On the horizon

News from the natural world.

Following the corn flow

Corn was first domesticated in Mexico about 9,000 years ago, but the speed and direction of its spread through the Andes remains a mystery.

Now an international team of scientists has found evidence that maize was grown and processed in Peru between 3,600 and 4,000 years ago - roughly 1,000 years earlier than previous excavations had shown.

The team, led by the Smithsonian Institution's Linda Perry, excavated a house in the southern Peruvian highlands that contained tiny, fossilized particles of maize. Scientists also found arrowroot, which grows in the Amazon rain forest, and not at the altitude where the house was excavated. The arrowroot may be one of the earliest examples of trade between highland and lowland regions that would become a hallmark of later, more sophisticated, Andean civilizations.

The results appear in Thursday's issue of the journal Nature.

Sagebrush sends a warning signal

Move over Paul Revere - meet Atemisia tridentata, alias sagebrush.

Biologists at Cornell University have found that when predators munch on the shrub, it releases volatile organic compounds into the air, warning nearby plants of danger. The scientists found that wild tobacco plants can detect the compounds and begin to "prime" their own natural defenses against predators. The tobacco plant won't actually activate its defenses until it's attacked; the effort is too costly in energy and nutrients for false alarms. But the priming does allow it to respond more quickly to attack when it happens.

The scientists aren't sure how this plays out in the real world: tobacco and sagebrush typically live in different ecosystems, and the two plants attract different types of predators. But their experiments in the greenhouse and in the field using predators specific to each plant, showed that some form of biochemical danger signal was passing from sage to tobacco. Their results appeared in a recent issue of the journal Oecologia.

Gazing at a soon-to-explode star

Astronomers are keeping a close eye on a galaxy some 440 million light years away for the appearance of a supernova - the explosion of a massive star.

The supernova watch was triggered when NASA's Swift satellite detected an unusual burst of gamma rays, said to be the most distant and powerful cosmic explosions known. Ordinarily, these bursts are short-lived - up to 10 seconds long. But the burst Swift detected was unique - it was relatively dim and lasted for almost half an hour. Astronomers in Italy have been watching the region using the European Southern Observatory's Very Large Telescope in Chile and find that it's growing brighter optically and boasts changes in its chemical signatures that point to an emerging supernova.

Professional astronomers already are preparing to train the Hubble Space Telescope, radio telescopes, and the Chandra X-ray Observatory on the object. If the supernova idea is correct, astronomers add that the event should be visible to amateur astronomers using a 16-inch telescope or larger under dark skies. For the celestial coordinates for the object, visit: www.nasa.gov/mission_pages/swift/bursts/oddball_burst. html.

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