What does the tendency of abstraction and symbolization in rock paintings mean?

The appearance of the tendency of abstraction and symbolization in rock paintings indicates the imminent rise of abstract patterns in Neolithic age, and the painted gravel in Azhili cave is an obvious sign. However, the use of these gravels remains a mystery. At present, there are at least three different explanations. Some people think that this is a tool of witchcraft or divination. Some people think that it is a symbol of primitive notes and has the embryonic form of words; Others put forward a hypothesis that this is the earliest currency of mankind, which is used to replace an intermediate in barter.