Hypothesis: Extrinsic Mortality Cues Activate a Conserved Extracellular Vesicle-Mediated Aging Program

Core idea: Aging is not a passive accumulation of damage but an actively regulated, population‑level program that is switched on by ecological cues predicting high extrinsic mortality. The program is carried out by a conserved network of extracellular vesicles (EVs) that transmit mito‑derived danger signals and pro‑inflammatory cargo across tissues, establishing a systemic state of inflammaging that accelerates senescence. When extrinsic mortality is low, the same EV network is restrained, allowing longevity mechanisms to dominate.

Testable predictions

1. Cue‑dependent EV release: In model organisms (e.g., Drosophila or killifish), experimentally increasing perceived extrinsic mortality—through predator cues, high population density, or controlled mortality of conspecifics—will raise the concentration of circulating EVs containing mitochondrial DNA and IL‑1β‑like cytokines within 24 h. Conversely, reducing these cues will lower EV levels.

2. EV‑mediated lifespan manipulation: Pharmacological inhibition of EV biogenesis (e.g., using GW4869 to block neutral sphingomyelinase) or genetic knockdown of EV‑loading proteins (e.g., Alix, TSG101) will blunt the mortality‑cue‑induced acceleration of aging markers (p16^INK4a^, SA‑β‑gal, proteomic carbonyls) and extend lifespan even under high‑cue conditions. In low‑cue environments, the same interventions will have minimal effect, indicating pathway specificity.

3. Cross‑species conservation: Comparative EV proteomics across species with contrasting lifespans (rockfish, naked mole‑rat, mouse) will reveal a conserved core set of senescence‑associated EV proteins that are upregulated in short‑lived, high‑mortality lineages and downregulated in long‑lived, low‑mortality species. This pattern should correlate with the 2,737 amino‑acid changes previously linked to longevity [4].

Mechanistic rationale

The hypothesis bridges non‑programmed and programmed views by proposing that natural selection has shaped a conditional aging program: genes that enhance early‑life fitness also equip organisms with a rapid‑response EV system that can be summoned when survival prospects decline. This system is costly to maintain (hence its retention only when needed) but provides a decisive advantage by clearing older individuals, reducing kin competition, and reallocating resources to younger, more reproductive cohorts. The EV cargo includes oxidized mitochondrial DNA, lipids, and IL‑1 family cytokines, which together trigger NF‑κB‑driven inflammaging—a pathway already implicated in age‑related pathology [1]. Because the EV machinery is genetically encoded and can be modulated, interventions that target EV release or cargo loading can negotiate with the evolved logic rather than simply overriding it, aligning with the seed idea that longevity medicine should work with the evolutionary program.

Falsifiability

If experiments show that extrinsic mortality cues do not alter circulating EV concentrations, or that EV inhibition fails to modify mortality‑cue‑driven aging across species, the hypothesis would be falsified. Likewise, a lack of conserved senescence‑associated EV signatures across long‑ and short‑lived taxa would undermine the claim of an evolutionarily tuned, population‑level aging program.