Osteomancy

Osteomancy is divination by bone, and the single name covers two quite distinct procedures often conflated. In the first, a bone is heated until it cracks, and the resulting network of cracks is read. This is the celebrated method of the Chinese oracle bones of the Shang dynasty (roughly the second millennium BCE): diviners applied heat to the shoulder-blades of oxen and the plastrons of turtles, interpreted the cracks that formed as the gods' or ancestors' answer to a posed question, and then, crucially for history, inscribed the question and often the outcome beside the cracks. These inscriptions constitute the earliest substantial body of Chinese writing yet known, and they are a primary source for the religion, kingship, and language of the Shang, making this form of osteomancy one of the most historically consequential divinatory practices in the world. (The related practice of reading the cracks in heat-treated turtle shells is sometimes distinguished as plastromancy.)

In the second, quite different procedure, the form of a bone is read, most familiarly the wishbone or, in the practice known as scapulimancy in its non-heated form and in many pastoral cultures, the natural markings and shape of an animal's shoulder-blade after it is cleaned. Osteomancy thus reflects a widespread intuition that the bodies of sacrificed or slaughtered animals, and especially their bones, carry legible signs of the divine will.

Reading bone by heat is attested across a very wide area, from northern China through Central Asia to the subarctic Americas, and the two best documented cases sit at opposite ends of that range.

The Chinese material is the richest divinatory archive in existence. Shang diviners applied heat to prepared ox scapulae and turtle plastrons, read the cracks that resulted, and then inscribed the question, and often the outcome, onto the bone itself. The bones were recognised for what they were only in 1899, after fragments had been circulating as dragon bones in the medicine trade, and excavation at Anyang recovered them in enormous numbers. They give direct access to the concerns of a Bronze Age court: harvests, childbirth, illness, campaigns and the disposition of the ancestors.

The other case produced an argument that has outlived its context. Ethnographers described hunting peoples in subarctic Canada heating a caribou shoulder blade and reading the cracks to decide where to hunt. A paper published in the 1950s proposed that the practice functioned as a randomising device: by removing the choice from human judgement it prevented hunters from returning repeatedly to grounds that had recently been successful, which would deplete them and make the game wary.

Whether that explanation is correct has been debated since, and it is a reminder that a practice may do something useful for reasons unconnected to what its practitioners say it does.