Scientists believe that modern humans first appeared in southern Africa's Botswana 200,000 years ago.
It was, however, a huge, widespread swamp at that time.
About 15 to 20 separate species of early humans are currently recognized by the majority of scientists.
The location of the Kenyan Rift Valley, where the oldest known stone tools were discovered, is most likely in Eastern Africa.
Long before the modern humans known as Homo sapiens originated on the same continent, the first humans initially appeared in Africa about two million years ago.