How the use of fire discovered?

How the use of fire discovered?
Man, obviously, did not invent fire. He only discovered how to use it, and harness its energy. This single discovery did more to raise early man above an animal existence than any other invention or discovery. Fire was the first force that gave man some independence from his environment. It became the basis for the vast amount of technology that followed in the years to come, and is still the basis for most of our modern technical processes.
Fire is a phenomenon that occurs in nature quite often. The eruption of volcanoes, the spontaneous combustion of decaying matter, and bolts of lightning all produce natural fires. Primitive man, living completely in the wilds, was in a good position to observe such production of fire. He also observed its effect – destruction.
Once early man had captured a bit of fire, perhaps a burning stick from a forest fire, he kept it going by adding small bits of wood from time to time.