Somatotropic Axis’ Role in Ageing and Longevity Could Depend on Life-History Strategies of Species

It is often argued that food restriction and modulation of the somatotropic axis could increase lifespan in all species, and particularly in human beings. However, this rationale does not take into account the life-history strategies of species and the way they adapt to environmental challenges, particularly to food restriction. It is argued that, for short-lived species of a small size, the best strategy to survive starvation is staying at the same place and increasing lifespan, because they cannot migrate to discover new food sources, because of a high predatory load and/or an inability to cross long distances. Emigration is an appropriate strategy for long-lived species of a large size less at risk of predation. Because humans tend to emigrate when facing unfavourable conditions rather than staying at home, food restriction is not expected to increase lifespan in humans. As an outcome, modulating the somatotropic axis would probably not increase human lifespan, because increased lifespan has not been selected as a strategy: how a genetic pathway could modulate lifespan in the absence of any selective pressure?