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An unlikely alliance between corn plants and wasps against herbivorous insects, reported by US scientists, could help farmers grow food with fewer pesticides. A study of the beet army worm caterpillar - a devastating pest of corn and cotton - shows that it drools a chemical called volicitin as it chews on a leaf. The chemical acts as an attractant to the wasp which stings the caterpillar and lays its eggs under the skin, providing the newly hatched larvae with a nourishing food source. The alliance between corn and wasp probably evolved by chance, according to the report in Science, and researchers are now trying to breed the same protective characteristic into domesticated cotton.

A new category of pre-historic human society, between hunter-gatherer and farmer, is suggested by US scientists who have found evidence of domestic crop cultivation about 10,000 years ago in what is now Mexico. The dating of ancient remnants of a pumpkin-like squash from Mexican caves suggest the transition between a wandering society of hunter-gatherers and a more settled village life took several thousand years, unlike the rapid change that occurred in the Near East and China, according to the report in Science.

Radioactivity from the Sellafield re-processing plant has spread through the Arctic ocean into the waters of northern Canada. The contamination, which has never before been picked up so far from Britain, is having a bigger impact on the Arctic than the Chernobyl accident, according to a study by Canadian researchers reported in New Scientist. The data, to be presented at a conference in Norway next month, show that a plume of iodine-129 has penetrated beyond Siberia at a depth of 200 metres with radioactivity "an order of magnitude greater than the background level from nuclear weapons fall-out."

The most powerful magnet in the world, which exerts a force 250,000 times as strong as the Earth's magnetic field, has been built at the Lawrence Berkeley National Laboratory in California. The magnet, made of a niobium- tin alloy, has a field strength of 13.5 tesla - 22 per cent more powerful than the previous record holder, a Dutch magnet constructed in 1995, according to New Scientist. A series of such magnets could one day be used by particle physicists to accelerate and smash particles together with unprecedented energies.

Could Chagas disease, allegedly acquired by Charles Darwin on his historic voyage in The Beagle, be one of the oldest in the world? The disease, which affects the heart and could explain why Darwin became an invalid for the last 40 years of his life, infects 18-20 million Latin Americans. Researchers in Colombia report in The Lancet that they have identified the parasite trypanosoma cruzi, the organism that caused Chagas disease in 4,000-year-old mummies from southern Peru and northern Chile. The researchers used sophisticated laboratory techniques to examine DNA from skeletal and abdominal organs of 27 mummified bodies found in the Atacama desert. They identified T Cruzi in the hearts of seven mummies and one had evidence of the parasite in four of its organsn