Researchers recorded muscle activity in octopus limbs, and found that an arm generates two waves of muscle contractions that propagate toward each other. When the waves collide, they form a part-time joint.

This process occurs three times, forming a shoulder where the arm meets the body, a wrist where the suckers have grasped their food, and an "elbow" somewhere in between. The elbow typically exhibits the most movement during food retrieval.

The researchers say this is a remarkably simple and apparently optimal mechanism for adjusting the length of arm segments according to where the food item is grasped along the arm.

The similarity of structural features and control strategies between jointed vertebrate arms and flexible octopus limbs suggests that these configurations evolved separately in octopuses and vertebrates, a result scientists call an example of convergent evolution.

But Greenpeace says in a report released on Tuesday that recent studies estimate that the actual number of such deaths will be 93,000.

Stressing that there is a problem with diagnosis, it adds that other illnesses could take the toll to 200,000.

"Our problem is that there is no accepted methodology to calculate the numbers of people who might have died from such diseases," Greenpeace campaigner Jan van de Putte told Reuters news agency.

"The only methodology that is accepted is for calculating fatal cancers."

But in its report, Greenpeace suggests there will be 270,000 cases of cancer alone attributable to Chernobyl fallout, and that 93,000 of these will probably be fatal.

Blake Lee-Harwood, campaigns director at Greenpeace, told the BBC that cancer was likely to be the cause of less than half of the final fatalities.

"We're also looking at intestinal problems, heart and circulation problems, respiratory problems, endocrine problems, and particularly effects on the immune system," he told the BBC's World Today programme.

The creature, which apparently measured more than 40 feet long, is called Mapusaurus roseae. The discovery of Mapusaurus included bones from at least seven to nine of the beasts, suggesting the previously unknown animal may have lived and hunted in groups. That hunting strategy might have allowed it to attack even bigger beasts, huge plant-eating dinosaurs.

Coria noted the dig showed evidence of social behavior in Mapusaurus. The excavation found hundreds of bones from several Mapusaurus individuals but none from any other creature. That suggests the animals were together before they died, Coria said.

Perhaps they hunted in packs, though there is no direct evidence for that, he said in an e-mail. Currie, in a statement from his university, speculated that pack hunting may have allowed Mapusaurus to prey on the biggest known dinosaur, Argentinosaurus, a 125-foot-long plant-eater.

Holtz called the finding the first substantive evidence of group living by giant two-legged carnivores other than tyrannosaurs. It's not clear whether the animals cooperated in hunting, as wolves or lions do, or simply mobbed their prey or just gathered around after one of them made a kill, he said.

A study by the New Economics Foundation (Nef) and the Open University says 16 April is the day when the nation goes into "ecological debt" this year.

It warns if annual global consumption levels matched the UK's, it would take 3.1 Earths to meet the demand.

But bio-geography professor Philip Stott criticised the "doomsday report", arguing it would hit poorer nations.

"What we tend to have - not just with this report but alternative reports on the other side - are two theological positions," said Prof Stott, of London University.

"This one is the kind of Doomsday report - on the other hand the total free-traders are far too optimistic."

Spirit studied signs of a long-ago explosion at a bright, low plateau called "Home Plate" during February and March. Then one of its six wheels quit working, and Spirit struggled to complete a short advance to a north-facing slope for the winter. "For Spirit, the priority has been to reach a safe winter haven," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the Mars Exploration Rover project.

The rovers have operated more than eight times as long as their originally planned three-month explorations on Mars. Each has driven more than 6.8 kilometers (4.2 miles) about 11 times as far as planned. Combined, they have returned more than 150,000 images. Two years ago, the project had already confirmed that at least one place on Mars had a wet and possibly habitable environment long ago. The scientific findings continue.

Opportunity spent most of the past four months at Erebus, a highly eroded impact crater about 300 meters (1,000 feet) in diameter, where the rover found extensive exposures of thin, rippled layering interpreted as a fingerprint of flowing water. "What we see at Erebus is a thicker interval of wetted sediment than we've seen anywhere else," said Dr. John Grotzinger of the California Institute of Technology, "The same outcrops also have cracks that may have formed from wetting and drying."

In mid-March, Opportunity began a 2-kilometer (1.6-mile) trek from Erebus to Victoria, a crater about 800 meters (half a mile) across, where a thick sequence of sedimentary rocks is exposed. In the past three weeks, Opportunity has already driven more than a fourth of that distance.

Using a high-precision absolute-dating method (techniques involving electron spin resonance and uranium series), Jack Rink, associate professor of geography and earth sciences at McMaster, has determined that Gigantopithecus blackii, the largest primate that ever lived, roamed southeast Asia for nearly a million years before the species died out 100,000 years ago. This was known as the Pleistocene period, by which time humans had already existed for a million years.

"A missing piece of the puzzle has always focused on pin-pointing when Gigantopithecus existed," explains Rink. "This is a primate that co-existed with humans at a time when humans were undergoing a major evolutionary change. Guangxi province in southern China, where the Gigantopithecus fossils were found, is the same region where some believe the modern human race originated."

As the discovery and description of the creature first occurred in the 1920s, it may have had some influence on the core concept of a super large gorilla-like ape that became King Kong, the movie monster, in the 1933 film classic - in fact, a mock documentary about Skull Island on the DVD for the 2005 remake of the film suggests that Kong's species evolved from Gigantopithecus.

A new, unpublished research paper by Kerry Emanuel at the Massachusetts Institute of Technology torpedoes one of the few comforting thoughts of this storm-racked era: The notion that our current spree of active hurricane seasons is part of a natural cycle that's due to calm down in 10 or 20 years.

Instead, Emanuel says, the culprit is probably global warming.

