What doesn’t kill you makes you (and your descendants) stronger: 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 adjustments may potentially arise as a result of unforeseen challenges is still unclear. Despite their obvious pervasive effect, human-induced challenges may activate, under certain circumstances, physiological and behavioural compensatory mechanisms that allow organisms to cope better with an altered and distressful environment. 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, molecular processes and behaviour. Given the outstanding capacity for plasticity during development, 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), and lifelong reproductive strategies (i.e., maternal allocation into eggs), which may in turn activate physiological and behavioural adjustments across generations. To test whether such adjustments in the developmental trajectory allow individuals to make “the best of a bad situation” or even increase their performance or that of their offspring in human-altered environments, we call for studies using a lifelong approach and that explore transgenerational effects. We thus propose experimental designs that could help the advancement in the field.