A US researcher is claiming to have found further evidence that ancient dinosaur proteins – and even DNA – may have been preserved until the present day.
Dr Mary Schweitzer, professor of marine, earth and atmospheric sciences at the North Carolina Museum of Natural Sciences, is no stranger to controversy: she was the first person to discover what appeared to be preserved soft tissue in a T Rex bone fragment twenty years ago.
Since then, research has revealed similar preservation in an 80-million-year-old Brachylophosaurus canadensis, with the fibrous material turning out to be collagen, she says.
But many paleontologists have poured scorn on these claims, suggesting that the material is instead the result of contamination, and simply a biofilm of bacteria.
Now, though, Schweitzer says she’s gone a long way to disproving this. Using microscopy, histochemistry and mass spectrometry, she’s found that the structures react to specific antibodies, including one – a protein known as PHEX – that is found in the bone cells of living birds.
“The PHEX finding is important because it helps to rule out sample contamination,” she says. “Some of the antibodies that we used will react to proteins found in other vertebrate cells, but none of the antibodies react to microbes, which supports our theory that these structures are surviving osteocytes.”
Further, she says, the antibody to PHEX will only recognize and bind to one specific site only found in mature bone cells from birds.
“These antibodies don’t react to other proteins or cells. Because so many other lines of evidence support the dinosaur/bird relationship, finding these proteins helps make the case that these structures are dinosaurian in origin,” she says.
Most controversially of all, Schweitzer and her team also tested for the presence of DNA within the cellular structures, using an antibody that only binds to the ‘backbone’ of DNA – and found that it reacted to small amounts of material within the ‘cells’ of both the T. rex and the B. canadensis.
To rule out the presence of microbes, they used an antibody that binds histone proteins – which bind tightly to the DNA of everything except microbes – and got another positive result. They then ran two other histochemical stains which fluoresce when they attach to DNA molecules. These tests, too, were positive.
This, she says, strongly suggests that the DNA is original, although without sequence data it can’t be confirmed as dinosaurian.
For someone trying to settle controversy, this is a startling claim – especially as recent research into rates of DNA decay strongly indicates that it can’t last more than a few million years at most. Schweitzer, though, is confident.
“The data thus far seem to support the theory that these structures can be preserved over time,” she says. “Hopefully these findings will give us greater insight into the processes of evolutionary change.”