Complete raw dataset from The sex with the reduced sex chromosome dies earlier: a comparison across the tree of life

Many taxa show substantial differences in lifespan between the sexes. However, these differences are not always in the same direction. In mammals, females tend to live longer than males, while in birds, males tend to live longer than females. One possible explanation for these differences in lifespan is the unguarded X hypothesis, which suggests that the reduced or absent chromosome in the heterogametic sex (e.g. the Y chromosome in mammals and the W chromosome in birds) exposes recessive deleterious mutations on the other sex chromosome. While the unguarded X hypothesis is intuitively appealing, it had never been subject to a broad test. We compiled male and female longevity data for 229 species spanning 99 families, 38 orders and eight classes across the tree of life. Consistent with the unguarded X hypothesis, a meta-analysis showed that the homogametic sex, on average, lives 17.6% longer than the heterogametic sex. Surprisingly, we found substantial differences in lifespan dimorphism between female heterogametic species (in which the homogametic sex lives 7.1% longer) and male heterogametic species (in which the homogametic sex lives 20.9% longer). Our findings demonstrate the importance of considering chromosome morphology in addition to sexual selection and environment as potential drivers of sexual dimorphism, and advance our fundamental understanding of the mechanisms that shape an organism's lifespan.

诸多分类群的两性寿命存在显著差异，但这类差异的方向并非固定统一。以哺乳动物为例，雌性平均寿命往往长于雄性；而在鸟类中，雄性平均寿命则长于雌性。针对这类寿命差异，有一个广受关注的假说——无防护X假说（unguarded X hypothesis），该假说指出：异配性别（heterogametic sex）所携带的简化或缺如染色体（例如哺乳动物的Y染色体与鸟类的W染色体），会使其另一条性染色体上的隐性有害突变暴露无遗。尽管无防护X假说在直觉上颇具说服力，但此前从未有过大规模的系统性验证。本研究收集了横跨生命树8个纲、38个目、99个科的229个物种种群的雌雄寿命数据。元分析（meta-analysis）结果与无防护X假说一致：平均而言，同配性别（homogametic sex）的寿命比异配性别长17.6%。令人意外的是，本研究发现雌性异配物种（其同配性别寿命仅长7.1%）与雄性异配物种（其同配性别寿命长20.9%）之间的寿命性二态性（sexual dimorphism）存在显著差异。本研究结果证实，除性选择与环境因素外，染色体形态也应作为性二态性的潜在驱动因素纳入考量，这一发现深化了我们对塑造生物体寿命的核心机制的基础性认知。