Abstract: Understanding the nature of birth rate decline in the postindustrial world is a crucial task for a broad range of experts. It remains unclear what became the major motive for the switch of reproductive models in the highly urbanized world: the growing role of economic expenditure in a competitive urban environment or the result of manifestation of the new cultural norms of reproductive behavior via diffusion changing the modern demographic landscape. The theoretical part of the work familiarizes the audience with the main conclusions of the two competing hypotheses: the impact of economic versus of cultural factors upon the current birth rate. The practical part represents a quantitative study. As a result of application of the statistical methods of analysis in interviewing the Russian citizens, the author assesses the impact of economic and cultural factors upon birth rate, considering the factor of increasing urbanization. The article applies an interdisciplinary approach, as well as introduces into the scientific discourse the new materials of evolutionary ecology as one of the bases of human reproductive behavior. The analytical part focuses on the questions of population density (urbanization), its influence on birth rate in the observed cultures, taking into account the economic parameters.