Scientists are now convinced that Arctic sea ice is showing signs of both a winter and a summer decline that could indicate a major acceleration in its long-term rate of disappearance. The greatest fear is that an environmental "positive feedback" has kicked in, where global warming melts ice which in itself causes the seas to warm still further as more sunlight is absorbed by a dark ocean rather than being reflected by white ice.

Mark Serreze, a sea ice specialist at the US National Snow and Ice Data Centre in Colorado, said: "In September 2005, the Arctic sea ice cover was at its lowest extent since satellite monitoring began in 1979, and probably the lowest in the past 100 years. While we can't be certain, it looks like 2006 will be more of the same," Dr Serreze said.

"Unless conditions turn colder, we may be headed for another year of big sea ice losses, rivalling or perhaps even exceeding what we saw in September 2005. We are of course monitoring the situation closely ... Coupled with recent findings from Nasa that the Greenland ice sheet may be near a tipping point, it's pretty clear that the Arctic is starting to respond to global warming," he added.

Although sea levels are not affected by melting sea ice - which floats on the ocean - the Arctic ice cover is thought to be a key moderator of the northern hemisphere's climate. It helps to stabilise the massive land glaciers and ice sheets of Greenland which have the capacity to raise sea levels dramatically.

Dr Serreze said that some parts of the northern hemisphere experienced very low temperatures this winter, but the Arctic was much warmer than normal. "Even in January, when there were actually record low temperatures in Alaska and parts of Russia, it was still very warm over the Arctic Ocean," he said.

"The sea ice cover waxes and wanes with the seasons. It partly melts in spring and summer, then grows back in autumn and winter. It has not recovered well this past winter - ice extent for every month since September 2005 has been far below average. And it's been so warm in the Arctic that the ice that has grown this winter is probably rather thin," he explained.

Professor Peter Wadhams, of Cambridge University, who was the first Briton to monitor Arctic sea ice from nuclear submarines, said: "One of the big changes this winter is that a large area of the Barents Sea has remained ice-free for the first time. This is part of Europe's 'back yard'. Climate models did predict a retreat of sea ice in the Barents Sea but not for a few decades yet, so it is a sign that the changes that were predicted are indeed happening, but much faster than predicted."

And just like the butterfly whose single flapping of a wing on one side of the world might help precipitate a tornado on the other side, a single leaf can have large consequences for the weather.

"How well we are able to represent one leaf in a weather forecast model can be a key to predicting thunderstorms," said Dev Niyogi, an assistant professor of agronomy and earth and atmospheric sciences at Purdue University. "The amount of moisture plants are emitting during photosynthesis may be considered the local trigger that trips fronts into violent weather."

Researchers in plant biology have long used models of photosynthesis to look at environmental changes. Photosynthesis is the process by which plants convert carbon dioxide and water into carbohydrates using solar energy. But
weather simulators have never directly incorporated photosynthesis models for forecasting weather.

"We coupled a photosynthesis-based vegetation model to a weather forecast model and tested the improvement one could obtain by this for simulating severe weather situations," Niyogi told LiveScience.

This, combined with improved mapping of soil moisture, allows for better predictions of specific, local events.

"Our results showed that, while the current weather forecast and vegetation models do a fair job in simulating the weather, the results in terms of timing, location and intensity of local-scale thunderstorms can be improved by adopting more detailed photosynthesis transpiration models," Niyogi explained.

These improvements can improve forecasting of factors such as temperature and humidity anywhere from 5 to 50 percent.

"It certainly makes us think, what other factors may be important that we should be considering and how that may improve matters further," Niyogi said.

On Monday, a second line of storms raked the region, with rain, hail and fierce wind tearing up trees and homes from Kansas through Indiana.

The weekend storms left four people dead in Renick, a rural community about 30 miles north of Columbia, Missouri. The death toll also included a married couple killed when a twister hurled their pickup truck beneath a propane tank about 80 miles south of St. Louis.

