Africa is the world’s second-largest and second-most-populous continent. At about 30.2 million km2 (11.7 million sq mi) including adjacent islands, it covers six percent of the Earth’s total surface area and 20.4 percent of the total land area. With 1.1 billion people as of 2013, it accounts for about 15% of the world’s human population. The continent is surrounded by the Mediterranean Sea to the north, both the Suez Canal and the Red Sea along the Sinai Peninsula to the northeast, the Indian Ocean to the southeast, and the Atlantic Ocean to the west. The continent includes Madagascar and various archipelagos. It has 54 fully recognized sovereign states (“countries”), nine territories and two de facto independent states with limited or no recognition. Africa’s population is the youngest among all the continents; 50% of Africans are 19 years old or younger. Algeria is Africa’s largest country by area, and Nigeria is the largest by population. Africa, particularly central Eastern Africa, is widely accepted as the place of origin of humans and the Hominidae clade (great apes), as evidenced by the discovery of the earliesthominids and their ancestors, as well as later ones that have been dated to around seven million years ago, includingSahelanthropus chadensis, Australopithecus africanus, A. afarensis, Homo erectus, H. habilis and H. ergaster – with the earliestHomo sapiens (modern human) found in Ethiopia being dated to circa 200,000 years ago. Africa straddles the equator and encompasses numerous climate areas; it is the only continent to stretch from the northern temperate to southern temperate zones. From Wikipedia, the free encyclopediaThe Sahel is the transitional zone between the Sahara and the tropical savanna (the Sudan region) and forest-savanna mosaic to the south. Since probably 3500 B.C.E, 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 River 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. The use of the term has been criticized because it refers to the South only by cartography conventions and projects a connotation of inferiority; a vestige of colonialism, which some claim, divided Africa into European terms of homogeneity.From Wikipedia