Word: rats
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Nausea? Little wonder. The glistening balls mistaken for a snack that day in Nevada were later identified as pack-rat middens -- globs of crystallized pack-rat urine containing sticks, plant fragments, bones and animal dung. Still, while the middens failed to make the grade as cuisine, they have begun to excel in another role -- as a kind of natural time capsule...
...Pack-rat middens are found in arid regions of North and Central America and take shape when the acquisitive rodent, like its human namesake, collects and carries home virtually all the trash it can find. It piles the debris in its den, where it becomes saturated with urine. As the urine evaporates in the dry climate, it crystallizes, gradually enveloping the collection and forming a large, hard clump. Protected from the elements, the pack rat's trophies, like insects entombed in amber, are preserved for millenniums...
...pack-rat midden is a snapshot of the flora and fauna existing within about 50 m ((164 ft.)) of the midden at the time it was accumulating," explains Peter Wigand, a paleoecologist at the University of Nevada's Desert Research Institute. Scientists can pin down the approximate time the snapshot was taken by radiocarbon dating of a preserved twig or fecal pellet; the technique can date specimens that are more than 40,000 years old. And by studying middens of different vintages in the same area, researchers can in effect create a movie from a sequence of snapshots, showing changes...
Middens can reveal changes in the heavens as well as on earth. That was demonstrated by hydrologist Fred Phillips of the New Mexico Institute of Mining and Technology, who checked an ancient pack-rat midden for evidence of cosmic-ray bombardment of the earth. He knew that highly energetic cosmic-ray particles create the radioisotope chlorine 36 when they strike argon atoms in the atmosphere, and that the isotope finds its way into plants and the urine of mammals, including the pack rat...
...rat," Gravano said...