Missouri Gov. Matt Blunt declared a state of emergency throughout Missouri, Illinois Gov. Rod Blagojevich declared a disaster in seven counties, and three southern Indiana counties were under states of emergency.

Classes at the University of Kansas in Lawrence were canceled Monday because of the danger of falling debris. University Chancellor Robert Hemenway put the damage at $6 million. Classes were to be held as scheduled Tuesday, though one building was to remained closed and access restricted to three others.

Illinois' capital was hit hard twice in 24 hours, first by a tornado and then strong wind early Monday that blew debris through the city. Power lines were down across Springfield, trees uprooted and windows blown out.

Mayor Tim Davlin said he expected "every square inch of Springfield'' will have suffered some effect from the storms.

"It's just unreal,'' Davlin told The (Springfield) State Journal Register early Monday from the city's Emergency Operations Center.

Most major roads into the city were closed, and one man was reported missing after his home was destroyed. The roof was torn off a Wal-Mart store, and police were searching damaged homes and businesses Monday for people who could be trapped, said city spokesman Ernie Slottag. At least 19 people were treated for minor injuries.

Most of Springfield was without power, and thousands of homes outside the city were blacked out elsewhere in Illinois.

The tornado that struck Springfield on Sunday had made a two-hour pass through central Illinois.

The Scott County, Ill., sheriff's department confirmed that a tornado touched down in Manchester, a town of about 300 people, although there were no immediate reports of injuries.

"It's a mess over there,'' Scott County sheriff's department dispatcher Rosann Lindsey said of Manchester. "A lot of buildings are down over there.''

The Chicago area also was struck by high wind, with gusts to 70 mph in suburban Tinley Park, and roofs were blown off apartment buildings in suburban Bridgeview. Localized flooding was reported in the Chicago and Quad Cities areas.

Missouri was hardest hit by the weekend storms, with at least nine people killed and hundreds of homes and businesses destroyed or damaged. Hail as big as softballs pounded parts of the state.

Bobby Ritcheson, 23, said he watched as a neighbor was killed south of Sedalia, Mo.

"The trailer came down right on top of her,'' Ritcheson said.

Homes were destroyed along a path of more than 20 miles south of St. Louis, officials said.

The vast weather system arose as moist air from the Gulf of Mexico collided with cold Canadian air, said Philip Schumacher of the National Weather Service in Sioux Falls, S.D. The system dumped 20 inches of snow in parts of western South Dakota and knocked out power and closed schools as it moved into Minnesota and Wisconsin.

"It is a sign that spring is coming,'' said Schumacher. "You start getting stronger low-pressure systems, and they're able to bring in stronger south winds, which tend to bring up more moisture.''

At the University of Kansas, where 60 percent of the buildings were damaged by weekend storms, Provost David Shulenberger said classes were canceled Monday because of safety concerns about debris falling from roofs. The Lawrence campus was littered with trees, roof tiles and window glass.

Two trees fell through Rhonda Burns' mobile home in Lawrence early Sunday.

"If the wind had shifted that tree just a few inches, I wouldn't be talking to you,'' she said.

Tornadoes also destroyed dozens of homes Sunday in Oklahoma and Arkansas.

"It was over before you knew it,'' said Greg Kospar, 41, of Bentonville, Ark. "The house is gone.''

Missouri authorities reported nine people killed, including four whose bodies were found in the rubble of homes near the town of Renick.

Another storm victim was found in Indiana, where several people had to be rescued from cars stalled in rapidly rising water. Flood warnings were posted Monday for large areas of southern and central Indiana.

The incident closed a half-mile stretch of Farrington Highway between Haleakala Avenue and Lualualei Naval Road, cutting off access to the Wai'anae Coast until the Army opened Kolekole Pass to civilian traffic about 2 p.m. That bypass was to remain open until at least through today's morning rush hour, officials said.

Police said crews were also trying to open two town-bound lanes of Farrington Highway by this morning, but could not say exactly when that would happen. One cause for worry, police said, is that some poles left standing may have been weakened.

