Fire 700-400 kya

About 700 thousand years ago (although the date is uncertain and some say it was nearer 400 kya), Homo erectus probably learnt how to use fire. They could not make it, but they could probably keep it burning when they found it. It let them cook their food, keep warm, see in the dark and defend themselves against animals. This was a great step forward. People were probably the first animals to overcome their fear of fire. No doubt it was treated as a magical force, perhaps worshipped as a spirit.

So what is fire? It is the rapid oxidation of a fuel, usually a carbon-based molecule. As the atoms rearrange themselves, they release the energy previously stored in covalent bonds, as radiation in the form of heat and light. In the process, oxygen is consumed and carbon dioxide and water are released. In the diagram we use formaldehyde as an example of a carbohydrate burning.

Carbohydrate burns with oxygen to produce water and carbon dioxide