re: First human ancestors came from Europe not Africa 7.2 million-year-old fossils indicate

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The Sahara was not desert until fairly recently geologically. It was grassland during the last ice age and for a while afterwards. Desertification did not become widespread until the early Egyptian civilizations had begun building mud brick mastabas. In fact, there was still enough water to traverse the Sahara on horseback as recent as the Roman wars with Carthage.

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Before the great desert was born, North Africa had a moister, semiarid climate. A few lines of evidence, including ancient dune deposits found in Chad, had hinted that the arid Sahara may have existed at least 7 million years ago. But without a mechanism to explain how it emerged, few scientists thought that the desert we see today could really be that old. Instead, most scientists argue that the Sahara took shape just 2 to 3 million years ago. Terrestrial and marine evidence suggest that North Africa underwent a period of drying at that time, when the Northern Hemisphere started its most recent cycle of glaciation.

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