Evolution

The world was a test bed where nature could try out the mistakes caused by mutations. The new protein which had been made by accident was given a chance to prove itself. In most cases it was useless, or even harmful, and the life which carried it died.

But in a few cases it was useful, and it helped life. It may, for example, have made it grow slightly quicker than other life. After thousands of years other forms of life died out and were replaced by this new form. This process is called evolution by natural selection. By adding together lots of little changes life could slowly evolve into entirely new forms. Notice that evolution depended upon the death of less successful types of life. Death was the price that life paid for progress.

The life we see around us has evolved after many small accidental mutations in genes over billions of years.