what geographical feature limited contact between sub-saharan africa and the outside world
Sub-Saharan Africa Since probably 3500Â BCE,[4][5] the Saharan and Sub-Saharan regions of Africa have been separated by the extremely harsh climate of the sparsely populated Sahara, forming an effective barrier interrupted by only the Nile in Sudan, though the Nile was blocked by the river's cataracts. The Sahara pump theory explains how flora and fauna (including Homo sapiens) left Africa to penetrate the Middle East and beyond. African pluvial periods are associated with a Wet Sahara phase, during which larger lakes and more rivers existed.[6]
Ghana Empire The Ghana Empire (c. 700 until c. 1240), properly known as Awkar (Ghana or Ga'na being the title of its ruler), was located in the area of present-day southeastern Mauritania and western Mali. Complex societies based on trans-Saharan trade with salt and gold had existed in the region since ancient times[1], but the introduction of the camel to the western Sahara in the 3rd century A.D. opened the way to great changes in the area that became the Ghana Empire. By the time of the Muslim conquest of North Africa in the 7th century the camel had changed the ancient, more irregular trade routes into a trade network running from Morocco to the Niger river. The Ghana Empire grew rich from this increased trans-Saharan trade in gold and salt, allowing for larger urban centres to develop. The traffic furthermore encouraged territorial expansion to gain control over the different trade-routes.