The T-rex Collagen Controversy

Soft Tissue, Blood Vessels and Blood Cells in a T-rex Femur?
Mary SchweitzerJack Horner and others made headlines in 2005 when she reported soft organic tissue deep within the femur of a Tyrannosaurus rex (Fig. 1). MSNBC, Scientific American and National Geographic covered this story on the web.

Tyrannosaurus

Figure 1. Tyrannosaurus, the dinosaur at the center of the controversy.

The Creationists jumped all over this news  asserting that T-rex was much, much younger.

Here I offer a belated tip of the hat to friend and fellow heretic, Tom Kaye, who showed me his heretical work several years ago while still living in Chicago. Let me state from the start, I’m only pushing competing hypotheses together here. I have not done the testing to weigh in on one side or the other.

Maybe Not…
Kaye, Gaugler and Sawlowicz (2008) reinterpreted the purported collagen as bacterial biolfilms. They reported, “Mineralized and non-mineralized coatings were found extensively in the porous trabecular bone of a variety of dinosaur and mammal species across time. They represent bacterial biofilms common throughout nature. Biofilms form endocasts and once dissolved out of the bone, mimic real blood vessels and osteocytes. Bridged trails observed in biofilms indicate that a previously viscous film was populated with swimming bacteria. Carbon dating of the film points to its relatively modern origin. A comparison of infrared spectra of modern biofilms with modern collagen and fossil bone coatings suggests that modern biofilms share a closer molecular make-up than modern collagen to the coatings from fossil bones. Blood cell size iron-oxygen spheres found in the vessels were identified as an oxidized form of formerly pyritic framboids.” 

This represents a more conservative and rational explanation for the collagen-like structures found in fossil bone. Kaye says that his team was denied access to the original bone, and that continues to this day. Others are in line ahead of him, is what he hears.

When This News Came Out
Several blogs weighed in on the find of the century now reduced to a major controversy. Smithsonian.com reported on both sides of the controversy, concluding, “Personally, I’m leaning toward believing in the extraordinary.” …and Occam’s Razor just took a walk.

Carl Zimmer.com reported, “Schweitzer’s tubes and osteocytes, they argue, are not blood vessels or cells but biofilms formed by bacteria that invaded the fossils after death. In a paper published Monday in the journal PLoS ONE, Kaye and colleagues report that carbon dating of one sample shows that the tubes are at most a few decades old and that their infrared spectra give a closer match to bacterial biofilms than to collagen. Troughs in the walls of the tubes resemble the track a microbe would make crawling through a biofilm, they note. ‘We think that’s one of the smoking guns,’ Kaye says.”

Contradicting Kaye’s Team and Supporting Schweitzer’s Conclusion…
Peterson, Lenczewski and Scherer 2010 reported, “The identification of biomolecules in fossil vertebrate extracts from a specimen of Brachylophosaurus canadensis has shown the interpretation of preserved organic remains as microbial biofilm to be highly unlikely. Results of the study indicate that the crystallization of microbial biofilms on decomposing organic matter within vertebrate bone in early taphonomic stages may contribute to the preservation of primary soft tissues deeper in the bone structure.

And Another… 
San Antonio et al. (2011) reported, “Functionally significant regions of collagen fibrils that are physically shielded within the fibril may be preferentially preserved in fossils. This non-random distribution supports the hypothesis that the peptides are produced by the extinct organisms and suggests a chemical mechanism for survival.”

Then Salzberg et al. (2011) Struck Back with Metagenomics…
In their JVP abstract Salzberg et al. (including Tom Kaye, 2011) recovered  a full characterization of the DNA from a section of Brachylophosaurus canadensis fossil using ‘Metagenomics’ techniques. Soft tissue structures similar to those reported as dinosaurian blood vessels and bone cells were observed providing the platform for analyzing the molecular content of this fossil further. Metagenomics data identified ALL the DNA in the sample giving proportionate ranks to the various molecular species therein. The sample was processed to isolate organic remnants from the intravascular cavities of the fossil’s cortical bone, in order to exclude possible contaminants from the bone surface. DNA from various species of bacteria, plants, fungi, and chordates was detected in the bone. Some modern bird DNA was also found. The presence of modern DNA provided an obstacle to identifying ancient dinosaur molecules. The bacterial DNA provided support for the production of biofilms over the 80-million-year age of the fossil.

The Salzberg findings also came up with a more complete proteome of the ostrich and the previously reported “T. Rex proteins” now found a perfect match in the ostrich sequence suggesting contamination on Schweitzer’s part. The same was true of unreported hemoglobin proteins in the Schweitzer data that also turned out to be a perfect match to ostrich.

A Paleo Fight
There is a paleontological fight going on here. Both opposing hypotheses can’t be right. The opposing forces need to get together and not wait several years between successive arguments. Heretics are sometimes right. Those who test assertions should be considered.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Kaye TG, Gaugler G and Sawlowicz 2008. Dinosaurian Soft Tissues Interpreted as Bacterial Biofilms. PLoS ONE 3(7): e2808. doi:10.1371/journal.pone.0002808
Peterson JE, Lenczewski ME, Scherer RP 2010. Influence of Microbial Biofilms on the Preservation of Primary Soft Tissue in Fossil and Extant Archosaurs. PLoS ONE 5(10): e13334. doi:10.1371/journal.pone.0013334
Salzberg S et al. 2011 abstract. DNA, dinosaurs and metagenomics: a new tool for mass identification of DNA from fossil bone. Journal of Vertebrate Paleontology abstracts 2011.
San Antonio JD, Schweitzer MH, Jensen ST, Kalluri R, Buckley M, et al. 2011. Dinosaur Peptides Suggest Mechanisms of Protein Survival. PLoS ONE 6(6): e20381. doi:10.1371/journal.pone.0020381
Schweitzer MH, Wittmeyer JL, Horner JR, Toporski JK 2005. Soft-tissue vessels and cellular preservation in Tyrannosaurus rex. Science 307: 1952–1955.

Advertisements

One thought on “The T-rex Collagen Controversy

  1. TPH, thanks for a great blow-by-blow. In Sept. I saw Salzberg reply similarly as above on a PZ Myers blog. I can’t find his 2011 paper that you referred to. Is it possible to get a pdf of it?

    Thanks! And may the best man (or explanation) win.

    BobEnyart@gmail.com
    RealScienceFriday.com

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s