Evolution and the Importance of Regeneration

It's thought that the kinds of cells that are necessary to have full regeneration, they would get plucked off by an active immune system. Salamanders and fish don't have great immune systems. The other answer is the cost of regeneration. It's really expensive to do. Almost every innovation that was necessary for the revolution of the invasion of land or the origin of flight as you open the conversation with happened well before the revolution itself.