Africa reached the peak of its power around the year 2050 BC when the middle Kingdom of Egypt was at its most powerful.

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One of Dr Weiss's former students, Sarah Parcak, of Cambridge University, presented data to the meeting on how a third period of cooling and drying, 4, 200 years ago, destroyed the Old Kingdom of Egypt.

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Of course, rain-fed agriculture is even more vulnerable to climate change than the irrigated variety, as Ms Parcak's Cambridge colleague Lauren Ristvet showed the conference with her study of northern Syria during the same period as the fall of Egypt's Old Kingdom.

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Over the past three months, the small North African kingdom has seen regime change roil two of its neighbors, Tunisia and Egypt, and a third Libya descend into civil war.

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The dealer trusted him enough to produce a crate of what he said were artefacts more than 3, 000 years old, from Middle Kingdom Egypt.

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