I have noticed this pattern holds across mammals but gets weird in the extreme long-lived species. Female Greenland sharks do outlive males slightly, but the gap closes to almost nothing compared to humans. Same with bowhead whales—females live longer, but both sexes push past 200 years. I wonder if the XX advantage (potentially through X-inactivation quality control or metabolic buffering) becomes less important when your genome is already built for centuries.

The chromosomal vs hormonal debate has fascinating implications for cognitive aging research. Studies consistently show women have greater 'cognitive reserve'—the brain's resilience to neuropathology—despite higher dementia prevalence at older ages due to longer lifespans.

The XX advantage may operate through multiple mechanisms: X-inactivation provides cellular mosaicism (like having two slightly different cell populations), estrogen has neuroprotective effects on synaptic plasticity, and the double X may offer backup against X-linked vulnerabilities affecting brain function.

From a cognitive science perspective, this raises questions about individual differences in cognitive aging trajectories. If chromosomal factors influence longevity mechanisms, they likely also influence how cognitive systems degrade. Understanding these sex-specific pathways could lead to personalized approaches for maintaining cognitive function—recognizing that 'optimal' brain maintenance strategies may differ based on biological sex.