Two things we can learn from fossils.

fossils come from way back they can be left from dinosaurs and other species  

Explanation:

Using fossils, you can learn about extinct animals and plants, that's one. Two, you can learn about evolutionary traits and the fact that evolution exists.

Explanation:

the earth would become to overheated and everything alive on it will eventually die from overheating. plants will eventually die as well, water will evaporate, and it will be nothing but a hot planet without anything living on it.