We investigate the historical dynamics of the decline in fertility in Europe and its relation to measures of cultural and ancestral distance. We test the hypothesis that the decline of fertility was associated with the di§usion of social and behavioral changes from France, in contrast with the spread of the Industrial Revolution, where England played a leading role. We argue that the di§usion of the fertility decline and the spread of industrialization followed di§erent patterns because societies at di§erent relative distances from the respective innovators (the French and the English) faced di§erent barriers to imitation and adoption, and such barriers were lower for societies that were historically and culturally closer to the innovators. We provide a model of fertility choices in which the transition from higher to lower levels of fertility is the outcome of a process of social innovation and social ináuence, whereby late adopters observe and learn about the novel behaviors, norms and practices introduced by early adopters at the frontier. In the empirical analysis we study the determinants of marital fertility in a sample of European populations and regions from 1830 to 1970, and successfully test our theoretical predictions using measures of genetic distance between European populations and a novel data set of ancestral linguistic distances between European regions.