
Life on Earth can be traced back over three billion years into the past. Many examples of the Earth's former inhabitants are to be found in rocks, preserved as beautiful and fascinating fossils. The earliest life forms were bacteria and algae; these produced the oxygen that...

Life on Earth can be traced back over three thousand million years into the past. Many examples of the Earth's past inhabitants are to be found in rocks, preserved as beautiful and fascinating fossils. The earliest life forms were bacteria and algae; these produced the oxygen...