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Geologists collected about 150 samples of sediment from the site in 2007. To come up with an age, they used a technique known as paleomagnetic dating, which takes advantage of the flip-flop of Earth’s magnetic field every several hundred thousand years.

The tools were not too far from where the bones of Turkana Boy _ the most complete skeleton of a prehistoric human _ were unearthed in 1984.

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Online:

Nature journal: www.nature.com/nature

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