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Keeping an eye on what was once afoot.

Keeping an eye on what was once afoot

One would think that remote sensing techniques would have little chance of detecting traces of prehistoric humanity in the land around the Arenal volcano in northwestern Costa Rica. The region, soaked by high rainfall, is covered by a lush tropical forest. And because the Indians who inhabited the area 4,000 to 500 years ago wre few in number, their roads and villages were small and far between. Moreover, Arenal has erupted more than 10 times in the last 4,000 years, each time smothering the region with layers of ash.

But in spite of these obstacles, anthropologist Payson D. Sheets at the University of Colorado in Boulder and Tom Sever, NASA's only anthropologist, have shown that conventional remote sensing methods do indeed work in such an environment. They've seen their way clear to identify 62 archaeological sites, including villages, campsites and cemeteries. The researchers' most impressive accomplishment, however, is in using aerial black-and-white and infrared photographs to detect half-meter-wide buried footpaths, some of which have been traced for a few kilometers.

During the time they had been used, these paths were eroded down into trenches. Later, they were filled in with sediments that were better suited for plant growth than were the surrounding soils. As a result, grass growing above the paths is slightly greener than the grass on either side, a difference detected by the infrared data. And where a faint depression at the surface mirrors the shape of the foothpath below, the researchers can detect shadows with the black-and-white photos. In nearly all cases, excavations have corroborated their interpretations of the remote sensing data.

The discovery of the footpaths is enabling Sheets and Sever to take a big step toward understanding the societal structure, rituals and resource use of the people who made them. "The paths tell us where to excavate and where to follow, literally in their footsteps, to the places that were of interest and of value to them," says Sheets. "And for the first time we can relate sites to other sites." Heavily used footpaths between a high-status cemetery and a spring, for example, indicate that people spent a considerable amount of time at the graveyard. Sheets hopes the paths will connect this cemetery to a village so they can find out what kinds of people ranked burial in the cemetery.
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Title Annotation:remote sensing used to identify archaeological sites in Costa Rica
Author:Weisburd, Stefi
Publication:Science News
Date:Nov 22, 1986
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