18. Disposable Soma Captures Trade-Offs but Does Not Explain Aging’s Origin

Disposable soma is the concept that, because resources are finite, evolution favors allocating enough to somatic maintenance to ensure survival through development and reproduction, but not enough to keep the soma indefinitely (8). This captures an important trade-off, yet it does not explain why aging emerges or exists in the first place: imperfect biological systems inevitably generate deleterious changes, and even unlimited resources leave residual deleteriome accumulation, especially in organisms with long-lived, poorly replaceable cells (e.g., neurons) (2, 5). In the deleteriome framework, the central variable is not resources per se but net damage flux: how much burden is produced by normal function and exposures, and how effectively it is prevented, repaired, removed, diluted by turnover, or buffered by redundancy. Allocation is one way evolution and interventions reshape that flux (e.g., shifting growth and reproduction toward repair thereby changing life history), but the same energetic budget can yield very different lifespans if it is spent in ways that generate more or less damage (e.g., rodents versus birds), or if tissues differ in renewability and failure thresholds.