6. Lifespan Plasticity Reflects System-Level Tuning of Damage, Maintenance, and Buffering

Evolution can tune the system-level parameters that govern i) damage/burden production, ii) maintenance/renewal capacity, and iii) how burden is buffered and translated into failure. Species longevity is therefore an evolved systems property, a coadapted set of processes, such as repair, turnover, buffering, stem-cell function, tissue architecture, cancer/ immune control, which are scaled by selection to ecological niche and extrinsic mortality as well as body size, temperature, and life history. Modest shifts in these constraints (even between close relatives) can rapidly reweight what selection can afford, and thus reoptimize the whole maintenance package. High-leverage traits are those that reduce the effective hazard landscape and justify stronger long-term investment: lower extrinsic mortality (e.g., safer ecology), slower life history (delayed maturation, extended development), and architectures that better prevent local deleteriome from cascading into organismal failure (improved buffering/redundancy, tighter cancer control, better immune balance, more effective renewal in key tissues, etc.). This is also why correlates of longevity across species need not match within-species interventions (69): across species, evolution co-optimizes many traits at once, whereas interventions perturb an already optimized design and often expose tradeoffs (71).