expression reflects female-biased longevity in a species with environmental sex determination.bioRxiv : the preprint server for biology · 2025Article
- Epigenetic Clock Analysis of Sex Chromosome Aneuploidies.Aging cell · 2025Article
- Sexual selection drives sex difference in adult life expectancy across mammals and birds.Science advances · 2025Article
- Sex differences in DNA methylation in bats.Annals of the New York Academy of Sciences · 2025Article
- An Extension of Muller's Sheltering Hypothesis for the Evolution of Sex Chromosome Gene Content.Molecular biology and evolution · 2025Article
- Transposable element expression is associated with sex chromosome number in humans.PLoS genetics · 2025Article
- X*Y females exhibit steeper reproductive senescence in the African pygmy mouse.Proceedings of the National Academy of Sciences of the United States of America · 2025Article
- Sex as a biological variable in ageing: insights and perspectives on the molecular and cellular hallmarks.Open biology · 2024Review
- The influence of sex-specific factors on biological transformations and health outcomes in aging processes.Biogerontology · 2024Review
- Moderate evidence for the sex-dependent effect of poisoning on adult survival in a long-lived raptor species.Ecology and evolution · 2024Article
- Polygenic response of sex chromosomes to sexual antagonism.Evolution; international journal of organic evolution · 2024Article
- The evolution of aging and lifespan.Trends in genetics : TIG · 2023Review
- Sex-biased gene expression in nutrient-sensing pathways.Proceedings. Biological sciences · 2023Article
- Genetic sex determination, sex chromosome size and sex-specific lifespans across tetrapods.Journal of evolutionary biology · 2023Article
- Fourth Report on Chicken Genes and Chromosomes 2022.Cytogenetic and genome research · 2022Review
Corrections and comments
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Authors and funding
4 authors at 2 institutions in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Females and males often have markedly different mortality rates and life spans, but it is unclear why these forms of sexual dimorphism evolve. The unguarded X hypothesis contends that dimorphic life spans arise from sex differences in X or Z chromosome copy number (i.e., one copy in the "heterogametic" sex; two copies in the "homogametic" sex), which leads to a disproportionate expression of deleterious mutations by the heterogametic sex (e.g., mammalian males; avian females). Although data on adult sex ratios and sex-specific longevity are consistent with predictions of the unguarded X hypothesis, direct experimental evidence remains scant, and alternative explanations are difficult to rule out. Using a simple population genetic model, we show that the unguarded X effect on sex differential mortality is a function of several reasonably well-studied evolutionary parameters, including the proportion of the genome that is sex linked, the genomic deleterious mutation rate, the mean dominance of deleterious mutations, the relative rates of mutation and strengths of selection in each sex, and the average effect of mutations on survival and longevity relative to their effects on fitness. We review published estimates of these parameters, parameterize our model with them, and show that unguarded X effects are too small to explain observed sex differences in life span across species. For example, sex differences in mean life span are known to often exceed 20% (e.g., in mammals), whereas our parameterized models predict unguarded X effects of a few percent (e.g., 1-3% in
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