We can simply explain this as the result of particular organisms as it thrives in a particular environment. Let us say we have a test animal X. This particular species evolved and have developed inherited traits in the expanse of time which contain a particular genetic makeup. These characteristics showed and evolved because of the adaptation of animal X in the nature to where it resides for a very long time. Nature plays a role to what would be the traits that could be present is a certain individual. As the traits are being passed down to the next generation through genetic crosses, the genes can be mutated through several factors that can eventually affect the characteristics of the offspring. Science plays a role in determining the effects in the mutation of the organism with respect to the nature where it belongs.