The Influence of Societal Changes on the Contribution of Genetics to Fertility Behavior

The heritability of fertility behavior altered during the profound societal changes that occurred from the 1950s onward in Norway. Societal changes modify the heritability of age at first birth and number of children, and the change in heritability varies by gender and outcome. A theoretical explanation that suggests norms weakened and opportunities broadened across the latter part of the twentieth century and into the early twenty-first century, thereby increasing heritability, falls short. Results provide some support for the hypothesis that the importance of genes increases during periods of societal change, when linked to the transition to dualearner families and family policy implementation. The study highlights the importance of considering societal structures and gender differences when investigating genetic influences on fertility behavior.