For a long time, aging was thought to be caused by the progressive accumulation of molecular damage, and therefore late interventions were considered largely ineffective. However, in the nematode C. elegans, reducing the activity of the insulin receptor DAF-2 from birth doubles lifespan, while attempts to do this in adulthood using RNA interference produced no effect. This reinforced the belief in the irreversibility of age-related changes. The new work stands apart from classical theories and sits alongside research on the evolution of aging and cellular mechanisms, but offers a different view: the key role is played not by accumulated damage but by the dynamic instability of physiological systems.
The team used genetically modified nematodes in which the DAF-2 receptor is tagged with a special label (a degron) that allows the protein to be rapidly destroyed upon addition of auxin. The system is reversible: after auxin is removed, the receptor is restored. This makes it possible to precisely switch the signaling pathway on and off at any age. The intervention was started on day 21 of adult life, when 75% of the population had already died. The researchers then built a mathematical model based on the stochastic Langevin equation, in which the state of the organism is described by a single variable, and death occurs upon first reaching a critical threshold. The model parameters were tuned to reproduce the experimental survival curves.
Late destruction of DAF-2 in 21-day-old nematodes extended their lives by an average of 26 days, whereas control individuals lived only 4 more days. Total lifespan doubled and reached the same maximum as with intervention from an early age. At the same time, many age-related pathologies, such as pharyngeal degeneration, gonadal atrophy, and uterine tumors, did not disappear. However, cuticle breakdown stopped, resistance to heat and osmotic stress was restored, and protein aggregates partially dissolved. The Langevin model reproduced these results: the intervention lowered the instability parameter without changing the noise level and without resetting the accumulated state.
The work shows that late life extension in short-lived organisms does not require rejuvenation or the removal of damage. It is enough to change the dynamic parameters of the system, making it less unstable. This distinguishes the approach from damage-accumulation models and from neighboring studies that focus on molecular mechanisms or evolutionary aspects. Here, for the first time, a quantitative physical model is proposed that explains why the intervention is equally effective in young and old age. For humans, this means that the search for anti-aging therapies should aim not at erasing damage but at stabilizing regulatory networks.
The model can be extended to other species, including humans, where dynamics remain stable for most of life and instability grows only in old age. In that case, interventions that change dynamics would produce only a temporary effect, and extending maximum lifespan would require slowing the accumulation of entropic damage. It also remains to be determined which physiological variables govern proximity to the death threshold, and whether they can be measured in longitudinal studies.
The results will influence gerontology, biophysics, and systems biology by offering a new language for describing aging as a dynamic process. They may also change the strategy for discovering anti-aging drugs, shifting the emphasis from eliminating damage to modulating stability.
It is necessary to identify the specific biological variables corresponding to the dynamic coordinate z in the model and to develop methods for measuring them in living organisms. The model's predictions also need to be tested in other species and in longitudinal human studies.
The work is directly connected to an unsolved problem in gerontology: why interventions that are effective in short-lived species often fail in long-lived ones. The proposed model offers an explanation through differences in dynamic stability and indicates that different targets must be sought for humans. The nature of the 'control variables' of aging and whether they can be measured also remain open questions.
The nematode C. elegans has a stable life form as well: the dauer larva, which can wait out unfavorable conditions for months with almost no aging. Intervention in the DAF-2 signaling pathway apparently partially activates this stability program even in adult worms.
The idea that aging can be 'switched off' by changing the parameters of a system rather than repairing it echoes Greg Egan's novel Permutation City, where people manage their biological state through software settings.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.