Sea in culture of barbarian invaders and knowledge of geography took a backward step. In the seventh century, Isidore of Seville produced a "wheel map" in which Asia, Africa and Europe were arranged like segments in an orange, separated by the "Mare Mediterranean", "Nilus" and "Tanais" and surrounded by "Oceanus". It was not until the fifteenth century that Ptolemy's maps were used again and Henry the Navigator of Portugal initiated ocean exploration and maritime research. Encouraged by him, Portuguese navigators explored, mapped and charted the west coast of Africa and the Eastern Atlantic and this knowledge prepared the way for the great voyages
Technology, Tradition, and the State in Africa the two continents. In particular he criticises the idea that African political systems were ever feudal, believing that such a concept – while applicable to Medieval Europe – was not applicable to pre-colonial Africa. In the first chapter, entitled "Feudalism in Africa?", Goody explores the various definitions of the word "feudalism", and the manner in which it has been used to describe historical societies across both Europe and Asia, and also the manner in which social anthropologists have used it to refer to contemporary societies in Africa. He proceeds to discuss the various definitions of feudalism, and the way in