Why would natural selection not occur without genetic variations in species

Natural selection cannot occur without genetic variation because without genetic variation all the species would be the same and as such there would be no fitter species thus nature cant select one for survival.

Natural selection only occurs when there is a superiority within a species set. If there is no genetic variation, no single animal is any better than the next, making the presence of superiority impossible and survival left up to chance. In this case it would be considered genetic continuity.