Energy Crisis

So far there were no oxygen molecules in the atmosphere. Some bacteria still live without oxygen today. We call them anaerobes ("an-air-obes"), meaning without oxygen. Lightening and other energy sources were making new molecules, and this was the food which the bacteria fermented.

As they spread they began to run out of food, so they had to find new sources of energy. Some began to eat minerals to get energy which they used to build their own food.