Out of Africa: The most important woman in history?
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Around 70,000 years ago a tribe of fully-developed, modern humans began to move towards the north east coast of Africa.
After studying the evolution of human DNA scientists have concluded that only one tribe lasted long enough outside Africa to leave a lasting legacy - and that almost all of us alive today are related to one woman, from this tribe.
There is a tiny genetic mutation in every person who isn't from sub-Saharan Africa, and scientists have tracked it back to one migration from Africa, one tribe, and one woman.
Andrew Marr's History of the World, an eight part series, is broadcast from Sunday 23 September, at 21:00 BST on BBC One.