Explore the evolutionary significance of sexual reproduction and genetic recombination in this thought-provoking lecture from the Santa Fe Institute's Annual Science Board Symposium. Delve into the enigma of sex, examining its costs and benefits through the lens of epistasis, modifier models, and the reduction principle. Investigate the impact of finite populations on sexual evolution, considering analytical models, simulations, and real-world examples like evening primrose. Gain insights into the Hill-Robertson interference and Miller-Fisher explanation while pondering the unanswered questions in the field. Conclude with a discussion on epigenetics and sex differences, broadening your understanding of this fundamental biological process.