The variety of species of mice around the world demonstrates the creatures' remarkable ability to adapt to different climates, altitudes and food sources.
Does Natural selection or evolution involve with this? it sounds like spiders and other Insects or bugs that have evolved to be able to have limbs in order to survive in a environments that would require extra limbs. probably from genes being passed on and also being mutated positively in order for the newer species to better adapt. the pair of legs could have been increased because of the environment that requires it and also as the mating changes it's basically survival of the fittest.