Comment by schrodingersCat

Its generally understood that traits that encourage reproduction regardless of whether or not they encourage fitness will outperform other traits (https://en.wikipedia.org/wiki/Sexual_selection). This is why you will see the appearance of coloration and seemingly useless adaptations faster than actually beneficial traits within a population (i.e. a giraffe's neck; its not for reaching those high leaves). Natural selection is generally concerning traits that promote survivability over time, a much slower process. A major hypothesis is that sexual selection may be a driving force behind differentiation of the sexes, probably originating from genetic information sharing among single-celled organisms. A competing hypothesis is that there is an intrinsic advantage to sexual reproduction versus asexual reproduction. I generally favor the former hypothesis because it generally fits the "short-sightedness" principle of evolution.