Scientists have extracted tiny bits of protein from a 68 million-year-old dinosaur fossil, a feat once thought biologically impossible. Close study of the protein's composition shows that the long extinct animal is most closely related to chickens. David McAlary reports that it is the first chemical evidence of a dinosaur link with birds.
Until now, the oldest protein to be extracted from bones was collagen from a 300,000-year-old mammoth. Collagen is a strong rope-like molecule that is the main component of bone and connective tissue like ligaments and tendons. Now the same scientist who reported that finding five years ago - North Carolina State University biologist Mary Higby Schweitzer - has found seven bits of collagen in a 68-million-year-old well preserved Tyrannosaurus rex bone.
The finding, reported in two papers in the journal Science, defies a long-standing assumption. Protein begins to degrade immediately after an animal dies and it was believed that after a million years, none is left.
But Schweitzer credits the discovery to an extremely sensitive laboratory technique called mass spectroscopy that can analyze minute bits of tissue that would otherwise go unnoticed.
"The data from both papers support the hypothesis that original protein may be preserved, but at such low levels they are barely detectable and in fact, without increases in technology, would not be detectable now" she said.
When Schweitzer's colleagues at Harvard Medical School analyzed the seven dinosaur proteins, they found that it most closely matches that in modern chickens. The Harvard researcher who led the inspection, John Asara, says the scientists did not get enough samples to prove the controversial notion that birds evolved from dinosaurs. But he says the observation offers molecular backing for the bird-dinosaur link, a claim supported until now only by similarities in the architecture of the two species' bones.
"As far as the significance, in my opinion, is, what we can do with these sequences now is we can start to think of the evolutionary biology and we can start to better create relationships between extinct and living organisms based on protein sequences," he said.
The technology to do this is in its infancy, and the researchers foresee eventual benefits from it in areas besides evolutionary biology. Mary Higby Schweitzer sees applications in medicine. For example, analysis of tiny snippets of proteins might reveal mutations that could lead to cancer tumors in people.
"We do not know what the possibilities are," she said. "We are starting right now with a particular goal in mind, but how this might apply to human health and our understanding of disease - I mean, all of that is yet to be seen."