Africa did not give birth to the ancestors of monkeys, apes and humans as is often believed, new research suggests.
Instead the earliest "anthropoids" colonised Africa from Asia, it is claimed.
New fossils discovered in central Libya and dating back 39 million years contain a surprising variety of species, say scientists.
They include three distinct families of anthropoid primates that lived in North Africa at about the same time.
Their sudden appearance can either be explained by a striking gap in the African fossil record, or colonisation from another continent.
Writing in the journal Nature, the experts said they believed migration from Asia to be the most plausible theory.
Lead researcher Dr Christopher Beard, from the Carnegie Museum of National History in Pittsburgh, US, said: "If our ideas are correct, this early colonisation of Africa by anthropoids was a truly pivotal event - one of the key points in our evolutionary history.
"At the time, Africa was an island continent; when these anthropoids appeared, there was nothing on that island that could compete with them.
"It led to a period of flourishing evolutionary divergence amongst anthropoids, and one of those lineages resulted in humans.
"If our early anthropoid ancestors had not succeeded in migrating from Asia to Africa, we simply wouldn't exist."