Police said 20 vehicles were damaged. Laurie Grace, emergency medical services supervisor for Nanakuli, said EMS did not take anyone to the hospital.

A pole flattened the roof of a Chevy Astro van down to the window sills, but the three people inside escaped with only a scrape to the shoulder of driver Dexter Li'i.

"The first thing I did was yell, 'Are you two OK?' " Li'i said of his passengers, La Aukai and Daryl Ching. "And they both said yeah. My door was already open and I got out and told everyone around me, 'I got two passengers in here' and right away a whole lot of people came and helped get them out."

Aukai, who was sitting in a back seat, said she saw the pole falling "and I screamed, 'It's coming!' "

Pointing to the occupants of the Astro, Grace said, "These guys have angels watching over them."

The poles carried power lines of 12,000 volts and 46,000 volts, Hawaiian Electric Co. spokesman Ben Obayashi said.

Police Lt. Farrell Sojot said police were concerned about keeping people away from the power lines because some wires were sparking.

"Initially the lines were still hot, so we couldn't even get to the people inside (the cars)," Wai'anae watch commander Lt. Frank Pugliese said. "We told everybody to stay in place. But then HECO cut the power."

Fire battalion chief Eric Adams said: "It's like a hurricane hit. It's amazing there are no injuries and with all the power lines down nobody got shocked. Two cars are crushed."

National Weather Service lead forecaster Roy Matsuda said radar spotted 45 mph trade winds coming from the east between 12:30 and 1 p.m., about one mile in altitude.

"When a 45 mph wind dips down from aloft, it can accelerate to higher speeds," Matsuda said. "It is freakish, out of the norm."

HECO spokeswoman Sharon Higa said, "It is a rare and unusual circumstance. Poles are designed to withstand 80 mph winds, which is near hurricane-type conditions. It's hard to say what factors caused the poles to fall. It is under investigation."

About 700 HECO customers lost power at the outset; about 225 customers remained without power at 8 last night, Higa said.

HECO had 36 repair workers at the scene last night, Higa said.

Adams said one severed pole looked like it had termite damage.

Rodney Amalza, 22, of Mililani, was driving home from Wai'anae in a Ford Expedition SUV with his 14-month-old daughter when the wind came up and knocked down a pole.

"After that, it was just like dominos," Amalza said. "Everything was going down; it was real fast. The second pole I saw go down landed on the roof of the car in front of me. The wires were coming down, the bucket on the poles and all the stuff were hitting cars.

"About five power lines landed on my car; there were two on the hood and some on the passenger-side mirror. It was spooky because I saw sparking."

He and his daughter stayed in the vehicle until he was told HECO had turned off the power.

Police said a fallen pole damaged a house at 87-2130 Farrington Highway. As the pole snapped, the broken end kicked back and hit the house, cracking a wooden wall.

Three witnesses told police that a "twister" came through from the mountains, Sojot said. "One witness said a tree got blown down and then the pole started coming down on Nanaikeola Street. There was a domino effect from there."

But EMS supervisor Grace said she saw the poles come down and "it wasn't a domino effect. They just all came down at once - whump!"

"It was crazy," said Darlene Aweau, who had been sitting in her Nissan pickup parked on the makai side of Farrington Highway. "The wind was shaking the truck and sand was just flying through the window. And the pole snapping made the biggest noise, like a tree breaking."

Of the 20 vehicles involved, three suffered major damage, police said.

Nanakuli resident Manu Afong said he saw blue flames shoot from electrical boxes after the poles crashed to the ground. Traffic was immediately gridlocked, he said.

"There's no way in or out," Afong said.

Large vehicles such as buses were not able to use the steep, winding Kolekole Pass emergency route. Oahu Transit Services bus route No. 40 to the Wai'anae Coast was taking riders in as far as it could on Farrington Highway. Passengers were then walking a ways to shuttle buses running on the Wai'anae side.

Kaiser Permanente's Nanaikeola Clinic at 87-2116 Farrington Highway will be closed today, spokeswoman Lynn Kenton said. Staff should report to the Waipio Clinic at 94-1480 Moaniani St. Patients may call 432-3500.

