Last week, a little movie called Jurassic World debuted. You might have heard something about it. Paleontologists certainly have been jawing about it for a while, particularly how the movie’s dinosaurs stack up against the actual animals emerging from the rock.* But all the arguments about enfluffled dinosaurs and bunny hands have missed a more fundamental issue – could scientists ever recover enough intact dinosaur goo to populate a real Jurassic World?
When the first Jurassic Park premiered in 1993, finding non-avian dinosaur DNA seemed a certainty. Two days before the official release of the movie Raúl Cano and colleagues announced that they had sequenced the DNA of a 135-120 million year old, amber-encased weevil. That was old enough to suggest that tatters of DNA from Cretaceous dinosaurs might be found, and, a little more than a year later, S.R. Woodward and colleagues announced that they had sequenced DNA from an 80 million year old dinosaur bone fragment. It seemed that life had found a way.
But as researchers refined the techniques required for ancient DNA analysis, they began to realize that many of these earlier announcements were too good to be true. Geneticists could carefully retrieve and study the DNA of relatively recent organisms – moas, cave bears, Neanderthals, and more – but genetic material is too fragile to last for tens of millions of years. The truly ancient sequences often turned out to be contamination from modern sources – part of the growing pains of developing this new branch of science.
The sad truth is that we’re not likely to ever recover Mesozoic DNA. Not unless there’s some undiscovered mode of preservation that can keep a creature’s genome from going to pieces. But dinosaur blood is another matter. In 2005 Mary Schweitzer and colleagues announced that they had found remnants of blood vessels in a thigh bone from Tyrannosaurus. Four years later, Schweitzer and coauthors described other soft tissue tidbits from the hadrosaur Brachylophosaurus. These weren’t fresh flesh. They had been altered over the course of time. Nevertheless, they seemed to retain some original soft tissue and revealed some details of the small and the squishy within saurians.
And now, just in time for the release of Jurassic World, Sergio Bertazzo, Susannah Maidment, and colleagues have offered a look at possible 75 million year old dinosaur blood cells. The researchers didn’t pop the champagne on first sight of the microscopic structures. There were other possible explanations. Perhaps someone had accidentally bled on the fossil while it was in storage, for example. (Stranger things have happened in museum collections.) But through visual and biochemical investigations, the researchers were able to rule out human contamination. Additional studies will hopefully test the idea, but, for now, there’s a good chance that the scrappy bones at the center of the study really do preserve some degraded dino blood.
This wasn’t an isolated find. Out of eight dinosaur bones the researchers examined, they found some kind of soft tissue structure – be it blood cells, collagen fibers, or unknown carbon-rich structures – in six of them. This came as a shock. The bones were fragments. The sort of scrap curators are ok with paleontologists using for “consumptive analysis” because they’re unremarkable and often unidentifiable beyond the skeletal element. If these humble fossils could preserve the remains of soft tissues, Bertazzo and coauthors wonder, what about fossils that are heralded as exceptionally-preserved? Paleontologists should have a much closer look at their most prized fossils.
[Scanning electron micrographs and 3D reconstructions from serial sections of blood cell-like structures. Credit: Bertazzo et al., Nature Communications.]
This area of research is still new, but, with more samples, paleontologists may have a new way to investigate the biology and physiology of extinct creatures. Soft tissue preservation may be more widespread than anyone expected, and controversies such as “Were dinosaurs endotherms?” might start to creep closer to resolution. Along with related subfields like histology – the study of bone microstructure – investigations of dinosaur soft tissues hold the most potential to refine our understanding of how these animals really lived.
In order to get more samples paleontologists need to think carefully about how they excavate and preserve fossils. Dinosaur bones are incredibly fragile fossils. In the field, volunteers and scientists douse them with consolidants and sometimes glue broken pieces back together to make sure the bones make the journey back to the prep lab. How these chemical changes might alter, or even destroy, soft tissue clues isn’t yet known, and the realization that soft tissue preservation might be a common phenomenon means that field workers, lab techs, and curators will have to figure out new ways to preserve not only the external anatomy of a bone, but also the secrets held within.
Even as specialists wrestle with these questions, though, the new research from Bertazzo and Maidment underscores how even a sliver of fossil bone can be incredibly informative. An unidentified shard of dinosaur bone isn’t just a throwaway fossil. It’s part of a real animal that was born, grew, was shaped by natural history, perished, and was locked in stone. Knowing the right questions to ask, and the proper tools to use, can unleash unexpected conclusions from even the scrappiest fossil. And even if we’re never going to see a real Jurassic World, such finds may help paleontologists better understand and more accurately reconstruct the creatures that we love to see tear across the silver screen.
*Full disclosure: I was the science adviser for the film’s official website.
Bertazzo, S., Maidment, S., Kallepitis, C., Fearn, S., Stevens, M., Xie, H. 2015. Fibres and cellular structures preserved in 75-million-year-old dinosaur specimens. Nature Communications. doi: 10.1038/ncomms8352
Cano, R., Poinar, H., Pieniazek, N., Acra, A., Poinar, G. 1993. Amplification and sequencing of DNA from a 120-135-million-year-old weevil. Nature. 363: 536-538. doi: 10.1038/363536a0
Pääbo, S. Poinar, H., Serre, D., Jaenicke-Despres, V., Hebler, J., Rohland, N., Kuch, M., Krause, J., Vigilant, L., Hofreiter, M. 2004. Genetic analyses from ancient DNA. Annual Review of Genetics. 38: 645-679. doi: 10.1146/aanurev.genet.37.110801.143214
Schweitzer, M., Wittmeyer, J., Horner, J., Toporski, J. 2005. Soft-tissue vessels and cellular preservation in Tyrannosaurus rex. Science. 307, 5717: 1952-1955. doi: 10.1126/science.1108397
Woodward, S., Weyand, N., Bunnell, M. 1994. DNA sequence from Cretaceous period bone fragments. Science. 266, 5188: 1229-1232. doi: 10.1126/science.7973705