This paper documents a positive correlation between the genetic distance to the world technological frontier (United Kingdom, United States) and the year of the onset of the fertility transition across countries. This result is robust to controlling for a large set of geographical, climatic, historical, and institutional variables. Two main mechanisms could explain this reduced-form relationship. First, genetic distance to the world technological frontier can affect the onset of the fertility transition through its impact on the timing and intensity of technology adoption. Second, genetic distance to the technological frontier can capture other cultural differences and the process of diffusion of cultural norms that are related to fertility but not through technology adoption. We find suggestive evidence supporting both mechanisms.