A New Theory on Mad Cow
Citing circumstantial evidence, two British researchers have raised the provocative possibility that mad cow disease arose in English herds after they were given imported feed that contained remains of humans who had died of the closely related Creutzfeldt-Jakob disease.
The infection may have come from India, Pakistan or Bangladesh, they wrote in last week's issue of the journal the Lancet, because scavenging for human bones and remains is widespread in those nations. The researchers said there have been documented reports that those remains have been included in exported material used for animal feed and fertilizer that was used widely in England in the 1960s.
The researchers, Alan Colchester of the University of Kent and Nancy Colchester of the University of Edinburgh, wrote that mad cow disease is most similar to the human variant of the infection.
Many researchers have hypothesized that mad cow disease came initially from sheep infected with scrapie, a similar infection, but the Lancet paper said all experimental efforts to transmit scrapie from sheep to cows, and to create the variant called bovine spongiform encephalopathy, or mad cow disease, failed.
British dairy farmers were aggressively feeding their animals meat and bone meal in the 1960s as a way to increase milk production. The processed scraps were given to calves as young as 1 or 2 weeks old, they said, and those animals were most prone to infection from the disease.
About 150 people have died of mad cow disease, most in Britain and most after eating beef infected with the disease.
-- Marc Kaufman
Family of Rare Cheetahs Found
A team of Iranian and Wildlife Conservation Society scientists has discovered a family of rare Asiatic cheetahs and photographed them with a remote camera, the scientists announced Tuesday.
Asiatic cheetahs used to roam from the Red Sea to India, but the big cats are disappearing: Fewer than 60 now exist in all of Asia. Most live on Iran's dry central plateau.
"As a species, the cheetahs are still in dire straits in Iran, so it is extremely encouraging to see an apparently healthy family in their native habitat," said Peter Zahler, assistant director of the Wildlife Conservation Society's Asia programs.
The camera captured a mother cheetah and four cubs on Iran's isolated Dar-e Anjir Wildlife Refuge. Luke Hunter, who coordinates the society's Global Carnivore Program, said the fact that the female cheetah "has managed to raise four cubs to 6 months of age is extremely encouraging."
In the 1970s, biologists estimated that 100 to 400 cheetahs lived in Iran, but widespread poaching in the early years of the 1978 revolution, coupled with livestock grazing, have pushed them to the brink of extinction. Asiatic cheetahs disappeared from much of the Middle East a century ago, though they survived in India until 1947 and in Central Asia as late as the 1980s.
-- Juliet Eilperin
First You Swim, Then You Crawl
Fish gotta swim. Always have.
But when prehistoric fish first started dragging their way onto land around 360 million years ago, how did they get around?
New evidence suggests they did not wag their bodies from side to side, fishlike, while slithering their bellies along the ground, as many scientists had thought.
Rather, a reanalysis of fossil skeletons from these test pilots for terrestrial locomotion suggests the creatures had enough strength in their primordial limbs to hold their bodies off the ground. Thus elevated, they probably pulled themselves forward like giant inchworms, extending and contracting their two-foot-long bodies.
The long-extinct critter, named ichthyostega, was among the first to make a stab at living on land. Its home was eastern Greenland, and the fossils it left behind have been studied since the 1930s.
Scientists have presumed that the major muscles in ichthyostega's torso operated much as muscles work in fish, producing a lateral wagging motion -- probably with extra help from its four finny feet. But a new analysis by Per Erik Ahlberg of Uppsala University in Sweden and colleagues finds that the orientation of its ribs and other bones probably precluded much lateral motion.
Instead, the animal probably pulled itself forward with its front appendages and followed up with a catchup move from the rear. Alternatively, the team hypothesizes, it may have managed a primordial walking gait, with diagonally synchronized limb movements.
Whatever it was, it worked. For a while.
But after its 15 minutes of fame as the world's first documented four-legged creature, ichthyostega disappeared -- one of countless "failed experiments" in the course of evolution, the researchers eulogized in Thursday's issue of Nature.
-- Rick Weiss