While people like [Pavel Pevzner] pour over the data, [Mary Schweitzer] and [John Asara] steadfastly defend their work and conclusions. Schweitzer says [Thomas Kaye]'s alternative biofilm explanation is irrelevant -- partly because he wasn't working on the actual dinosaur specimen, but also because, "Tom did not demonstrate that modern biofilm will colonize vascular channels within bone. It does indeed grow over glass slides in a solution, but that is not the same thing."

"When you come up with an extraordinary explanation for something like dinosaur proteins surviving millions of years, you need extraordinary proof as well," said [Steven Salzberg]. "I don't think that exists here. The authors haven't provided a reason why it would survive, and there are far, far more plausible explanations why it wouldn't."

7 PICS; 1. From this 68 million-year-old femur of a Tyrannosaurus rex, Mary Schweitzer of North Carolina State University and colleagues say they extracted soft tissue with surviving proteins that match those of modern-day birds. 2. Thomas Kaye of the University of Washington suggested that the purported soft tissue might actually be bacterial slime. In this scanning electron microscopic image, arrows point to biofilm coatings peeling away from vascular canal walls of fossilized bone. The coatings are the product of bacteria and not original organic material. 3,4. UNDER THE MICROSCOPE -- Schweitzer reported that a microscopic image of tissue from inside a T. rex bone shows a vascularlike structure containing spheres resembling red blood cells. But Kaye countered that a fossil about the same age (lower) shows similar tubular structures containing spheres that are actually inorganic iron oxide framboids. 5. Until paleontologist Mary Schweitzer and colleagues reported finding T. rex proteins, the oldest known surviving proteins came from a mastodon fossil less than 1 million years old. 6. Computational biologist Pavel Pevzner at UCSD says reports matching T. rex proteins to those of modern birds lacked sufficient, published proof. 7. Using mass spectrometry, John Asara, a Harvard University pathologist, reported he had matched surviving T. rex proteins to those of modern-day chickens. Thomas Kaye of the University of Washington offered alternative explanations for the soft-tissue findings. "It's quite a mess," Kaye said of the dispute. [1. Science 5. North Carolina State University 6. UCSD Jacobs School of Engineering 7. Harvard University 8. University of Washington]