# I want to be* *forever young

As the maximum age of a population decreases, it grows slower but converges faster, favouring programmed death in a changing environment.

## Aging is favored by natural selection in a changing environment

Draft for *Physical Review Letters* (2021)

Aging is thought to be a consequence of an accumulation of errors in the storage of genetic information. But mounting experimental evidence suggests that aging can be slowed or even stopped. To help resolve this mystery, we present a mathematical framework for understanding the evolutionary benefits of aging. We derive a mortality equation which governs the transition matrix of an evolving population. We find that its largest eigenvalue increases with the maximum age, but the spectral gap decreases. Remarkably, this is independent of the choice of fitness function. As the maximum age of a population decreases, the population grows slower but converges faster. Thus aging confers no benefit in a constant environment, but in a changing one can be favored by natural selection.

Draft for *Physical Review Letters* (2021)