Palaentological evidence

Ans. 1. Palaentology is the study of fossils. 

2. The process of fossilization takes a very long period of time. In order to study the fossil, the land is excavated. 

3. Fossils are collected from different levels of depths. A systematic study of these fossils and its occurance revealed that the deepest layers were found to have fossils of invertebrates. 

4. In layers above them were found prehistoric fish-like animals, amphibians, reptiles, birds and mammals respectively in that order. 

5. This suggests that perhaps this was the order in which the animals appeared on the earth.