Change and Aging Senescence as an adaptation

TL;DR

This paper proposes an evolutionary model explaining aging as an adaptation to environmental change, where senescence helps lineages adapt faster by removing older, less suited individuals, despite individual costs.

Contribution

It introduces a novel model showing how senescence can be evolutionarily advantageous in changing environments, balancing individual costs with lineage-level benefits.

Findings

Senescence can lead to extinction of immortal competitors under changing conditions.

Older individuals are removed from the gene pool, facilitating faster adaptation.

Aging is an evolutionary response to environmental change, not just individual decline.

Abstract

Understanding why we age is a long-lived open problem in evolutionary biology. Aging is prejudicial to the individual and evolutionary forces should prevent it, but many species show signs of senescence as individuals age. Here, I will propose a model for aging based on assumptions that are compatible with evolutionary theory: i) competition is between individuals; ii) there is some degree of locality, so quite often competition will between parents and their progeny; iii) optimal conditions are not stationary, mutation helps each species to keep competitive. When conditions change, a senescent species can drive immortal competitors to extinction. This counter-intuitive result arises from the pruning caused by the death of elder individuals. When there is change and mutation, each generation is slightly better adapted to the new conditions, but some older individuals survive by random chance. Senescence can eliminate those from the genetic pool. Even though individual selection forces always win over group selection ones, it is not exactly the individual that is selected, but its lineage. While senescence damages the individuals and has an evolutionary cost, it has a benefit of its own. It allows each lineage to adapt faster to changing conditions. We age because the world changes.