Many elements of the traditional account, especially the early parts, were clearly mythical. In the 1920s, Gu Jiegang and other scholars of the Doubting Antiquity School noted that the earliest figures appeared latest in the literature, and suggested that the traditional history had accreted layers of myth. Noting parallels between the accounts of the Xia and Shang, they suggested that the history of the Xia was invented by the Zhou to support their doctrine of the Mandate of Heaven, by which they justified their conquest of the Shang. Some even doubted the historicity of the Shang dynasty.