Little is known about the original inhabitants of Côte d'Ivoire. Historians believe that they were all either displaced or absorbed by the ancestors of the present inhabitants. The first recorded history is found in the chronicles of North African Muslim traders, who, from early Roman times, conducted a caravan trade across the Sahara in salt, slaves, gold, and other items. The southern terminals of the trans-Saharan trade routes were located on the edge of the desert, and from there supplemental trade extended as far south as the edge of the rain forest. The more important terminals—Djenné, Gao, and Timbuctu—grew into major commercial centers around which the great Sudanic empires developed. By controlling the trade routes with their powerful military forces, these empires were able to dominate neighboring states. The Sudanic empires also became centers of Islamic learning. Islam had been introduced into the western Sudan by Arab traders from North Africa and spread rapidly after the conversion of many important rulers. From the eleventh century, by which time the rulers of the Sudanic empires had embraced Islam, it spread south into the northern areas of contemporary Ivory Coast.