Mutations are the only kind of variability generating mechanism in prokaryotes and asexually reproducing organisms. But in eukaryotes where sexual recombination occurs, even in one generation there is a marked reshuffling of genes in the chromosomes which amplifies the genetic variability in a population. The kind of variability generated by recombination is tested by natural selection in as many genetic backgrounds as possible and in as short time as possible (say in one generation). Thus one of the greatest and fundamental advantages of sexual reproduction is the generation of variability. Provided the populations are large, even if mutations do not exist, the mechanism of sexual recombination alone would be generating new genotypes for very long time.