Scientists say the sexually precocious offspring of farmed Atlantic salmon threaten the survival of genetically distinct wild stocks. New research suggests the young produced by fish escaping from salmon farms are four times more successful at breeding in rivers than native fish.

Scientists believe they may have cracked the enigma of a rampant neurological disease that causes paralysis, dementia and death in the Chamorro people of the Pacific. A new study correlates rates of bat-eating practiced by the people, with incidence of the disease.

The virus in chimpanzees believed to have been transmitted to humans to become HIV-1—the virus that causes AIDS—didn't start its life in chimps. Instead, separate viruses jumped from different monkey species into chimps, where they recombined to form a hybrid virus, according to a new study.

Over the course of their migration from Panama to Canada, New World Catharus thrushes spend twice as much energy slurping worms, munching snails, and heating their bodies than they do actually flapping their wings in flight, according to new research.

As three separate missions journey to Mars this month to search for signs of life, one scientist claims that he already proved there's life on the red planet—in 1976.

Fossils recovered from Ethiopia lend archaeological credence to the theory that modern humans evolved in Africa before spreading around the world. Owing to the mix of primitive and modern features exhibited by the skulls, scientists assigned them to a new subspecies of Homo sapiens they named Homo sapiens idaltu.

A National Geographic archaeological expedition to Iraq—the first survey of the country's antiquities beyond Baghdad since the April war—reports that although bombs spared most sites and treasures, some ancient locations have been seriously damaged by looting or long-term neglect. In many places hundreds of people were openly making illegal excavations.

For every fourth or fifth generation of monarch butterflies that summer in the U.S. east of the Continental Divide, the pull of high-altitude Oyamel fir forests in central Mexico is irresistible. Now scientists have discovered that they make the 2,000-mile (3,200-kilometer) flight with the help of an internal clock.

Radio-tagged tarantulas are being used by researchers to monitor the threatened rain forests of Belize. Each spider emits a unique call sign, allowing it to be identified with a hand-held scanner even when it is in its lair. The health of the arachnids indicates the health of the habitat.

The Earth's climate is changing—raising temperatures, disrupting rain patterns, and stoking diplomatic rows between the nations. But for the world's plant kingdom the recent changes have been well received. New research finds that vegetation is increasing around the globe. Is that good or bad news?

The source of SARS has mystified medical experts. Some believe it evolved naturally in humans. Others say it must have jumped from an animal, maybe a chicken or an exotic bird. But one group of British scientists suggests a more far-out origin: space.

SARS has created more turbulence for the airline industry than 9/11 and the Iraq War combined, according to an airline trade group. But Traveler Editor in Chief Keith Bellows says media hype has overstated the risk to travelers and that deals in Toronto and Beijing abound.

Humans may someday be able to scuttle up walls, scamper across ceilings, and scurry out windows with the agility of a startled gecko in the tropical night—thanks to a new adhesive tape that mimics the lizard's sticky feet.

Strong evidence of water on Mars has propelled NASA to launch rovers to investigate. Robots destined for two different locations are tested in the "sandbox," at NASA's Jet Propulsion Laboratory, which simulates the Martian landscape. Science correspondent Chad Cohen gets a Martian preview tonight on our U.S. cable television program National Geographic Today.

First there was Dolly, the sheep. Now, scientists at the University of Idaho have successfully cloned a mule. Born on May 4, Idaho Gem is the first member of the horse family to be cloned.