Deformations/genetic anomalies are what lead to evolution. Every physiological change that has happened in a species began with one that was born deformed. Most deformations are detrimental and cause the animal to live a much shorter life, but in rare cases the deformation allows that animal to survive more efficiently than those with the original body form, and that particular animal lives longer and reproduces more than an average one. Then those offspring live longer and do the same, and eventually it’s virtually impossible to find a member of the species without the deformation, and they’ve reached the next stage of their evolution. Then eventually a new deformation arises that’s even better than the last one