For the first time, researchers have read what they say is the biological signature of a tyrannosaur — a signature that confirms the increasingly accepted view that modern birds are the descendants of dinosaurs.
The signature doesn't come from studying the shape of the 68 million-year-old dinosaur's fossilized bones, but from analyzing the organic material found inside those bones. It's not DNA — despite what you've seen in movies like "Jurassic Park," that genetic material couldn't be recovered. But researchers say it's the next-best thing: collagen proteins that were isolated using techniques on the very edge of what's possible today.
Those techniques, detailed in Friday's issue of the journal Science, could open up "a new window into an entirely new approach" for paleontology, one expert told MSNBC.com. What's more, researchers say the methods are already being incorporated into improved tools for detecting present-day diseases.
“We don’t know what the possibilities are,” said Mary Schweitzer, a paleontologist at North Carolina State University and the North Carolina Museum of Natural Sciences who was one of the principal authors behind the studies. “We’re starting right now with a particular goal in mind, but the spin-offs … how this might apply to human health and our understanding of disease … all of that is yet to be seen.”
Schweitzer and her colleagues emphasized that the protein analysis was just the first step in what could become a worldwide effort to categorize extinct species according to their molecular makeup. Famed paleontologist Jack Horner, another member of the research team, said he would embark on a world-girdling series of expeditions this summer to see if further samples could be found.
“All of our morphological hypotheses based on fossils need to be tested. Every one of them,” said Horner, a paleontologist at Montana State University and the Museum of the Rockies.
Tale of a T. rexThe tale of the T. rex began with Horner, back in 2003: He and his team found the tyrannosaur's massive leg bone beneath 1,000 cubic yards of rock at the Hell Creek fossil site in Montana, but had trouble fitting the bone inside their helicopter for the airlift back to the lab.
When they broke the bone into pieces for transport, they were amazed to find that some of the dinosaur's soft tissues appeared to be preserved within. Previously, paleontologists had thought all the tissues of a fossil turned to minerals over the course of millions of years.
After analyzing the tissues under a microscope, Schweitzer reported in 2005 that they looked similar to the cells and blood vessels found in ostrich bones. But at that time, "we could not directly address what that material was made of," she said during a teleconference with journalists this week.
Schweitzer suspected that some of the material was preserved collagen protein — which is the main organic constituent of bone, left behind when the minerals are removed. She said the material looked like collagen, and it reacted like collagen when chicken antibodies were applied to a sample.
But to confirm her suspicions, Schweitzer turned to John Asara, a specialist in mass spectrometry at Harvard Medical School and Beth Israel Deaconess Medical Center. Mass spectrometry is a technique for identifying minute quantities of a substance by measuring its atomic properties, molecule by molecule. Asara and Schweitzer had worked together previously to isolate protein sequences from mammoth remains that dated back 100,000 to 300,000 years.
The T. rex task was much more challenging: After removing the minerals and impurities from the bone samples that Schweitzer provided, Asara had less than a billionth of a gram of protein to work with. Nevertheless, he and his colleagues were able to decode seven strings of protein molecules. Those sequences were compared with a large database of collagen data — including sequences that Asara and his team isolated from a modern ostrich and from mastodon bone fragments that were 160,000 to 400,000 years old.
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