Originated from history, it is conceivable that the prehistoric human mind is very simple, which can not be expressed in a particularly realistic way on handicrafts, and can only be expressed in abstract and simple patterns. With the passage of time and the improvement of technology, decorative patterns began to become more complicated. Now people's ideological emancipation is also allowed, so you can see both realistic works and abstract works. It's so simple to copy downstairs, isn't it?