New tests reveal controversial dinosaur DNA isn't so ancient after all
In 2008, researchers analyzed samples of protein found preserved for 68 million years inside a T-rex leg bone, and came to the conclusion that the dinosaurs were closely related to modern chickens and ostriches. Now, palaeontologists from the University of Manchester have taken another look at the tissue, and found that it's an even closer match to ostriches than previously thought – because it is ostrich, thanks to some modern contamination.
While there's plenty to learn about extinct species from fossilized bone, on rarer occasions soft tissues like brains and feathers are preserved, giving palaeontologists a whole new level of insight. The discovery of intact collagen peptides understandably caused a stir – at 68 million years old, these samples were far older than the 3.5 million years that is generally thought to be the limit for collagen. The find allowed scientists to slot the T-rex into the overall family tree, somewhere between alligators and ostriches.
But the announcement wasn't without controversy at the time, with some critics arguing that contamination in the lab, either from bacteria or modern bones, could have returned false positives. And after studying the samples a little more closely, the Manchester team believes that's exactly what happened, dashing any hopes of fact following fiction.
The researchers analyzed bone samples from three different ostrich specimens, and found that the peptides strongly matched those in the T-rex fossil, as well as other collagen samples that the team found later in Brachylophosaurus bones. It makes sense, the team says, given that the original tests were run in a lab that also worked with ostrich bones.
"Our work set out to identify the collagen fingerprints for both ostrich and alligator and was not intending to debunk the previous studies," says Dr. Mike Buckley, lead researcher on the study. "However, we soon realized that our results were pulling the rug from beneath the paradigm that collagen might survive the ravages of deep time."
While it might be a disappointing discovery for scientists (or Jurassic Park fans), the study goes to show that these kinds of important finds need to be properly verified before any sweeping claims are made. Since the instruments used are highly sensitive, the dinosaur bones need to be properly isolated from any modern contaminants.
"The fossil record is offering new information on a daily basis through the application of new technology, but we must never forget that when results show us something that we really want to see, that we make sure of our interpretation," says Phil Manning, co-author of the study. "The alleged discovery of protein sequences in dinosaur bones has led many unsuccessful attempts to repeat these remarkable claims. It seems we were trying to reproduce something that was beyond the current detection limits of our science."
While we shouldn't hold our breath for a real-world Jurassic Park, there is still hope in the fantasy of reviving extinct species. Dinosaurs are way too old to contain viable DNA samples, but teams are considering how to bring back more recently-extinct creatures like the woolly mammoth, the dodo or the thylacine – but then again, to paraphrase the movie, just because we could, doesn't mean we should.
Source: University of Manchester