What doesn't kill you makes you (and your descendants) stronger: a perspective on early-life exposure to human-induced challenges as a trigger of compensatory mechanisms

Although the negative impact of human-induced environmental effects on bird populations has been widely demonstrated, the question of whether adaptive strategies may potentially arise as a result of unforeseen challenges is still unclear. Despite their obvious pervasive effect, human-induced perturbations may activate, under certain circumstances, physiological and behavioural compensatory mechanisms that allow individuals to cope with stressful environments. In this Viewpoint, we highlight that understanding such compensatory responses (or the lack of them) requires adopting an ontogenetic and transgenerational perspective, as well as a multidisciplinary approach that integrates physiology, ageing biology and related molecular processes, and behaviour. During development, an organism's phenotype is subject to reorganization in response to environmental input. Thus, we focus on how early-life (human-induced) experiences potentially shape, even prenatally, specific physiological and molecular processes (i.e. protection against oxidative damage and telomere maintenance mechanisms), or lifelong reproductive strategies (i.e. maternal allocation into eggs), and how these, in turn, may activate physiological and behavioural adjustments across generations. To test whether adjustments in the developmental trajectory may allow individuals to make ‘the best of a bad situation' or even increase their performance (or that of their offspring) in anthropogenic environments, we call for studies that use a lifelong approach and explore transgenerational effects. We also propose experimental designs to help advancement in the field.