sentences:  Archaeological work by Rod McIntosh and Susan Keech McIntosh indicates that long-distance trade and specialized economies existed in the Western Sudan at an early date.During the 9th and 10th centuries, Berbers and Arabs built upon these pre-existing trade routes and quickly developed trans-Saharan and sub-Saharan transport networks.The successive local Muslim kingdoms developed increasing sophistication as states, their martial capacity, slave raiding, holding and trading systems.