"Copy from one, it's plagiarism; copy from two, it's research. "
In China historians have found out a lot about the early Chinese dynasties from the written documents left behind. From the Shang Dynasty most of this writing has survived on bones or bronze implements. Markings on turtle shells (used as oracle bones) have been carbon-dated to around 1500 BC. Historians have found that the type of media used had an effect on what the writing was documenting and how it was used.