Relative Methods of Dating: Which Is Older, Younger, the Same?
Smith realized that certain rock layers contained certain types of fossils. Chemical analysis of bones and teeth can reconstruct diets and habitats based on plants the animals ate. Different environments are associated with different types of carbon dioxide (e.g., C3 or C4). Time, space, habitat, and diet are important factors in the interpretation of the fossil record. Fossils are the remains of organisms chemically changed into rock. Fossilization requires an anoxic environment, where decomposition is limited. (2) Potassium has a long half-life, and can be used to date fossils older than 200,000 years. Temperature drives climate, which is linked to biology and chemistry. Ancient temperatures are reconstructed through study of ocean dwelling organisms. One of the most dramatic changes in temperature occurred around 6 mya and was a cooling period in Earth’s history. Chemistry of Animal Remains and Ancient Soils: Windows onto Diets and Habitats i.The older the rock, the more primitive the fossil forms that were present.Georges Cuvier, the French naturalist, noted Smith’s results with great interest, and suggested that rocks containing similar fossils in France were the same age as those in England.