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Topic: virus: Technique Dates Skeleton Back 4M Years (Read 427 times) |
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Walter Watts
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virus: Technique Dates Skeleton Back 4M Years
« on: 2003-04-25 12:36:24 » |
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Technique Dates Skeleton Back 4M Years
Apr 24, 4:47 PM (ET)
By PAUL RECER
WASHINGTON (AP) - A new dating technique suggests that a human-like
fossil skeleton found in South Africa was buried about 4 million years
ago, which makes it one of the oldest known hominid discoveries.
That's 1 million years earlier than previously thought.
The nearly complete skeleton came from the Sterkfontein caves that
contain rich deposits of remains from the pre-human branches of the
ancestral tree that led to modern humans. The bones are identified as a
type of Australopithecus, an extinct form of pre-humans.
Skeleton fossils unearthed in 1997 were age dated at about 3 million
years using a technique that measured the changes in the Earth's
magnetic field geochemically recorded within rocks found with the
fossils. The results had been disputed by experts who said the method
was not precise.
In the new effort, researchers, led by Darryl E. Granger and M.W. Caffee
of Purdue University, measured the decay of isotopes in cave sediments
to establish the older ages. A report on their study appears Friday in
the journal Science.
The new technique is based on chemical changes in elements caused by
cosmic rays. The bombardment of cosmic rays creates unstable isotopes of
beryllium and aluminum, both of which decay at a known rate. The older a
sediment is, the more isotopes it acquires. When the sediments are
buried by an earth movement, the cosmic ray bombardment stops, but the
isotopic decay continues.
Granger said that the cave is carved by water out of dolamite and cherte
rock. Over time, both the fossils and fragments of quartz crystals that
were on the surface were washed into the cave and deposited together.
Once the quartz is inside the cave, it is no longer being hit by cosmic
rays.
"That sets the clock," said Granger.
He said by measuring the isotopic decay in the quartz, the researchers
could establish when both the fossils and the quartz were deposited.
The other co-authors of the study are T. C. Partidge and R. J. Clarke,
both of the University of the Witwatersrand in Johannesburg, South
Africa. Partridge and Clark did the earlier studies on the Sterkfontein
fossils.
Australopithecus is an extinct hominid species that lived from about 4
to 2.5 million years ago. Lucy, a famed pre-human fossil find found in
Ethiopia, was identified as a type of Australopithecus. The new age
dating technique suggests that the fossils from Sterkfontein Cave are
even older than Lucy.
Granger said only an Australopithecus fossil found in Kenya is older
than the remains from the South African cave.
However, some researchers said in Science that the specimens used by
Granger and Caffee may have been contaminated by debris that was not
deposited at the same time as the fossils.
Henry Schwarez of McMaster University in Hamilton, Canada, said in
Science that the collapsed cave ceilings may have dropped sediments into
the area where the fossils were found and thus distorted the age-dating
results. Schwarez said that the Purdue researchers need to test the
technique using sediments from South African caves of a known age.
Granger said the age-dating technique is not affected by sediments from
inside the cave. He said the cave minerals are distinctly different from
the quartz washed in from the surface. The material from the cave walls
and ceiling is separated from the quartz before the isotopic
measurements are taken, he said.
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On the Net:
Science: www.sciencemag.org
--
Walter Watts
Tulsa Network Solutions, Inc.
"No one gets to see the Wizard! Not nobody! Not no how!"
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Walter Watts
Tulsa Network Solutions, Inc.
No one gets to see the Wizard! Not nobody! Not no how!
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ElvenSage
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Re:virus: Technique Dates Skeleton Back 4M Years
« Reply #1 on: 2003-04-25 12:55:15 » |
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Awesome! Thanks for all the great material you post on here Walt! =)
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Safe from the pain and truth and choice and other poison devils
See.. they don't give a fuck about you, like i do.
Just stay with me, safe and ignorant,
Go back to sleep
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