Ageing purpose: another thrifty genotype.

For evolutionary biology, ageing is a non-adaptive process. The 'disposable soma' theory proposes that senescence is the consequence of a reduction in the energy invested in the processes of cell maintenance and repair due to the fact that it is more beneficial to invest it in reproduction. Recently, various genes have been identified whose mutations modify the life span of certain animals. Most of these genes are related to energy metabolism, especially insulin, IGF-1 and their receptors. Furthermore, it has also been demonstrated that there is a modification in metabolic pathways during ageing. As a result, the energy-storing pathways are strengthened and there is a reduction in the pathways that use energy. All these findings suggest that ageing is a strategy designed by natural selection to save energy, in accordance with other saving strategies. This way the energy that is not used can be dedicated to offspring to improve their pre-reproductive survival.