There is a long established idea that oxygen is the prerequisite element for the creation of life on earth. However, scientists have demonstrated there were some primordial life forms which could survive and flourish without any oxygen. They found some specimens of 2.52 billion-year-old sulfur-oxidising bacteria. They were exceptionally large, spherical-shaped, smooth-walled microscopic structures much larger than most modern bacteria. Besides, scientists have also discovered almost similar kinds of single-celled organisms that live in deepwater sulfur-rich ocean settings today, where even now there are almost no traces of oxygen and no sunlight can enter.