Why did Shang people carve words on tortoise shells or cattle shoulder blades?

In Shang Dynasty in China, a popular character was Oracle Bone Inscriptions. In fact, Oracle Bone Inscriptions used it in the late Shang Dynasty and the Western Zhou Dynasty in ancient China, carving words on tortoise shells or cattle shoulder blades. Many of them are grotesque, and people still don't know what they mean. So what is the reason for engraving on tortoise shells or cattle shoulder blades?

In fact, we can know from the remaining documents that people in the Zhou and Shang Dynasties used tortoise shells for divination. Due to the feudal psychology at that time, people carved characters on tortoise shells, which can predict whether a thing is fierce or auspicious. There is a saying in Zuo Zhuan: The tortoise looks like it, which counts. The so-called divination is divination according to the change of numbers. It is recorded in literature that people began to have this behavior in Shang Dynasty. In addition, before moving the capital, Zhou Wuwang used tortoise shells to calculate obsolescence and auspiciousness. So at that time, not only the people believed in divination, but also the emperor believed in tortoise shell divination.

In the process of modern archaeology, Chinese archaeologists have discovered many Oracle bones with tortoise shells and cattle shoulder blades, leaving us with many Oracle Bone Inscriptions, and at the same time, many Oracle bones have been unearthed in Shanxi, Shaanxi, Beijing and other places in China, which has also aroused many historians' strong interest in Oracle bones. According to the unearthed conditions, we can find that Oracle Bone Inscriptions has certain similarities. This shows that the role of Oracle bones and cattle scapula has always been the same, and the method of divination is inherited and not changed at any time, but there are still many Oracle Bone Inscriptions we don't know. I hope I can understand later.