Then, in 2007, Schweitzer and her colleagues analyzed the chemistry of the T. rex proteins. They found the proteins really did come from dinosaur soft tissue. The tissue was collagen, they reported in the journal Science, and it shared similarities with bird collagen - which makes sense, as modern birds evolved from theropod dinosaurs such as T. rex.
The researchers also analyzed other fossils for the presence of soft tissue, and found it was present in about half of their samples going back to the Jurassic Period, which lasted from 145.5 million to 199.6 million years ago, Schweitzer said.
"The problem is, for 300 years, we thought, 'Well, the organics are all gone, so why should we look for something that's not going to be there?' and nobody looks," she said.
The obvious question, though, was how soft, pliable tissue could survive for millions of years. In a new study published today (Nov. 26) in the journal Proceedings of the Royal Society B: Biological Sciences, Schweitzer thinks she has the answer: Iron.