The Soft Tissue Saga

The topic of soft dinosaur tissue has been doing the rounds again, and so it could be useful to explain some of the details about this topic. Very briefly, this is what the issue is about:

Mary Schweitzer is a palaeontologist who discovered remnants of soft tissue in fossilised dinosaur remains. The science community has viewed her research as extraordinary, because it has opened the door to new discoveries about preservation and decay. Meanwhile, certain religious organisations have used her research to assert that dating methods are wrong, because soft tissue couldn’t possibly last as long as she says.

So, the question is this: Does her research show that dating methods are wrong, because there couldn’t possibly be soft tissue after 60million years; or, does her research show that there are situations in which tissue remnants can be persevered for extraordinarily long periods of time?

Let’s look into this further…

Mary Schweitzer’s journey into this research started in 1992 after she had recently graduated and was working in a laboratory. She was preparing microscope slides of a 60-million year old Tyrannosaurus rex specimen, and discovered what appeared to be blood cells. Her mentor (renowned palaeontologist Jack Horner) asked her what she thought she was seeing, and she replied, “Well, I know they can’t be blood cells, but they’re in the right place, the right location, the right size, and they’re nucleated.” He challenged her to prove they were not red blood cells. So she set out to prove they weren’t – and that effort led to her PhD. ⁠[1]

By doing various tests she found that somewhere in the fossil bones were compounds that were consistent with heme, which is a small, relatively stable iron-containing molecule that gives blood its red colour, and is the key oxygen-carrying component of the hemoglobin protein. (This bit about ‘iron-containing molecules’ is important – we’ll come back to that later.) She published her research in 1997, explaining her conclusions that the T.rex fossil contained fragments of hemoglobin molecules (not actual blood cells).

Schweitzer continued to do more of this research, and soft tissue topic surfaced again in 2005, when Schweitzer and her co-authors reported the discovery of intact blood vessels and other soft tissues in bone from a 65-million-year-old specimen of T.rex [⁠2]. As before, scientists were initially skeptical of these findings, as no-one ever imagined soft tissue could survive this long; and although some researchers attempted alternative explanations⁠ [3], these were never successfully substantiated, and Schweitzer’s research stood.

Schweitzer kept on investigating how it could be possible for rock-hard fossils that are tens of millions of years old, to have remnants of soft tissues inside them. It must be noted that at no stage has her research ever provided anything that would cast doubt on established dating methods. For example, the samples used for her 2005 paper are from one of the better dated dinosaur bones known to exist. The age of this bone is based on 86 separate chemical analyses on three different kinds of minerals, based on four independent radiometric decay series [4]. The dinosaur they were studying came from the Hell’s Creek Formation, which is one of the more famous and intensely studied dinosaur fossil sites spreading across areas of Montana, South Dakota, and North Dakota. This area and its fossils have been rigorously and independently dated on numerous occasions, always producing the same consistent results.

It wasn’t dating methods that her research refuted, but rather existing models of degradation, decay and fossilisation. Schweitzer and her team hypothesised that these tissues were “remnants of original proteinaceous material, highly altered by beta oxidation of original proteins to form long-chain hydrocarbon polymers”. If this was the case, then mechanisms must exist to allow their persistence across geological time. THAT had been the focus of Schweitzer’s research. [⁠5]

In 2014, she published further research showing how soft tissue structures can be preserved over millions of years, through the way which iron and oxygen chemistry “contributes to preservation in deep time, perhaps by both free-radical-mediated fixation and anti-microbial activity” [⁠6]. Because Schweitzer’s team always observed iron particles in association with these soft tissues, this is what they investigated further. Their research explained both the association of iron with many exceptionally preserved fossils, and the enhanced preservation of tissues, cells and molecules over deep time. As a result of this research, iron and oxygen chemistry are now seen to play key roles in the preservation of biomaterials after death, because it showed that iron released from some proteins becomes available for free-radical chemistry with oxygen, leading to protein and lipid cross-linking, tissue fixation, and resistance to enzymatic/bacterial degradation. There are three possibilities for this: The iron may be directly protecting proteins by blocking certain degradation activities; or, it may be providing protection indirectly by binding to oxygen, and thus preventing oxidative damage; or, it is outcompeting bacterial mechanisms that would lead to decay [⁠7]. Interestingly enough, during this research another team found similar results doing a different study, which also showed that iron influences preservation of biomolecules across geological time, further supporting the longevity of some iron-containing biomolecules⁠. [8]

