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Okay we've humored the science deniers long enough. Time for a palette cleanser.
New instrument dates old skeleton Little Foot 3.67 million years old
"New instrument dates old skeleton—'Little Foot' 3.67 million years old
Little Foot is a rare, nearly complete skeleton of Australopithecus first discovered 21 years ago in a cave at Sterkfontein, in central South Africa. The new date places Little Foot as an older relative of Lucy, a famous Australopithecus skeleton dated at 3.2 million years old that was found in Ethiopia. It is thought that Australopithecus is an evolutionary ancestor to humans that lived between 2 million and 4 million years ago.
The dating relied on a radioisotopic dating technique pioneered by Granger coupled with a powerful detector originally intended to analyze solar wind samples from NASA's Genesis mission. The result was a a relatively small margin of error of 160,000 years for Little Foot and 210,000 years for the stone tools.
The technique, called isochron burial dating, uses radioisotopes within several rock samples surrounding a fossil to date when the rocks and the fossil were first buried underground.
The burial dating relies on measuring radioactive isotopes aluminum-26 and beryllium-10 in quartz within the rock. These isotopes are only created when the rock is exposed to cosmic rays. When a rock is on the surface, it builds up these isotopes. When it is buried or deposited in a cave, the isotopes decay at known rates. The ratio of the remaining aluminum-26 and beryllium-10 can be used to determine how long the rock has been underground, Granger said.
A graph of the isotope ratios, called an isochron, is created for the rock samples. If a strong isochron line forms, it increases the confidence that the samples on the line meet the criteria to be good candidates for accurate dating. Samples that have been compromised, due to reburial or natural movement of sediment within a site, fall above or below the line can be tossed out of the analysis, Granger said.
"If we had only one sample and that rock happened to have been buried, then re-exposed and buried again, the date would be off because the amount of radioisotopes would have increased during its second exposure," he said. "With this method we can tell if that has happened or if the sample has remained undisturbed since burial with the fossil. It is expensive and a lot of work to take and run multiple samples, but I think this is the future of burial dating because of the confidence one can have in the results.""
New instrument dates old skeleton Little Foot 3.67 million years old
"New instrument dates old skeleton—'Little Foot' 3.67 million years old
Little Foot is a rare, nearly complete skeleton of Australopithecus first discovered 21 years ago in a cave at Sterkfontein, in central South Africa. The new date places Little Foot as an older relative of Lucy, a famous Australopithecus skeleton dated at 3.2 million years old that was found in Ethiopia. It is thought that Australopithecus is an evolutionary ancestor to humans that lived between 2 million and 4 million years ago.
The dating relied on a radioisotopic dating technique pioneered by Granger coupled with a powerful detector originally intended to analyze solar wind samples from NASA's Genesis mission. The result was a a relatively small margin of error of 160,000 years for Little Foot and 210,000 years for the stone tools.
The technique, called isochron burial dating, uses radioisotopes within several rock samples surrounding a fossil to date when the rocks and the fossil were first buried underground.
The burial dating relies on measuring radioactive isotopes aluminum-26 and beryllium-10 in quartz within the rock. These isotopes are only created when the rock is exposed to cosmic rays. When a rock is on the surface, it builds up these isotopes. When it is buried or deposited in a cave, the isotopes decay at known rates. The ratio of the remaining aluminum-26 and beryllium-10 can be used to determine how long the rock has been underground, Granger said.
A graph of the isotope ratios, called an isochron, is created for the rock samples. If a strong isochron line forms, it increases the confidence that the samples on the line meet the criteria to be good candidates for accurate dating. Samples that have been compromised, due to reburial or natural movement of sediment within a site, fall above or below the line can be tossed out of the analysis, Granger said.
"If we had only one sample and that rock happened to have been buried, then re-exposed and buried again, the date would be off because the amount of radioisotopes would have increased during its second exposure," he said. "With this method we can tell if that has happened or if the sample has remained undisturbed since burial with the fossil. It is expensive and a lot of work to take and run multiple samples, but I think this is the future of burial dating because of the confidence one can have in the results.""
