32.1 The Skeletal System – We learned that bones are one of the most important tools used to study the evolution of vertebrates, including humans. Due to the structure and composition of bones, they are more likely than other tissues to be preserved after an animal dies. Bones are typically preserved by fossilization. This process replaces organic material in bones with minerals. Paleontologists compare fossilized bones to the bones of living animals to learn more about the anatomy of extinct animals and changes in species over time.