Trade was the key to the emergence of organized communities in the savanna portions of Nigeria. Prehistoric inhabitants adjusting to the encroaching desert were widely scattered by the third millennium BC, when the desiccation of the Sahara began.
The establishment of trade networks facilitated the growth of organized communities in the Nigerian savanna areas. The early inhabitants who were coping with the encroaching desert were dispersed widely by the third millennium BC, when the Sahara started to shrink.