In order to identify and learn more about Earth years before we came to be, PALEONTOLOGISTS study FOSSILS, EMBRYOLOGY, and DNA/MOLECULES to learn how organisms evolved. Fossils are the remains (essentially the structures) of a once lived organism, here you can compare species and identify whether they had a HOMOLOGOUS structure- meaning they share the same ancestor and structure, or have an ANALOGOUS structure- similar functions but different forms and ancestors. You can also identify a VESTIGIAL structure when looking at fossils, seeing if they have a certain component to them that they don’t use anymore being that it’s of no use anymore. This process as a whole is called COMPARATIVE ANATOMY, comparing physical structures of species. As for embryology, this study is most beneficial for when observing species that evolve the most, if not ONLY when they’re still developing in the embryo. You’re able to observe and identify species that either shared a recent common ancestor or evolved independently by looking at DNA/molecules. All species deal with the process of having some advantages, such as better survival skills and reproductive advantages, given to them by offsprings and sometimes spreading to the whole population, this process is called NATURAL SELECTION. With natural selection, organisms must also ADAPT to their habitat, which is where natural selection can be extremely helpful.