For nearly a thousand years, camel caravans plied the trackless sands of the western Sahara, a barren landscape where arid conditions and searing sun conspire against crops, trees, and even desert grasses. Traveling from well to well, merchants transported the products of West Africa--gold, ivory, salt, and slaves--to the northern reaches of the continent, where they would exchange them for glass, ceramics, and precious stones brought to North Africa from the wider Mediterranean world.