As a result, "it's unlikely we'll ever see a quiet decade for the next 100 years in the Atlantic," said Emanuel, a professor of tropical meteorology and climate, and author of the respected 2005 hurricane text Divine Wind. "I don't think there's any evidence of anything you would call a cycle."

We still could see some calm years here and there, he said — maybe because of a periodic El Niño, which depresses Atlantic hurricanes.

The new paper, co-written with Penn State researcher Michael Mann, promises to stoke a debate Emanuel inspired last summer — when he published research tying global warming to an increase in hurricane strength in both the Atlantic and North Pacific since the 1970s.

What is clear is that over the past century, the world's fish stocks have shrunk. The U.N. Food and Agriculture Organization says that one-quarter of the world's marine stocks are overfished, or harvested faster than the fish can reproduce to replace them, and another half are approaching that point.

Nearly half of the two dozen fisheries managed by the Atlantic States Marine Fisheries Commission are listed as depleted or unknown, including the American lobster, red drum and river herring.

The loss of a stock even temporarily, scientists say, can cost the industry hundreds of millions of dollars and echo throughout the ecosystem, affecting humans, too.

But measuring nature's bounty remains a challenge. Where science leaves a gap, politics rushes in.

In 1992, the collapse of the North Atlantic cod fishery, which devastated Canadian and American fishermen and uprooted entire towns, came about partly because politicians ignored dismal harvest figures in favor of more optimistic forecasts, scientists say.

Mount Everest and the Himalaya mountain range conjure images of yaks and Sherpas loaded with heavy packs. But tucked into the cold shadows of the world's tallest mountain are biologically diverse hotspots filled with poorly known plants and animals found nowhere else on the globe.

Scientists from Conservation International and Disney's Animal Kingdom recently launched a two-month scientific expedition into six regions of the Tibetan "Sacred Lands" in the mountains of Southwest China and Nepal.

"Einstein showed that mass and energy are the same thing," said Mallett, who published his first research on time travel in 2000 in Physics Letters. "The time machine we've designed uses light in the form of circulating lasers to warp or loop time instead of using massive objects."

To determine if time loops exist, Mallett is designing a desktop-sized device that will test his time-warping theory. By arranging mirrors, Mallett can make a circulating light beam which should warp surrounding space. Because some subatomic particles have extremely short lifetimes, Mallett hopes that he will observe these particles to exist for a longer time than expected when placed in the vicinity of the circulating light beam. A longer lifetime means that the particles must have flowed through a time loop into the future.

"Say you have a cup of coffee and a spoon," Mallett explained to PhysOrg.com. "The coffee is empty space, and the spoon is the circulating light beam. When you stir the coffee with the spoon, the coffee - or the empty space - gets twisted. Suppose you drop a sugar cube in the coffee. If empty space were twisting, you'd be able to detect it by observing a subatomic particle moving around in the space."

And according to Einstein, whenever you do something to space, you also affect time. Twisting space causes time to be twisted, meaning you could theoretically walk through time as you walk through space.

"As physicists, our experiments deal with subatomic particles," said Mallett. "How soon humans will be able to time travel depends largely on the success of these experiments, which will take the better part of a decade. And depending on breakthroughs, technology, and funding, I believe that human time travel could happen this century."

These scientists -- working nationwide in research centers in such places as Princeton, N.J., and Boulder, Colo. -- say they are required to clear all media requests with administration officials, something they did not have to do until the summer of 2004. Before then, point climate researchers -- unlike staff members in the Justice or State departments, which have long-standing policies restricting access to reporters -- were relatively free to discuss their findings without strict agency oversight.

"There has been a change in how we're expected to interact with the press," said Pieter Tans, who measures greenhouse gases linked to global warming and has worked at NOAA's Earth System Research Laboratory in Boulder for two decades. He added that although he often "ignores the rules" the administration has instituted, when it comes to his colleagues, "some people feel intimidated -- I see that."

Christopher Milly, a hydrologist at the U.S. Geological Survey, said he had problems twice while drafting news releases on scientific papers describing how climate change would affect the nation's water supply.

Once in 2002, Milly said, Interior officials declined to issue a news release on grounds that it would cause "great problems with the department." In November 2005, they agreed to issue a release on a different climate-related paper, Milly said, but "purged key words from the releases, including 'global warming,' 'warming climate' and 'climate change.' "

Scientists have caught a fossil fish in the act of adapting toward a life on land, a discovery that sheds new light on one of the greatest transformations in the history of animals.

Researchers have long known that fish evolved into the first creatures on land with four legs and backbones more than 365 million years ago, but they’ve had precious little fossil evidence to document how it happened.

The new find of several specimens looks more like a land-dweller than the few other fossil fish known from the transitional period, and researchers speculate that it may have taken brief excursions out of the water.

About 375 million years ago, the creature looked like a cross between a fish and a crocodile. It swam in shallow, gently meandering streams in what was then a subtropical climate, researchers say. A meat-eater, it lived mostly in water.

Yet, its front fins had bones that correspond to a shoulder, upper arm, elbow, forearm and a primitive version of a wrist, Shubin said. From the shoulder to the wrist area, "it basically looks like a scale-covered arm," he said.

"Here's a creature that has a fin that can do push-ups," he said. "This is clearly an animal that is able to support itself on the ground," probably both in very shallow water and for brief excursions on dry land. On land, it apparently moved like a seal, he said.

Characteristic of crayfish is its joined head with the thorax (mid-section) and a segmented body, four pairs of legs and a pair of pincers.

This creature has all those general features but there is something very unusual about the pincers - they are not equally curved claws as in most cases.

Rather, the lower claw is short while the upper claw shapes like a sharp blade three times longer.

And it is combative and fierce.

When Christopher tried to hold it, it lunged forward and snapped its claws with a very audible "dik" like two metal claws hitting each other.