Nanakuli resident Fale Esekia was driving home from church with her mother when the poles fell, stranding them at Nanakuli Shopping Center. "This is worse than Hurricane Iniki," she said. "Wai'anae got hit hard by that storm, but it was nothing like this.

"It's a miracle that no one got killed."

Reach Will Hoover at whoover@honoluluadvertiser.com and Rod Ohira at rohira@honoluluadvertiser.com.

On Tuesday, firefighters were bracing for the possibility of a shift in wind direction and dropping humidity as they worked to strengthen the perimeters around the blazes, said Jan Fulkerson, a spokeswoman for the Texas Forest Service. The wind was near 20 mph mid-morning and there was no rain in sight.

The Department of Public Safety late Monday attributed four new deaths to the fires, bringing the death toll to 11. Nine firefighters have been injured.

"We share in the grief of those who have lost family members and loved ones, and we offer our prayers," Gov. Rick Perry said. "Throughout this wildfire season, communities in our state have shown strength and resolve that are uniquely Texan."

Eleven fires were burning across an estimated nearly 700,000 acres Monday, up from 663,000 over the weekend. State fire crews fought more than 160 blazes in one 24-hour period.

The size of the blackened area easily eclipsed the 455,000 acres that burned in December and January, when the governor declared a disaster.

Fire evacuee Jennifer Orand returned Monday to find her mobile home in the Hutchinson County community of Texroy burned to the ground.

"I just started crying," said Orand, 27, who lives with her husband, Shannon, about 40 miles northeast of Amarillo. "You hear all the time that people think it will never happen to you. I never thought I'd say that myself."

A series of rural fires stretching through Collinsworth, Wheeler, Carson, Hutchinson, Donley and Gray counties, charred some 652,000 acres by Monday night, and were still burning early Tuesday, the Texas Forest Service reported.

Another wildfire in Childress and Cottle counties reached 45,000 acres, the Texas Forest Service said.

In southeastern New Mexico, authorities contained a 92,000-acre fire that had charred tinder-dry brush, burned the McDonald post office and two homes, and forced about 200 people to evacuate. It appeared to have been started by an emergency flare at a natural gas plant, Lovington fire officials said.

Texas Department of Public Safety reported seven firefighters suffered minor injuries fighting the blazes in the Panhandle. One was hospitalized in stable condition Monday night after a wreck in his fire truck. A ranch hand assisting firefighters was hospitalized with second-degree burns.

About 3.5 million acres _ 2 percent of Texas land mass _ has burned since Dec. 26, said Rachael Novier, a spokeswoman for Perry.

"There's no way you can protect the United States by building a big cage around it and preventing wild birds from flying in and out," U.S. Secretary of Agriculture Michael Johanns said.

U.S. spy satellites are tracking the infected flocks, which started in Asia and are now heading north to Siberia and Alaska, where they will soon mingle with flocks from the North American flyways.

"What we're watching in real time is evolution," said Laurie Garrett, a senior fellow for global health at the Council on Foreign Relations. "And it's a biological process, and it is, by definition, unpredictable."

Industry Precautions

America's poultry farms could become ground zero as infected flocks fly over. The industry says it is prepared for quick action.

"All the birds involved in it would be destroyed, and the area would be isolated and quarantined," said Richard Lobb of the National Chicken Council. "It would very much [look] like a sort of military operation if it came to that."

Extraordinary precautions are already being taken at the huge chicken farms in Lancaster County, Pa., the site of the last great outbreak of a similar bird flu 20 years ago.

Other than the farmers, everyone there has to dress as if it were a visit to a hospital operating room.

"Back in 1983-1984, we had to kill 17 million birds at a cost of $60 million," said Dr. Sherrill Davison, a veterinary medicine expert at the University of Pennsylvania.

Can It Be Stopped?

Even on a model farm, ABC News saw a pond just outside the protected barns attracting wild geese.

