Recapitulation theory

Recapitulation theory is an idea that used to be popular a long time ago. It said that as you grow up, you go through a cycle like the ones animals and plants have gone through during their long history on Earth. So a baby would start out like a fish, then become more like an amphibian (like a frog), then a reptile (like a lizard or turtle), then a mammal (like a dog or cat), and then a human. Because of this theory, some people thought that a baby growing inside its mom could be studied to learn more about how animals used to look a long time ago. Today, scientists know that this theory is not true.