Figure 1. “Tidens naturlære fig40” by Morten Bisgaard. From the book Tidens naturlære 1903 by Poul la Cour. By Morten Bisgaard [Public domain], via Wikimedia Commons, Licensed under Public Domain viaWikimedia Commons. https://commons.wikimedia.org/wiki/File:Tidens_naturl%C3%A6re_fig40.png
One's perspective makes a big difference in how one sees the function of the human body. An evolutionist looks at the human body as a collection of organs pieced together by random processes selected for survival by the challenges of the environment, while the creationist sees marvelous evidence for design and information that shout evidence of an omniscient creator.
Evolution theoretically occurs when mutations result in new traits. Advantageous traits increase an organism’s chance of survival and reproduction, thus preserving the trait. A trait that is neutral may or may not be preserved. Numerous traits are selected because their advantages for survival lead to the evolution of new organs and new species according to the theory. This is called natural selection.