It is the droppings of infected waterfowl that carry the virus.

The bird flu virus, to date, is still not easily transmitted to humans. There have been lots of dead birds on three continents, but so far fewer than 100 reported human deaths.

But should that change, the spread could be rapid.

ABC News has obtained a mathematical projection prepared by federal scientists based on an initial outbreak on an East Coast chicken farm in which humans are infected. Within three months, with no vaccine, almost half of the country would have the flu.

That, of course, is a worst-case scenario - one that Lobb says the poultry industry is determined to prevent with an aggressive strategy to contain and destroy infected flocks and deny the virus the opportunity to mutate to a more dangerous form but one that experts say cannot be completely discounted.

The current bird flu strain has been around for at least 10 years and has taken surprising twists and turns - not the least of which is that it's now showing up in cats in Europe, where officials are advising owners to bring their cats inside. It's advice that might soon have to be considered here.

After two decades, the legacy of the Chernobyl disaster is still casting its poisonous shadow over Britain's countryside. The Department of Health has admitted that more than 200,000 sheep are grazing on land contaminated by fallout from the explosion at the Ukrainian nuclear plant 1,500 miles away. Emergency orders still apply to 355 Welsh farms, 11 in Scotland and nine in England as a result of the catastrophe in April 1986.

The revelation - in a Commons written answer to the Labour MP Gordon Prentice - comes as Mr Blair prepares to make the case for nuclear power in a forthcoming government Energy Review. The Prime Minister argues that nuclear energy would allow the UK to achieve twin objectives of cutting C02 emissions and reducing dependency on imported natural gas supplies.

But, just last week a damning report from the Government's own advisory board on sustainable development identified five major disadvantages to any planned renewal of Britain's nuclear power programme, including the threat of terrorist attack and the danger of radiation exposure. The longevity of the "Chernobyl effect" in a region generation of nuclear power stations, and going through a consultation exercise to try to convince the public that this is a safe form of electricity generation, we shouldn't overlook the terrible consequences if something does go wrong,

"No one would now build a reactor as unsafe as those at Chernobyl, which were jerry built. Even so, I think a lot of people will be shocked to know that, as we approach the 20th anniversary of Chernobyl, hundreds of farming families are still living with the fallout."

Jean McSorley, Greenpeace's senior adviser on nuclear energy said: "Chernobyl was the worst nuclear accident the world has ever seen but it is by no means the worst that could happen. In Cumbria, where I come from, people who are old enough to remember still talk about it. It's quite moving to hear the stress that farming families were put through. I think the British public that all this distance from Chernobyl, 20 years later, so many families are still living with its impact day to day."

The Chernobyl disaster turned public opinion in Britain against civil nuclear power overnight. The land still poisoned by Chernobyl's radioactivity lies all along the Welsh hills between Bangor and Bala, much of it in the Snowdonia National park. There is also a large triangle of contaminated land in Cumbria, south of Buttermere - though the number of farms affected is smaller than in Wales.

Some of the Scottish hills are also still affected. No sheep can be moved out of any of these areas without a special licence, under Emergency Orders imposed in 1986. Sheep that have higher than the permitted level of radiation have to be marked with a special dye that does not wash off in the rain, and have to spend months grazing on uncontaminated grass before they are passed as fit to go into the food chain.

A National Farmers' Union spokesman said: "The paramount concern has to be the safety of the consumer, and consumer confidence in the meat supply, so exceptional care has to be taken to make sure no contaminated meat goes into the food chain."

Most of Britain's nuclear power stations have either ceased to produce electricity, or are nearing the end of their active life. The last is due for closure in 2035. The Government is now conducting an energy review, to be published in June, which is expected to announce a new nuclear programme.

Tony Blair signalled his support for the industry in a speech to Labour's conference last autumn, when he warned Britain is too reliant on "unstable" regimes for its energy supplies, and singled out nuclear power as an alternative.

