Aging & Senescence · §8

The rate of aging: one biological age?

Across systems, aging is dominated by a single shared rate — 0.889 of the variance in the model — with smaller system-specific residuals. A biological-age axis exists and is dominant, but it is not the whole story: organs retain measurable independent rates. The shared-plus-residual structure is [V]; the absolute mapping is [O].

Decomposing per-system aging rates yields a dominant shared component of 0.889 plus residual per-system variation. This supports a single biological-age axis distinct from chronological age, while preserving organ-specific divergence — neither a pure global clock nor fully independent aging.

Shared rate versus per-system rates

Do all systems age at one rate, or each at its own? The decomposition gives a clear but two-sided answer: a dominant shared rate accounting for 0.889 of the variance, plus real system-specific residuals. A biological-age axis exists and dominates, yet organs are not locked to it.

This matches observation: biological age tracks chronological age strongly but imperfectly, and individual organs can age faster or slower than the body as a whole. The structure — one dominant axis plus residuals — is graded [V]; mapping it to an absolute clock is [O].