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1 .This is Scientific American 60-Second Science. I'm Cynthia Graber. Got a minute?
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2 .The Spanish arrival in South America changed many things, including, it seems, even the Peruvian coastline.
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3 .In dry northwestern Peru, unusual 19-mile-long sandy coastal ridges were formed through tectonic activity, El Ni?o storms and natural sediment deposit.
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4 .The nine ridges still standing appear to have formed from 5,100 years ago until about 400 years ago.
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5 .And they're topped with deposits of shells, rocks from fire pits and other human artifacts.
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6 .Scientists studying the region found that the shells are from mollusks and barnacles, and primarily of species still fished there today.
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7 .They thus concluded that the shells were left by native communities who long called the region home.
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8 .The researchers also found that the clamshell and fire deposits stabilized the ridges and protected them from erosion.
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9 .No such stable ridges exist along the coast from the past 400 years, after the local people died from disease or war, or were pushed inland.
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10 .Any incipient ridges since were easily toppled by wind and storms.
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11 .The research is in the Proceedings of the Natural Academy of Sciences.
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12 .Visitors now see what they may think is a natural landscape.
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13 .But its formation depended on thousands of years of human activity.
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14 .Thanks for the minute, for Scientific American 60-Second Science. I'm Cynthia Graber.
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