question: What do fossils do? answer: They provide evidence and give us clues to past life on Earth paragraph: Many plants and animal species have lived on Earth. Most are no longer alive. Only a tiny number of species still live on Earth. If not for fossils, we would know little about species that did not survive. Fossils provide evidence. They give us clues to past life on Earth. They tell us that life on Earth has changed over time. Fossils in younger rock Fossils can also tell us about how plants and animals lived in the past. Was it land or marine? Was the water shallow or deep? Fossils can even provide clues to ancient climates. They can tell us if it was warm or cold. Maybe it was cold or hot? Some places that are now cold were once warm. Some places that are now hot and dry were once wet and cool. Fossils provide a window into the past. 