Twelfth- and Thirteenth-Century Explorers. Though knowledge of West Africa had been carried along trans- Saharan trade routes to North Africa, and from there to Europe for hundreds of years, West Africa was not explored by sea until the twelfth century, when Arabic sources recorded several attempts to sail along its coastline. Writing in 1154, Moroccan geographer al-Idrisi told about some Muslim adventurers who set off from Lisbon, Portugal and may have reached the Canary Islands, which lie off the Atlantic coast from the southwestern corner of Morocco. The thirteenth-century historian Ibn Sa'id said that Muslims explored the West African coast during the twelfth century, probably in search of a good source for the "tunny fish" that were a main food for Moroccans. North Africans, however, did not put much capital or effort into such seafaring ventures because the trans-Saharan trade route...