But resistance to the idea has been growing, particularly with the publication last week of the report by the government's Sustainable Development Commission. The Commons Environmental Audit Committee will also report later this month. According to a committee member, their findings are expected to be "measured" but "certainly won't put a strong case for nuclear power".

On 23 March, leading specialists will hold a conference in London on the long term impact of Chernobyl. At the end of the month, the Nuclear Decommissioning Authority will issue a revised figure for the cost of cleaning up the sites of disused publicly owned nuclear plants.

Their figure is expected to be substantially higher than their original estimate which was published last year, of £56bn.

David Ellwood, 49, farmer: 'Nobody can tell us when the radiation will pass'

By Geneviéve Roberts

David Ellwood has 700 sheep on his farm in Ulpha, near Broughton-in-Furness. His wife, Heather, 50, helps out on Baskell Farm, and they have four children.

"I remember the Chernobyl disaster 20 years ago. We were lambing in April and it was raining like hell. We got a letter from the ministry suggesting it would last about three weeks, but they were only guessing - it could go on for another 20 years.

"Every time we take sheep to auction, we must phone Defra, who check they are clear from contamination [from radioactive caesium]. They give us £1.30 for every sheep they monitor. We take them off the fell and put them in the fields for a couple of weeks before selling them, so readings are usually low. But the odd one gets a high reading if it comes straight in off the fell, and has to be slaughtered.

"Defra are here four or five times a year which is a hassle. At shearing time in July they monitor everything. If we are taking Cheviots to auction, we have to get them into a pen to take readings, which makes them mucky and bad for selling. Now we try to get them monitored three or four days before," said Mr Ellwood, 49. "We have been on this farm for 16 years, and owned the ground surrounding it before that, so have always been affected by Chernobyl. There is a lot of contaminated peat on our fell, so when the grass comes up in the summer that gets contaminated too. If our fell were rocky, I don't think it would be such a problem.

"I could get angry, but it is pointless, there is not a damn thing we can do and nobody seems to know when it will pass. I would be worried if more power stations were built. We were 1,500 miles from Chernobyl and still feel the effects."

Edwin Noble, 45, sheep farmer: 'I had no idea it could affect us so far away'

Edwin Noble and his family, who run a 2,500- acre farm close to Mount Snowden, live under emergency restrictions that they were told would apply for 30 days, but which are likely to continue for years.

Mr Noble, 45, was in his early twenties when he took charge of the family farm. On the night of 2 May 1986, he was disturbed by torrential rain and feared the river would burst its banks. What he did not know was that the radiation cloud from Chernobyl was passing invisibly overhead. The rain left huge deposits of radioceasium in the peaty soil, which is no direct threat to humans but works itself into the grass, contaminating his sheep.

"I had heard about Chernobyl on the news, but had no idea at all that [it] could affect us so far away," he said. "It's something we have had to live with ever since.

"Every time we move a sheep or lamb off our land it has got to be scanned. If it fails the monitoring, it ... cannot be sold. If you can get the sheep or lamb off the contaminated land, then the radiation comes out of them fairly quickly, but the whole of our farm is affected, so we rent grazing land 20 miles away. It means you constantly have to think ahead. If the lamb is fattened and ready to go to market, you can't have it sitting in a pen waiting to be monitored because it loses weight, so you've got to get the monitoring done ahead of time. When the market is volatile, it has cost us a sale.

"The experience has made me very opposed to nuclear power. It's not so much the inconvenience for farmers like us - but what if the explosion had been at the plant near here, at Trawfynydd? It doesn't seem worth the risk," he said.

The leak, whose cause is unknown, occurred in a remote part of the most sparsely populated state in the United States, and it remains to be seen what damage, if any, it has done to ecosystems. It does, however, give grist to groups who have challenged Washington's assertion that oil can be prospected and shipped while leaving only the gentlest of "footprints" on the landscape.

"This historic oil spill is a catastrophe for the environment," Natalie Brandon, of the Alaska Wilderness League, said in a statement. "Tone-deaf politicians in Congress should now stop trying to push for more drilling through sneaky manoeuvres ... The fact that the oil spill occurred in a caribou crossing area in Prudhoe Bay is a painful reminder of the reality of unchecked oil and gas development across Alaska's North Slope."

