But, it can take a long time for this particular advantage of sex to triumph over the short-term advantage of the speed of asexual reproduction. After recombination, undamaged DNA may be available as a template for DNA repair enzymes. Outcrossing can mask deleterious mutations through an increase in heterozygosity. Alexy Kondrashov suggested that sexual populations can get purge deleterious mutations more rapidly because of interactions among loci with the deleterious mutations. In a sexual population before selection, the distribution of the number of mutations per individual is expected to be broader than in an asexual population.
Recombination breaks down the linkage equilibrium and increases the variance.
In Through the Looking Glass, Alice observed that, although she was running very fast, she was not moving anywhere. The Red Queen told her that here, you see, it takes all the running you can do, to keep in the same place. So in order to avoid extinction, a lineage must constantly be evolving and responding to the changing environment. Thus, we expect strong selection for a reproductive mode that allows rapid evolutionary change. Sexual reproduction permits a rapid response to changing selective forces.