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A GREAT LEAP BACKWARDS
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| Author:
The Economist, USA
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Date:
01/01/2001
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| Abstract |
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| Geologists have found evidence for the existence of a new
supercontinent
MANY organisations use a map of the world as their logo. So does
the journal GONDWANA RESEARCH--but its logo consists of a
bunch of unfamiliar blobs snugly cuddled against each other. This
image represents the earth as it is thought to have looked 200m years
ago, when all the continents were clustered together in a
"supercontinent" known as Pangaea. Gondwanaland was the name
given to the southern half of this landmass, the part that includes
modern-day Africa, Australia, South America, Antarctica and India.
In the latest issue of the journal, a pair of geologists present their idea
of what the planet might have looked like long before Pangaea and
Gondwanaland had formed.
According to John Rogers, who works at the University of North
Carolina in Chapel Hill, and Santosh, an Indian geologist at Kochi
University in Japan, geological evidence suggests that, a billion and a
half years earlier, another supercontinent existed. They have dubbed
this continent "Columbia", because some of the best evidence for its
existence comes from the Columbia river region of the north-western
United States. |
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New Fossils Support Deep-Sea Origin of Life
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| Author:
Fox News
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Date:
07/08/2007
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| Abstract |
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| FOXNEWS.COM HOME > SCIENCE
New Fossils Support Deep-Sea Origin-of-Life Theory
Friday, August 03, 2007
By Dave Mosher
Geologists have discovered 1.43 billion-year-old fossils of deep-sea microbes, providing more evidence that life may have originated on the bottom of the ocean.
The ancient black smoker chimneys, which scientists unearthed in a Chinese mine, are 1 billion years older than similar fossils previously identified and are nearly identical to the archaea- and bacteria-harboring structures found today on sea beds.
"These are remnants of the oldest living types of life forms on the planet," said Timothy Kusky, a geologist at Saint Louis University and co-author of a new study that describes the fossils.
Kusky said that the fossils offer "tantalizing suggestions" that life developed near deep-sea hydrothermal vents and not in shallow seas, as other evidence hints.
A crosscut of one of the 1.43 billion-year-old black smoker fossils recovered from an exploratory mine in northern China.
Black smoker chimneys develop at submerged openings in the Earth's crust that spew out mineral-rich water as hot as 752 degrees Fahrenheit (400 degrees Celsius).
Bacteria that don't depend on sunlight or oxygen move into the fragile chimneys that grow around the vents and feed on the dissolved minerals.
"Some people like to call it life in extreme environments. These bacteria pretty much live on a different planet compared to conditions we live in," Kusky told LiveScience.
The stony chimneys can grow more 50 feet (15 meters) tall, but retrieving even a modern chimney sample is extremely difficult, as they're fragile and can crumble when touched.
"This discovery offers scientists valuable on-land samples for geological and geo-biological research," Kusky said, noting that some of the fossils he unearthed measure a whopping 3 feet in length.
The age and size of the chimneys, Kusky said, will help scientists understand how ancient hydrothermal vent growth and the development of life on the sea floor might be interconnected.
Although the fossils may be old, they aren't the oldest evidence of life on Earth.
The most ancient specimens are 3.5 billion-year-old, dome-shaped clumps of bacteria called stromatolites, which were found in western Australia and suggest that shallow seas were the birthplace of life.
Ed Mathez, a geologist and curator at the American Museum of Natural History in New York who is not connected to the discovery, said even with the evidence of stromatolites, the verdict on life's origin is out.
"They tell us life existed that long ago, but as to where it originated remains an open question," Mathez said. Mathez pointed out that black smoker fossils are just as inconclusive about the origin of life , but added that the new finding significantly pushes back the known reign of deep-sea microbes.
"Personally, a deep-sea origin of life strikes me as a very good possibility," he said.
In the end, Kusky said, there may yet be even older black smoker chimney fossils waiting to be discovered. "So far, these fossils provide oldest evidence for deep-sea life," he said.
His team's findings are detailed in the current issue of the journal Gondwana Research.
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Ancient Crayfish Fossils Unravel Evolution Mystery
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| Author:
National Geographic News
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Date:
03/04/2008
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| Abstract |
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| Scott Norris
for National Geographic News
February 8, 2008
New fossils of ancient crayfish and their branching burrows provide the oldest evidence of crayfish in the Southern Hemisphere, experts say. The discovery in Australia of a 106-million-year-old crayfish fossil—and even older "trace fossils" of the animal's streamside burrows—help fill in a puzzling gap in the history of the small crustaceans.The finding supports a theory that the evolution of crayfish has been strongly shaped by the drift of Earth's continents, researchers say. Crayfish are the freshwater cousins of marine lobsters. Hundreds of known species are divided into two distinct groups, one in the Northern Hemisphere and the other in the Southern Hemisphere. "It's been a mystery how and when they split into these groups," said Anthony Martin of Emory University in Atlanta, Georgia, who led the fossil discovery team. Contributing to the mystery was an absence of any very old crayfish fossils from the Southern Hemisphere. Fossils have shown that crayfish were present in the Northern Hemisphere at least 150 million years ago. But for over a century biologists have been puzzled by the lack of any comparably old fossils from the southern continents. "There was a 60- to 70-million-year gap in the fossil record," Martin said. "Now we're a lot closer to the origin point of the Southern Hemisphere crayfish." The study by Martin's team is set to appear in a forthcoming edition of the journal Gondwana Research.Evolution and Continental DriftScientists have long debated whether today's northern and southern crayfish all descend from a common ancestor that was already adapted to fresh water, or if the two groups evolved the freshwater adaptation independently of one another. A shared freshwater ancestor would require that crayfish first evolved very early, when all of Earth's continents were united in a single landmass called Pangaea. This theory has been supported by genetic studies that suggest the two crayfish groups diverged around the same time that Pangaea split into northern and southern "supercontinents" about 185 million years ago. (See a map of Earth's moving plates.)Ancestors of today's crayfish would then have ridden the slowly drifting landmasses north and south, eventually branching into numerous species as the continents continued to divide. However, to show conclusively that the ancestors of northern and southern crayfish once lived on a united Pangaea, even older fossils will be needed. Carrie Schweitzer is a geologist at Kent State University in Ohio. She said the alternative explanation—that freshwater crayfish evolved independently in the northern and southern continents—cannot yet be discarded. For drifting supercontinents to explain the origin of the different families, she said, "crayfish would have had to have invaded freshwater [habitats] really early and become widespread by the time Pangaea started to split. So far, we really don't have evidence of that." Early in AustraliaThe new fossils also provide clues about the origin of the numerous crayfish species found in Australia today. The fossil dates are consistent with results of recent genetic studies, which suggest that many new crayfish species began to appear in what is now Australia about 134 million years ago. At that time the continents of Australia, South America, and Antarctica were just starting to break off from the southern supercontinent of Gondwana. (See related photo: "'Polar Predator' Dino Tracks Found" [October 23, 2007].)Just as the breakup of Pangaea may have forever divided the two main crayfish lineages, Martin believes, the later splitting of Gondwana may have resulted in a surge in crayfish diversity. The early crayfish apparently thrived in a near-polar environment in southeastern Australia, and must have been adapted to cold water temperatures and freezing winters just like some modern crayfish species. "These crayfish were burrowing much like modern ones in the same area today, showing that their behaviors haven't changed that much in more than 100 million years," Martin said.
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ISI Fast Breaking Paper
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| Author:
M. Santosh et al.
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Date:
12/11/2008
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| Abstract |
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| http://www.elsevier.com/wps/find/P06.cws_home/fastbreakingpaperss |
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