Kin-Regulated Senescence: A Testable Model of Condition-Dependent Aging Evolution

Hypothesis

Aging isn't a programmed death mechanism but a condition‑dependent trait that can be attenuated when ecological cues signal high inclusive fitness returns from prolonged somatic maintenance. We're proposing a Kin‑Regulated Senescence (KRS) model in which individuals assess local relatedness and extrinsic mortality via chemosensory or social signals; high relatedness and low predation trigger downregulation of conserved pro‑aging pathways (e.g., IIS/mTOR) through epigenetic remodeling, thereby extending lifespan. Conversely, low relatedness or high extrinsic mortality maintain active senescence to free resources for kin.

Mechanistic Basis

• Signal integration: Nascent evidence shows that microbiome‑derived metabolites and pheromones can modulate histone acetylation at promoters of FOXO and SIRT genes 1; we hypothesize these signals carry kin‑specific information.
• Effector pathways: Reduced IIS/mTOR activity enhances autophagy and stress resistance, delaying accumulation of molecular damage 23.
• Feedback loop: Extended somatic maintenance increases offspring survival, reinforcing the signal that favors longevity—a positive feedback that can be selected under low extrinsic mortality.

Testable Predictions

1. In laboratory populations of Drosophila melanogaster manipulated to vary relatedness (e.g., clonal vs. outbred groups) while holding extrinsic mortality constant, high‑relatedness lines will evolve significantly slower aging rates after >50 generations, accompanied by decreased expression of IIS/mTOR targets and increased histone H3K27ac at longevity gene promoters.
2. Pharmacological blockade of putative kin‑signal receptors (e.g., odorant receptors ORco) will abolish the relatedness‑dependent lifespan extension, without affecting baseline mortality.
3. Conversely, introducing exogenous predation cues (e.g., alarm pheromones) into high‑relatedness, low‑mortality environments will accelerate aging phenotypes, restoring IIS/mTOR activity to levels seen in low‑relatedness controls.

Falsifiability

If evolution of aging is purely a non‑adaptive byproduct, manipulating relatedness or extrinsic mortality cues shouldn't produce consistent, heritable changes in aging rates or associated molecular signatures. Observing the predicted directional shifts would support the KRS model; absence of such effects would falsify the hypothesis.

Broader Implications

Should the KRS model hold, longevity interventions could be reframed as modulating the informational environment that signals kin value, rather than merely overriding metabolic pathways. This aligns with the disposable soma trade‑off but adds a layer of active, socially regulated control over senescence.