Scientists have recovered protein from the 68-million-year-old bone of a Tyrannosaurus rex, an unprecedented discovery that could change the way the remains of the extinct animals are studied.
The successful extraction of the fibrous protein collagen from the interior of a bone unearthed in Montana is the oldest organic sample recovered from fossilized remains, according to the authors of a paper to appear in Friday's issue of the journal Science.
The identification of these sequences also lends further evidence to the theory that modern birds are descended from dinosaurs.
Previous studies had suggested proteins and more complex organic matter such as DNA could not survive for more than a million years because of cellular degradation over time.
The oldest previously identified protein came from mammoths that died about 300,000 years ago, while the oldest recovered DNA samples were found in Neanderthal remains that are 30,000 to 50,000 years old.
The large bone sample from the T. rex had proven particularly resistant to degradation, according to North Carolina State University researcher Mary Schweitzer, one of the leaders of two research groups who authored the paper.
Schweitzer had previously discovered soft tissue in the same leg bone, first uncovered from the Hell Creek formation in Montana in 2000 by paleontologist Bob Harmon.
Working with another team, led by Lewis Cantley and John Asara from Harvard Medical School, Schweitzer was able to analyze and identify the protein found in the bone using a mass spectrometer, a sensor that can break down and identify individual molecules based on their mass and charge.
They discovered the protein in the bone was collagen, a fibrous and durable protein that gives bones their structure and flexibility.
"From a paleo standpoint, sequence data really is the nail in the coffin that confirms the preservation of these tissues," Schweitzer said in a statement Thursday. "This data will help us learn more about dinosaurs' evolutionary relationships, about how preservation happens, and about how molecules degrade over time."
Abetter understanding of molecular degradation could have medical implications for the treatment of disease, she added.
Links to birds, amphibians
The identification of the sequences also lends further evidence to the hypothesis that modern birds are descendants of dinosaurs.
The scientists were able to identify seven different dinosaur protein sequencesfrom the bone and compared them to the sequences of modern species.
Three matched the sequences of chickens, one matched a protein from a newt and another, a proteinfrom a frog. Two others matched several species, including both chickens and salamanders.
"Most people believe that birds evolved from dinosaurs, but that's all based on the architecture of the bones," Asara said. "This allows you to get the chance to say, 'Wait, they really are related because their sequences are related.' We didn't get enough sequences to definitively say that, but what sequences we got support that idea."
"The fact that we are getting proteins is very, very exciting," said Jack Horner of Montana State University and the Museum of the Rockies, whowasa member of the original dig team that found the bones and isa co-author of the Science paper.
The protein evidence also "changes the idea that birds and dinosaurs are related from a hypothesis to a theory," Horner added.
His museum is organizing nine different field crews involving more than 100 people to search for fossils in Montana and Mongolia in the hopes of turning up further organic material, he said.