© 2015 Elsevier B.V. We used a natural experiment in Taiwan to test whether mating competition is a major motive for entrepreneurship. After being defeated in Mainland China, more than half million solders retreated to Taiwan in 1949. The soldiers were not allowed to get married until the military marriage ban was lifted in 1959. The policy change created a severe marriage squeeze for local men, triggering their animal spirits to engage in entrepreneurial activities. Empirical results show that local men exposed to high sex ratios as a result of the removal of the marriage ban were more likely to become entrepreneurs later on.