What do we know about the evolution of reptiles?

 Once there were no reptiles upon land. The earliest reptiles lived in the sea. More than 250 million years ago, they journeyed to the shore in search of food. Forests of ferns and other vegetation covered the land in that time. Plant eating insects appeared, and the early reptiles moved to the land in search of these insects. The competition for life in the sea may also have forced them to make the shore their home, and to seek food there. They developed legs for walking around, lungs for breathing air, and scales for protection. Gradually, they evolved into reptiles fully adapted for life on land.

 No one was actually present to watch the evolution of reptiles! Fossils, the remnants of prehistoric animals and plants helped the scientists in this respect. Scientists argue about the order in which separate adaptations such as the legs and the lungs appeared. However, they agree that the most important adaptation was the reptilian egg.