The biggest battle has been over the fate of the Arctic National Wildlife Refuge, also on the North Slope, which the White House wants to open up. The initiative, championed from the moment the Bush administration took office in 2001, has been consistently blocked by Congress but is periodically revived.

A second battle, meanwhile, is taking place in a previously untouched corner of the National Petroleum Reserve on the North Slope. The Bush administration has allowed oil companies to prospect for oil and gas in an area covering 389,000 acres. Environmental groups have responded with a federal lawsuit, filed last Friday, in which they contend that the Department of the Interior has violated the Endangered Species Act and other laws in an area noted for its flocks of migratory geese.

It is not just environmentalists who oppose the administration's plans. Several prominent energy analysts, as well as Washington politicians, argue that the likely yield in unexplored areas of the North Slope is not large enough to justify the intrusion.

Alaskan politicians and industry lobby groups are heavily in favour of expanding exploration as it would bring jobs and other benefits to the state economy. The Bush administration, meanwhile, argues that further domestic exploration is essential if the United States wants to decrease its dependence on oil and gas from the Middle East.

Accidents and leaks have periodically occurred on the North Slope, and along the trans-Alaska pipeline that takes crude from Prudhoe Bay across two mountain ranges to the port of Valdez on the shores of the North Pacific. Saboteurs blew up a section of pipeline shortly after it opened in the 1970s, starting a major spillage. A hunter accidentally fired into the pipeline five years ago, causing $7m (£3.6m) worth of damage.

A study published in a recent issue of the Public Library of Science's genetics journal, suggests that, as a result, today's creative dancers actually share two specific genes. Both genes are associated with a predisposition for being good social communicators.

Scientists believe this gave early humans who were well coordinated and rhythmic a distinct evolutionary advantage.

Dancing genes

"Dance, like music, is an activity dating to prehistoric times that is sometimes a sacred ritual, sometimes a form of communication, and sometimes an important social and courtship activity," wrote the researchers, who were psychologists based primarily out of universities in Jerusalem. "We hypothesized that there are differences among individuals in aptitude, propensity, and need for dancing that may partially be based on differences in common [genes]."

DNA was obtained from 85 elite dancers and their parents to compare with a group of people lacking any distinguishing characteristics, as well as a group of athletes. The genes studied don't control a specific physical ability, but they dictate two well-known social and behavioral chemicals in the body: serotonin and vasopressin.

As researchers suspected, both chemicals were found in much larger quantities among the dancers. In other words, while the elite dancers couldn't be put in a different physical category from everyone else, they all shared genes that made them more social.

The survival dance

This innate ability was crucial in prehistoric times, according to Steven J. Mithen, and archaeologist at the University of Reading in the United Kingdom.
"Cooperation would have been essential for survival during the last Ice Age and this would have been facilitated by the social bonds that develop through communal dancing and singing," Mithen told LiveScience.

In his new book "The Singing Neanderthals: The Origins of Music, Language, Mind, and Body" (Harvard University Press, 2006), Mithen contends that because of their communication powers, dance and music likely became an important tool of social interaction as soon as humans could walk and talk.

"It has been argued that the specific nature of human anatomy suggests that it evolved for endurance running as much as walking. As such it could have also been used for dancing, as bipedalism requires high degrees of muscle control, balance and flexibility," he said.

Dance like a Neanderthal

Mithen's research focuses on the Neanderthals-our prehistoric cousins-as opposed to Homo sapiens' direct ancestors. But he believes the importance of dance was widespread and probably practiced by early humans, too, as far back as 1.5 million years ago.

And, as it is on modern dance floors, their prehistoric moves had a lot to do with hooking up.

"In many societies today dancing is used as a form of display for attracting mate," Mithen points out. "Dancing is a means to show off one's physical fitness and co-ordination, qualities that would have been useful for survival in prehistoric hunter-gatherer societies."