Complex sentence: Adaptationism is an approach to studying the evolution of form and function that attempts to frame the existence and persistence of traits on the scenario that each of them arose independently due to how that trait improved the reproductive success of the organism's ancestors.
Split into simpler sentences: Adaptationism is an approach to studying the evolution of form and function. It attempts to frame the existence and persistence of traits, assuming that each of them arose independently and improved the reproductive success of the organism's ancestors.