Ancient Tomb Art Found in Path of Irish Highway

Tomb engravings dating back 6,000 years are among the latest discoveries unearthed on the route of a controversial highway under construction in Ireland.

The historic site, at Lismullin in County Meath, was handed over to road builders last month, just weeks after the Stone Age art was found inside a medieval bunker.

The engravings have been removed to allow construction of the highway to proceed.

The new find follows the discovery last spring of a prehistoric open-air temple nearby, causing construction of the 37-mile-long (60-kilometer-long) M3 highway northwest of Dublin to be temporarily suspended (see map).

The timber temple enclosure was found just 1.25 miles (2 kilometers) from the Hill of Tara, once the seat of power of ancient Celtic kings.

The latest excavations at Lismullin revealed part of a huge stone monument, or megalith, decorated with engravings dating to the Late Stone Age, according to archaeologists from Ireland's National Roads Authority (NRA).

Discovered some 165 feet (50 meters) from the temple's enclosure, the stone features a series of zigzags, concentric circles, and arcs.

"It's classic megalithic art," said Mary Deevy, NRA's chief archaeologist.

The engravings are similar to those that decorate other burial chambers in the region known as passage tombs, Deevy noted.

"We've only got half a boulder, but we think originally it was probably a curbstone from a passage tomb," she said.

The stone would have formed a wall that kept the burial mound together, with the artwork displayed on the outer surface, Deevy said.

What the motifs symbolized remains a mystery, the archaeologist added.

Viking Attacks

The stone was discovered within an early medieval souterrain, an underground structure that may have been used by local inhabitants to defend themselves against Viking raiders, the excavation team reported.

Dating to around the 10th century A.D., the souterrain was probably constructed using the broken megalith as building material.

"The souterrain builders robbed or quarried the stone from a Neolithic [Late Stone Age] monument," Deevy said.

"Souterrains are common in Ireland, and it's not unusual to have stones from earlier monuments reused on them," she added.

The rock art will eventually go on public display, according to Deevy, who describes the Lismullin site as "100 percent excavated."

The site was handed over to road builders on December 18, with construction work expected to start soon.

Campaigners who want the highway re-routed away from the Hill of Tara area have attacked the decision.

"Significant damage has already been done," said Vincent Salafia of Dublin-based protest group TaraWatch.

"But until the road is built on top of the site, I suppose there is still hope."

One of the "Top Discoveries"

Irish citizens opposed to the road project are currently fielding legal advice with a view to obtaining a court injunction to halt construction, the campaigner said.

The European Commission has criticized the Irish government for failing to properly reassess the impact of the road project after the ruins of the open-air temple were uncovered last year.

Under European law, the discovery should have triggered a so-called environmental impact assessment, Salafia said.

While the Lismullin site was declared a national monument, "this has made no difference whatsoever," he added.

Upward of 40 archaeological sites have been uncovered along the route of the highway, Salafia said.

"The bigger argument that's at stake is that Lismullin is connected to all these other 40 sites, and that they are all part and parcel of one single large national monument, which is the Hill of Tara complex," he said.

"If a new environment impact assessment were done, that's what would be shown, and that the motorway should go outside that complex rather than straight through it."

Lismullin's timber enclosure site was recently named one of the top ten discoveries of 2007 by the magazine Archaeology, published by the Archaeological Institute of America.

by news.nationalgeographic.com

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Big Dinosaurs Had "Teen Sex"

Big dinosaurs, like humans, reached sexual maturity during the messy growth spurts of adolescence, according to a new study.

The reproductive strategy of dinosaurs was unlike that of their reptilian ancestors or their bird descendants, the study concludes.

"They are growing really fast and yet maturing early," said Sarah Werning, a graduate student in paleontology and integrative biology at the University of California, Berkeley.

"Among living animals, the only things that do that are medium- to large-size mammals, including us."

Though reptiles like crocodiles reach sexual maturity before they are fully grown, they grow slowly. Birds grow to their full adult size within a year but delay sex for a year or longer, Werning noted.

She and colleague Andrew Lee, now at Ohio University in Athens, report the finding in tomorrow's issue of the journal Proceedings of the National Academy of Sciences.

Growth Rings

Like tree trunks, dinosaur bones have annual growth rings, Werning said.

The researchers were studying these rings in the bones of the meat-eater Allosaurus and the plant eater Tenontosaurus to determine how fast they grew at different points in their lives.

In a specimen of each type of dinosaur, the team happened upon a type of calcium-rich tissue called medullary bone. Modern-day birds also produce this type of bone prior to laying eggs.

