Africa is considered by most paleoanthropologists to be the oldest inhabited territory on Earth, with the human species originating from the continent. During the middle of the twentieth century, anthropologists discovered many fossils and evidence of human occupation perhaps as early as 7 million years ago. Fossil remains of several species of early apelike humans thought to have evolved into modern man, such as Australopithecus afarensis (radiometrically dated to approximately 3.9–3.0 million years BC), Paranthropus boisei (c. 2.3–1.4 million BC) and Homo ergaster (c. 600,000–1.9 million BC) have been discovered.The Ishango bone, dated to about 25,000 years ago, shows tallies in mathematical notation. Throughout humanity's prehistory, Africa (like all other continents) had no nation states, and was instead inhabited by groups of hunter-gatherers such as the Khoi and San.
At the end of the Ice Ages, estimated to have been around 10,500 BC, the Sahara had again become a green fertile valley, and its African populations returned from the interior and coastal highlands in Sub-Saharan Africa[citation needed]. However, the warming and drying climate meant that by 5000 BC the Sahara region was becoming increasingly dry and hostile. The population trekked out of the Sahara region towards the Nile Valley below the Second Cataract where they made permanent or semi-permanent settlements. A major climatic recession occurred, lessening the heavy and persistent rains in Central and Eastern Africa. Since this time dry conditions have prevailed in Eastern Africa, and increasingly during the last 200 years, in Ethiopia.
The domestication of cattle in Africa preceded agriculture and seems to have existed alongside hunter-gathering cultures. It is speculated that by 6000 BC cattle were already domesticated in North Africa.[23] In the Sahara-Nile complex, people domesticated many animals including the pack ass, and a small screw horned goat which was common from Algeria to Nubia.
The neolithic revolution, the domestication of plants is thought to have occurred independently in three different locations, namely, the Ethiopian highlands, the Sahel and West Africa. The first known example of the domestication of plants for agricultural purposes on the continent occurred in the Sahel region circa 5000 BC, when sorghum and African rice began to be cultivated. Around this time, and in the same region, the guinea fowl became domesticated.
In the year 4000 BC the climate of the Sahara started to become drier at an exceedingly fast pace.[24] This climate change caused lakes and rivers to shrink significantly and caused increasing desertification. This, in turn, decreased the amount of land conducive to settlements and helped to cause migrations of farming communities to the more tropical climate of West Africa.
