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Oceans set stage for human evolution

Temperature changes off the coast dried out East Africa 2 million years ago

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5:10pm, February 18, 2012

VANCOUVER — Scientists may now be able to explain one of the key events that shaped human history: why East Africa got drier starting around 2 million years ago, with forests giving way to grasslands on which Homo could further evolve. Ocean temperature changes, especially the arrival of a strong warm/cool difference along the equator in the Indian Ocean, could have triggered the change.

“Those gradients are responsible for shifting rainfall towards or away from East Africa,” said Peter deMenocal, a paleoclimatologist at the Lamont-Doherty Earth Observatory in Palisades, N.Y. He presented new details about his idea on February 17 at the annual meeting of the American Association for the Advancement of Science.

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