23. Why does lifespan often vary across sexes?

Sex differences in lifespan reflect sex-specific evolutionary tradeoffs that shift the organism’s operation between performance, reproduction, and maintenance, thereby changing both the rate and composition of deleteriome accumulation and how strongly burden couples to failure. Because selection acts through fitness in a given niche, the two sexes often face different reproductive costs, competitive pressures, and risk exposures, so one sex may have higher damage, weaker late-life protection, different immune/inflammatory set points, etc. In this framework, the relevant question is not which sex has different aging mechanisms, but which sex-specific life-history constraints and maintenance architectures shape mortality.