Evolution is the gradual increase in complexity of a system…
Evolution is the gradual increase in complexity of a system or life form. These changes are positive and negative with the positive changes giving the life form a competitive advantage and therefore become permanent. The changes are infinitesimal in scope and transforms the life form over enormous periods of time.
Now consider a single cell creature or multiple cell creature. The life form multiples by dividing and forming two creatures. This form of multiplication is both simple and straightforward. In cell biology, mitosis is a part of the cell cycle when replicated chromosomes are separated into two new nuclei. Cell division giving rise to genetically identical cells in which the chromosomes number is maintained.
So imagine how an organism could evolve so that reproduction occurred by sex. The organism would have to simultaneously obtain compatible male and female sex organs in one huge step. But it’s even better, each sex would have to carry exactly half of the DNA code of the original life form and have the cellular coding to recombine so an offspring could form. There is no evolutionary path for reproduction that produces sex.
So when it is all said and done sex kills evolution.