With any large construction project, organizing the work is half the battle. Contracts must be signed, materials must be delivered on time and, when lots of extra labor is involved, care and feeding of workers must be attended to.
The great houses of the Chaco, the indigenous people who inhabited north-central New Mexico a thousand years ago, were vast construction projects. They were sprawling masonry structures, some of them five stories tall with hundreds of rooms. Archaeologists hypothesize that building of the great houses, from the 9th to the 12th centuries, required the importing of laborers as well as food for them.
Now, researchers are lending credence to this theory. Analyzing corn cobs excavated from great houses at Pueblo Bonito, the largest of the sites in Chaco Canyon, they have found evidence that the corn was hauled in from distant sites.
Corn, or maize, was a staple for these people, but with cool temperatures and relatively little rainfall, conditions for growing it in the canyon were less than ideal. Conditions were more favorable in other parts of the region.
The researchers, from the United States Geological Survey, the University of Colorado and other institutions, analyzed the ratio of strontium isotopes and other trace elements in the cobs, which provide a kind of chemical signature of the soil that grew the maize. They compared this data with similar analyses of soils from several sites in the region.
Their conclusion, reported in The Proceedings of the National Academy of Sciences, is that Pueblo Bonito maize came from elsewhere, notably a settlement about 50 miles to the west that was an agricultural center.
Seeing in Ultraviolet
Bats may not be blind, but their vision, overshadowed as it is by their echolocating abilities, is hardly something to boast about. Except, perhaps, in the case of a certain nectar-drinking bat that researchers say has a special ability: it can see ultraviolet light.
Scientists from Germany and Guatemala were interested in the animal, Glossophaga soricina, also known as the long-tongued bat, because it pollinates certain tropical flowers that reflect light in the ultraviolet range. So they conducted behavioral experiments on several of the bats to determine their sensitivity to light at certain wavelengths.
Their results, reported in the journal Nature, show that, like most other mammals, the bats are colorblind. But unlike most other mammals except a few rodents and marsupials, they are sensitive to light at short wavelengths, with a peak sensitivity at a wavelength of 365 nanometers, in the ultraviolet.
The bats had another peak sensitivity in the green portion of the visible spectrum. Additional tests showed that these two peaks are a function of a single receptor in the eye. This single-receptor system is so far unique among mammals that can perceive ultraviolet; rodents, for example, have a separate receptor for ultraviolet.
The researchers suggest that the bats' vision may be an adaptation that helps it find ultraviolet-reflecting flowers at twilight. At dusk the light spectrum shifts to shorter wavelengths; without ultraviolet vision, the flowers would not stand out.
Asteroids large and small pass Earth all the time, but the small one that whizzed by on Sept. 27 was special: it is the closest one that has been documented.
The rock, estimated to be 10 to 20 feet in diameter, came within about 55,000 miles of Earth. It was discovered by astronomers with Minor Planet Research, an organization that collaborates with the Lowell Observatory's near-Earth object search program in Arizona. The asteroid beat the previous record holder, a larger 1994 rock, by about 10,000 miles.
Of course, small rocks like these hit Earth occasionally, too. But they are not big enough to cause widespread damage.Continue reading the main story