Sub-Saharan Africa

Sub-Saharan Africa is, geographically, the area of the continent of Africa that lies south of the Sahara Desert. Politically, it consists of all African countries that are fully or partially located south of the Sahara (excluding Sudan, even though Sudan sits in the Eastern portion of the Sahara desert). It contrasts with North Africa, which is considered a part of the Arab world. Somalia, Djibouti, Comoros, and Mauritania are geographically part of Sub-Saharan Africa, but also part of the Arab world.

The 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.

Sahara

The Sahara (Arabic: الصحراء الكبرى‎, aṣ-ṣaḥrāʾ al-kubrā , 'the Greatest Desert') is the largest hot desert and third largest desert after Antarctica and the Arctic worldwide. Its surface area of 9,400,000 square kilometres (3,600,000 sq mi)—including the Libyan Desert—is comparable to the respective land areas of China or the United States. The desert comprises much of the land found within North Africa, excluding the fertile coastal region situated against the Mediterranean Sea, the Atlas Mountains of the Maghreb, and the Nile Valley of Egypt and Sudan. The Sahara stretches from the Red Sea in the east and the Mediterranean in the north, to the Atlantic Ocean in the west, where the landscape gradually transitions to a coastal plain. To the south, it is delimited by the Sahel, a belt of semi-arid tropical savanna around the Niger River valley and Sudan Region of Sub-Saharan Africa. The Sahara can be divided into several regions, including the western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Aïr Mountains, the Ténéré desert, and the Libyan Desert. Its name is derived from the plural Arabic language word for desert (صحارى ṣaḥārā [ˈsˤɑħɑːrɑː]).

Africa

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 Earth's total surface area and 20.4 percent of its 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 contains 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 amongst all the continents; the median age in 2012 was 19.7, when the worldwide median age was 30.4.Algeria is Africa's largest country by area, and Nigeria 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 earliest hominids and their ancestors, as well as later ones that have been dated to around seven million years ago, including Sahelanthropus tchadensis, Australopithecus africanus, A. afarensis, Homo erectus, H. habilis and H. ergaster – with the earliest Homo 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.