The finding indicates that both the Allosaurus and the Tenontosaurus died shortly before laying eggs—and therefore that they were able to reproduce at the times of their deaths.

"They wouldn't be ovulating if they weren't of reproductive age," Werning noted.

The researchers added this onset of sexual maturity to their growth graphs and found that the dinosaurs were reaching sexual maturity in the midst of a teenage growth spurt.

"They are definitely not juveniles, but they are not fully grown yet, and they are also going through a time of really rapid growth … it's very similar to what we call adolescence," Werning said.

The team also confirmed that a Tyrannosaurus rex bone that North Carolina State University paleontologist Mary Schweitzer found in 2005 contained medullary tissue when it died at 18.

(Related: He Rex or She Rex? Experts Find Way to Tell Dino Gender [June 2, 2005].)

All three types of dinosaurs had life spans of about 25 to 30 years. But they didn't reach full adult size until age 20 to 25. Waiting until they were fully grown to reproduce would have been risky, according to Werning.

"It makes a lot of sense that [dinosaurs] wouldn't have the same strategy as birds," she said.

Birds Are Unique

The finding complements research published last year that showed that birdlike dinosaurs—discovered sitting on their eggs just like birds do—also had sex as teenagers.

"What Sarah and Andrew have done in their paper is find exactly the same thing but in a different group of dinosaurs and by using a different marker of reproductive maturity," said Kristi Curry Rogers, a paleontologist at Macalester College in St. Paul, Minnesota.

Curry Rogers is a co-author of the 2007 birdlike-dino study with Gregory Erickson, a paleontologist at Florida State University.

She said both studies highlight the uniqueness of sexual maturity in birds.

"[Bird] evolution is a very fascinating mosaic of characteristics that deserves a lot more study," she said. "We're still at the beginning of teasing apart all the fine details."

by news.nationalgeographic.com

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Mysterious Clouds More Common Due to Climate Change?

Mysterious "night-shining clouds" that light up the polar skies have become more luminous and frequent in recent years—and climate change may be the culprit, scientists announced Monday.

So-called noctilucent clouds, which streak across the sky in vibrant colors during polar summers, are ten times brighter than previously believed, according to recent data from NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite.

The data, collected during two polar cloud seasons, also suggest the formations appear daily, are more widespread, and have started to form at lower latitudes than before.

Climate Change Canary

Night-shining clouds are made mostly of ice particles that form when water vapor condenses onto atmospheric dust.

The AIM mission is the first detailed exploration of the clouds, which form about 50 miles (80 kilometers) above Earth's surface—"literally on the edge of space," AIM principal investigator James Russell III said yesterday at a press briefing at the American Geophysical Union fall meeting in San Francisco, California.

The air there is a thousand times drier than the Sahara, and the temperature can drop to minus 235 degrees Fahrenheit (minus 148 degrees Celsius)—ideal conditions for creating clouds.

A likely explanation for the clouds' surge is that temperatures in the upper atmosphere have gotten even colder due to the build-up of carbon dioxide in the atmosphere, Russell said.

Yearly emissions of carbon dioxide levels have grown about 20 percent since 1990. Most scientists agree the buildup is causing climate change and heating up Earth's surface.

In the upper atmosphere, however, carbon dioxide does not act like a thick, heat-trapping blanket.

Instead it forms a thin layer, allowing heat to escape, temperatures to drop, and ice particles to form.

"[These] clouds are the mine's canary of global warming," Russell told National Geographic News.

No Other Plausible Reason

The evidence linking carbon dioxide to changes in night-shining clouds is still tentative, Russell said.

But "in all honesty, we don't know of any other plausible reasons why it wouldn't be global climate change," he said.

"If that's true, that says not only are we changing the atmosphere where we're living, we're changing a very remote, rarified part of our atmosphere."

Such far-reaching change means that "we need to be concerned," Russell said.

"If [the cloud changes] are indeed tied to carbon dioxide buildup, here's another confirming reason we should strive to do something about it."

"Exquisite Thermometer"

AIM also discovered "dramatic changes" in cloud behavior, said Scott Bailey, AIM's deputy principal investigator.

The data suggest the clouds are highly variable, rotating every five days according to minute shifts in temperature—even as little as 5 degrees Fahrenheit (2.7 degrees Celsius).

"These clouds are exquisite thermometers," he said.

"Now we're able to see the whole life cycle [of a cloud] for the first time," Bailey told National Geographic News.

by news.nationalgeographic.com

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