Unravelling gene -‐ environment interaction and fertility

There has been a massive delay in the age at first birth across Europe since 1970, which is now between 28-29 years (Mills et al. 2011). A primary reason for fertility postponement is the clash between the optimal biological period for women to have children with obtaining a higher education and building a career (Rindfuss et al. 1996; Brewster & Rindfuss 2000; Mills et al. 2011). The ability to control childbirth through contraceptives and cultural transformations surrounding the role of children has also played a central role (van de Kaa 1987). Explanations for changes in fertility behaviour in demography and sociology have almost exclusively relied on socio-environmental factors (Brewster & Rindfuss 2000; Kohler et al. 2002; Kravdal & Rindfuss 2008; Goldstein et al. 2009; Hobcraft, 2007).