Answer:
Artificial fire is primitive humans do not know how many years of exploration, in the long-term labor practice, constantly summarize the experience of fire and preservation of fire gradually invented.
Originally, human ancestors in the "repair" cave, or in the process of making stone tools, see the impact of rocks have Mars splash, and found that with iron ore or hematite as a hammer, quartz stone or flint can produce large sparks, these sparks, sparks sometimes fall on the dry branches and leaves, grass will burn.
Primitive people in order to make a tool, with a stone cone on the stick to spin drill, drill for a long time, will smoke and create fire. The ancestors were inspired by these repeated labor practices, understood the causal relationship, and invented the method of making fire by impact and friction.
These two methods, although different materials, methods are different, but both belong to the range of friction fire. This primitive method of making fire was once popular among many peoples.