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]
Africa Africa is the world's second largest and second most-populous continent (the first being Asia in both categories). At about 30.3 million km2 (11.7 million squareÂ miles) including adjacent islands, it covers 6% of Earth's total surface area and 20% of its total land area.[3] With 1.2 billion people[1] as of 2016, it accounts for about 16% of the world's human population. The continent is surrounded by the Mediterranean Sea to the north, the Isthmus of Suez and the Red Sea to the northeast, the Indian Ocean to the southeast and the Atlantic Ocean to the west. The continent includes Madagascar and various archipelagos. It contains 54 fully recognised sovereign states (countries), nine territories and two de facto independent states with limited or no recognition.[4] The majority of the continent and its countries are in the Northern Hemisphere, with a substantial portion and number of countries in the Southern Hemisphere.