Sexual reproduction in Nature requires two sexes, which raises the question
why the reproductive scheme did not evolve to have three or more sexes. Here we
construct a constrained optimization model based on the communication theory to
analyze trade-offs among reproductive schemes with arbitrary number of sexes.
More sexes on one hand lead to higher reproductive diversity, but on the other
hand incur greater cost in time and energy for reproductive success. Our model
shows that the two-sexes reproduction scheme maximizes the recombination
entropy-to-cost ratio, and hence is the optimal solution to the problem.Comment: 10 pages 5 figures. to appear in Bulletin of Mathematical Biolog