Connections to the World. Despite the apparent barrier created by the Sahara Desert, West Africa has been connected to the Mediterranean and lands to the east for more than a thousand years. Although no surviving written documents state exactly when trade exchanges began across the Sahara Desert, historians and archaeologists have found evidence that the kingdom of Ghana was becoming an important commercial center by the year 300. North African coins dating from that period have been found in West Africa, and historians have found proof that some camelcaravan routes from North Africa to the Sahel were established around the same time. By the year 400 more-extensive travel had resumed between West Africa and Egypt. This connection had existed much earlier, when the Sahara was more of a wetland than a desert before 2500 B.C.E., but the southern movement of the desert had...