Why Did Humans Spread Out of Africa?
Humans evolved in Africa and lived only there for as long as 2, or possibly 3, million years. So scientists wonder what finally triggered the first human migration out of Africa (a movement that coincided with the spread of early human populations throughout the African continent). The answer to this question depends, in part, on knowing exactly when that first migration occurred. Some studies claim that sites in Asia and Europe contain crude stone tools and fossilized fragments of humanlike teeth that date from more than1.8 million years ago. Although these claims remain unconfirmed, small populations of humans may have entered Asia prior to 1.7 million years ago, followed by a more substantial spread between 1.7 million and 1 million years ago. The first major habitation of central and western Europe, on the other hand, does not appear to have occurred until between 1 million and 500,000 years ago. By the time of the earliest humans, the worlds continents were in essentially the same
