Word: layers
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...team led by University of Kentucky archaeologist Tom Dillehay discovered indisputable traces there of a human settlement that was inhabited between 12,800 and 12,300 years ago. Usually all scientists can find from that far back are stones and bones. In this case, thanks to a peat layer that formed during the late Pleistocene era, organic matter was mummified and preserved as well...
...fellow scientists has been a battle. Guidon's conclusions have been greeted with skepticism by many archaeologists. One problem, explains Randall White of New York University, is that the "tools" from the deepest levels at Pedra Furada are mixed with naturally fractured river gravel. This suggests that the geological layer was not laid down in an orderly way. The stone flakes could easily have been churned together with much older river rock before settling. Moreover, they might not be human-made at all; the artifacts themselves could have formed by natural erosion...
...evidence for communal living was the fact that groups of nests were found in a single layer of sediment, implying that they were all built in the same year. Beyond that, the nests were spaced an average of 23 ft. apart -- about the size of an adult maiasaur. Birds often do the same thing, laying their eggs close enough together for maximum mutual protection, yet far enough apart so that they can move easily past their neighbors. Inside the nests, Horner found lots of tiny eggshell fragments. If the baby maiasaurs had simply hatched and wandered off to fend...
Production of cfcs -- the chemicals that attack earth's precious atmospheric ozone layer and are being phased out by international agreement -- is falling even faster than expected. That's the good news. The bad news is that cfcs already released are still drifting up through the atmosphere. New satellite data, reported in the current Nature, show that ozone levels over some northern parts of Canada, Scandinavia and Russia were 10% lower this winter than they were just one year...
Sure, if you are a popcorn nut, you know that some types of corn are great poppers and others aren't. But do you know why? Have you assessed the thermal diffusivity of the pericarp, the kernel's tough outer layer? Have you analyzed the starch content of the endosperm, the inner, meaty layer? Have you compared the ratios of expanded to original volumes of various kernels? If so, you would know that the pericarp in popcorn has more densely packed fiber than that of ordinary corn. You'd know that starch content is less important. You needn't bother...