He repeatedly challenges formulaic ideas about causality, linearity as a model of change, and the cultural factors affecting innovation…. Ehret has written a fabulous African history book, furthering a genre far from the seemingly ubiquitous slavery studies and trendy colonial social history".[2] Peter Robertshaw in the Journal of the Royal Anthropological Institute, offers a more measured conclusion: "Ehret has produced a remarkably coherent and detailed history which should spur further research".[3]