On 31 January 2017, the journal Science published a news report describing two new (but independent) studies purporting to have successfully recovered original protein from 80- and 195-million year old dinosaur fossils, respectively — a remarkable feat in a field that had previously regarded a fossil that was a “mere” 68 million years old with skepticism:
Two new studies suggest that it is possible to isolate protein fragments from dinosaurs much further back in time than ever thought possible. One study, led by Mary Schweitzer, a paleontologist from North Carolina State University in Raleigh who has chased dinosaur proteins for decades, confirms her highly controversial claim to have recovered 80-million-year-old dinosaur collagen. The other paper suggests that protein may even have survived in a 195-million-year-old dino fossil.
Fossilization is the chemical replacement of biologic chemicals with inorganic minerals — a gradual process that, ultimately, removes the original material that composed the preserved organism. Extrapolation from basic chemical experiments suggest that original biomolecules have a half life of around a million years, meaning anything dinosaur-related (at least 65 million years old) would be expected to have been lost to time.
That’s why, in 2009, when North Carolina State University paleontologist Mary Schweitzer (who had already published a paper on the potential discovery of proteins in a 68 million year old Tyrannosaurus rex), published a study suggesting the preservation of proteins in an 80 million year old hadrosaur fossil, her findings were questioned:
[Scientists not involved in the research], however, raised several concerns. At the top of the list was the mass spectrometry data. The technique chops proteins into small snippets and then weighs them. By comparing the masses with those of known protein fragments, researchers can work out the amino acid sequences in the original protein fragments. But for some fragments in the samples, the mass signature was barely visible above the noise, lowering the statistical confidence in their proper identification.
In the first of the new studies highlighted (which was published in the Journal of Proteome research on 23 January 2017) Schweitzer aimed to allay these concerns by completely redoing the experiment with even more sensitive tools and an even more aggressive contamination prevention protocol. The results, once again, suggest that the proteins came from a dinosaur rather than contamination, per their study:
Here we used different methods of sample preparation, MS instrumentation, and data analysis, and conducted these analyses in a different laboratory space, separated by several years from [the 2009 study]. These peptides included two sequences that were recovered in both studies, making it highly unlikely that these identifications arose from contamination. Furthermore, phylogenetic analyses placed these sequences within Archosauria and revealed similarities to both crocodylians and basal birds, depending on which parts of the sequence were being analyzed.
These peptides, biologic building blocks that consist of two or more linked amino acids, are fragments from a kind of protein referred to as Type I collagen, the authors argue, which plays a role in everything from bone structure to tissue repair. The team compared these peptide sequences to those found in the collagen of extant turtles, reptiles and birds to see if they were consistent with a dinosaur origin.
Many who were initially skeptical of Schweitzer’s early work are now convinced:
The Schweitzer paper is a “milestone,” says ancient protein expert Enrico Cappellini of the University of Copenhagen’s Natural History Museum of Denmark, who was skeptical of some of Schweitzer’s earlier work. “I’m fully convinced beyond a reasonable doubt the evidence is authentic.”
The second study, headed by University of Toronto paleontologist Robert Reisz and published in Nature Communications, attempted to push the protein clock back even further. In this study, the authors described:
Evidence of protein preservation in a terrestrial vertebrate found inside the vascular canals of a rib of a 195-million-year-old sauropodomorph dinosaur, where blood vessels and nerves would normally have been present in the living organism.
Unlike the Schweitzer study, however, this investigation used a different approach, which they argued reduced the possibility of contamination:
In order to exclude the possibility of external contamination of the fossil material, […] in situ investigation of organic remains within the adult Lufengosaurus bones was undertaken using thin sections. FTIR spectroscopy is a state-of-the-art technique and non-destructive analysis method for identifying the vibrational motions of chemical bonding of molecular structures based on the characteristic infrared absorption bands in the mid-infrared range, associated with the various functional groups especially for organic molecules including proteins.
The discovery of dinosaur protein more than twice as old the earlier finds, however, has been met with more skepticism than the Schweitzer study. One person who is skeptical is Schweitzer herself, who commented on the work in a Christian Science Monitor report, saying that this method is indeed sensitive, but introduces new potential problems:
The interactions between molecules that the SR-FTIR microspectroscopy identifies are also bonds that exist in other compounds. Yes, some of those compounds are proteins, she says, but they also crop up in “other, non protein compounds … like glues and consolidants commonly applied to fossils in the field, or epoxies, such as the ones they embedded their material in to make the sections.”
Even if further studies cannot confirm the existence of 195 million year old protein, both studies highlight a turning point in the field of paleontology. In that 2009 report on Schweitzer’s study, Burke Museum paleontologist Tom Kaye stated “[Schweitzer’s 2009 results] will either be nothing or the biggest revolution in paleontology ever.” Now, in 2017, it’s looking more like a revolution:
Now that it seems that very ancient protein fragments can, in fact, be isolated and examined, it’s a safe bet that many new collaborations will soon take shape to pin down the evolutionary relationships among different dinosaurs, as well as among ancient mammals and other extinct creatures.
These results do not mean, however, that we can expect some kind of Jurassic Park situation anytime soon, Reisz told the Monitor:
“Jurassic Park” fans shouldn’t get too excited, though, Reisz says. Preserved organic material doesn’t mean there is DNA in dinosaur bones that scientists could use to clone the beasts like they do in the fictive tale. DNA has a half-life of about 521 years, according to previous research, which means that an organism’s DNA would be completely destroyed within 7 million years after its death.