any theory of sex is incomplete until it addresses why there are 2 sexes (even if one organizm can carry both sexual organs it is still 2 distinct sexes). It may seems obvious, yet a science theory must address it scientifically. All the shuffling, flushing, etc.. of genes would also work in 3, 4, ... sexes schemas. It will have different statistical distributions and the theory must prove that whatever goal of sex existence, it is somehow optimal with 2.