A long-standing conjecture is that winner-take-all games such as patent races lead to the survival of risk-takers and the extinction of risk-averters. In many species a winner-take-all game determines the males' right to reproduce, and the same argument suggests that males will evolve to be risk-takers. Psychological and sociological evidence buttresses the argument that males are more risk-taking than females. Using an evolutionary model of preference-formation, we investigate to what extent evolution leads to risk-taking in winner-take-all environments. Journal of Economic Literature Classification Numbers: C7, D8.