They teach us what happened in Earth before we arrived. For example, if we had never found any dinosaur fossils, we would have no idea what happened. Fossils show us ancient life and what it was like back then.
Fossils help scientists learn about and discover ancient lifeforms that have died and fosilised. They also may help us date other fossils and rocks that are hidden deep in the earth. finding similar fossils of animals on different continents helped support the continetal drift theory, which became the theory of plate tectonics!
