From nature to nurture – How genes and environment interact to shape behaviour

The question of nature vs nurture caused animated discussions during the first half of the 20 th century but is since long resolved: all animal behaviour is a result of both genetic and environmental factors. In the last couple of decades, biology has got access to new and unprecedented tools for analysing the genetic underpinnings of behaviour variation. In this paper, examples are given on how analyses have moved from gross estimates of heritability to detailed genetic mapping, with new insights into the genetic mechanisms causing differences in behaviour. At the same time, studies of the effects of environment and experience largely have been running in isolation from the genetic analysis. However, we are now in a position where we can start to understand the details of how genetics and environment interact, primarily through epigenetic mechanisms. Examples are given of how different experiences cause epigenetic modifications, that in turn regulate the expression of the genome. Furthermore, epigenetic modifications can be inherited and even possibly affect mutations specifically related to the experience causing the epigenetic change, opening the possibility for environmentally driven evolution. Lastly, examples are given of future research fields that may further advance our understanding of how nature and nurture interact, specifically how play behaviour and the gut-brain axis may affect (and be affected by) the epigenome. The paper concludes that unravelling the complex interaction between genome, environment and epigenome will give rise to a considerably more comprehensive picture of the nature-nurture interactions in shaping behaviour. • Nature and nurture are intimately connected • Genetic tools allow detailed molecular mapping of behaviour variation • Epigenetics is the mechanistic link between nature and nurture • Social play and the gut microbiome are two environmental factors that can affect the epigenome