In Shang and Zhou Dynasties, why was tortoise shell mainly used for divination?

This is mainly related to the nature of turtles. As we all know, the main purpose of China's ancient divination is nothing more than bad luck. The image of a turtle was originally an auspicious image in ancient China. Among the four great beasts in China, the prototype of Xuanwu is based on the change of tortoise. Besides, the tortoise was a symbol of longevity in the eyes of the ancients. This is also one of the reasons why the ancients chose turtles to perform instrument divination when choosing instruments to be used for divination.

Another point is related to the structure of the tortoise itself. The ancients in China thought that it was meaningful to have turtle lines on the back of the turtle, but there were three squares in the middle of the turtle shell. The ancients thought that these three squares represented three talents of heaven and earth, and the 24 squares next to them represented 24 mountains. Of course, there is also a checkered turtle pattern representing ten days of dryness. For the bottom 12 lattice, in the eyes of the ancients, it represents 12 earthly branch. Therefore, a small turtle shell contains endless mysteries. In the eyes of the ancients, these specifications correspond to the stars in the sky. This is also the reason why the ancients chose tortoise shells when choosing divination tools.

Another point is related to the habits of turtles. There is a folk proverb in China that a turtle sweats on his back and takes an umbrella when he goes out, which shows that the turtle has the magical ability to predict the weather. So the ancients thought that turtles could predict the future. Therefore, when choosing tools, people usually choose tortoise shells, because the prediction accuracy is higher. This was also discovered by the ancients in long-term observation.

Of course, this is only part of the reason why tortoise shells were chosen as divination tools in ancient times. In fact, whatever the reason, it is a kind of luck and an effect. To tell the truth, for divination, sometimes you don't believe it, and the feeling is true. Sometimes you believe it, and it's not scientific. Therefore, when we look at divination, we can keep a more positive view. If we don't believe it, we can't believe it.