This paper presents a theory in which increases in female labor force participation and reductions in the gender-wage gap are generated as part of a single process of demographic transition, initially characterized by reductions in mortality and fertility. The paper suggests a relationship between gains in life expectancy and changes in the role of women in society that has not been identified before in the literature. Mortality reductions affect the incentives of individuals to invest in human capital and to have children, with implications for female labor force participation and the wage differential between men and women. The paper also presents some empirical evidence to support the predictions of the theory.