This is the popular theory of evolution. And to emphasize that this is a theory, I put it in a silhouette of a man’s head. As the story goes, 4.5 billion years ago the earth is formed. 3.5 billion years ago there was organic soup. Life springs forth, first as plants 2 billion years ago. Then 600 million years ago there was a massive “explosion” of life – the Cambrian explosion. Sponges, worms, trilobites come on the scene, and through a process of mutation and Natural Selection evolve into animals. Finally, about 4 million years ago, man comes into being.