Over the years, Schweitzer’s research certainly got the attention of science community, and it placed her under intense scrutiny. In her words: “There was so much interest. There was so much criticism. But I had data… I learned so much through the process. I’m so grateful. I learned how to be a careful scientist.” [9]

But if Schweitzer’s research intrigued the science community – it sent the creationist world into a frenzy, as young earth creationists sought to use her research to discredit established dating methods. Their claim is that it is simply not possible for soft-tissue to last tens of millions of years; ergo, dating methods are flawed and in doubt.

Schweitzer has repeatedly tried to refute these claims, and to explain the reasons why this is not what her research reveals. For example, in one interview she said, “One thing that does bother me, though, is that young earth creationists take my research and use it for their own message, and I think they are misleading people about it. Pastors and evangelists, who are in a position of leadership, are doubly responsible for checking facts and getting things right, but they have misquoted me and misrepresented the data”. [10]

In another article for the Smithsonian she noted that “[Christians] treat you really bad. They twist your words and they manipulate your data.” [⁠11]

What makes her patience towards young earth creationists more notable, is that she was once one herself. Again, in her own words:

“One day, shortly after I finished that program, I saw that palaeontologist Jack Horner — everyone knew him in Montana — was teaching a class on campus at Montana State. I went to class that first day of the semester and after his introductory lecture, I walked up and said, “Hi, Jack. I am a young earth creationist, and I’m going to convince you you’re wrong about evolution. Can I sit in on your class?”

He said, “I’m Jack. I’m an atheist. Have a seat.”

And instead of calling me out or making fun of my beliefs, he showed me data. No one had ever shown me data before. Often in the Christian community people aren’t talking about scientific data. Instead, Christians may hear about scientists: “They’re evil. They don’t believe in God. They’re atheists.” But many Christians haven’t heard how much data supports an ancient earth and evolution. Nobody’s told them.

Jack never tried to change my mind about anything. He just said, “Here’s the data.” And about halfway through that first semester, I began to see that my young earth views could not be supported in light of all the data. I knew God and was not willing to turn away from him. And I began to see that the two weren’t mutually exclusive as I had been taught.” [12]

The point has to be made then, that Schweitzer, having been a young earth creationist herself, fully understands both sides of the debate. If the scientist responsible for the research refutes the claims of young earth creationists – then it is her opinion we should be favouring. It’s her research after all!

Schweitzer’s research has been truly ground breaking. She upended what we knew about preservation, and then through careful research has begun to find answers to the problem. Lately, those answers have been corroborated by independent research teams who are finding similar results. So what her research has shown, is not that dating methods are shaky, but there are preservation mechanisms at work that we previously did not know about or understand. Through all this, she has remained a dedicated Christian who has been an inspirational role-model for those who have sought to find a balance between their faith in God and their love for the sciences.

1 Marcia Bosscher, The Unlikely Paleontologist: An Interview with Mary Schweitzer (Part 1) (12 Jul 2016)

2 MH Schweitzer et al, Soft-Tissue Vessels and Cellular Preservation in Tyrannosaurus rex (Science, 2015) 307(5717):1952-1955

3 TG Kaye, G Gaugler, Z Sawlowicz, Dinosaurian Soft Tissues Interpreted as Bacterial Biofilms (PLoS ONE, 2008) 3 (7): e2808. doi:10.1371/journal.pone.0002808

4 Gary Hurd, Dino Blood Redux, (TalkOrigins, 2005)

5 MH Schweitzer, J Wittmeyer, J Horner, Soft tissue and cellular preservation in vertebrate skeletal elements from the Cretaceous to the present (Proceedings of the Royal Society, 22 Jan 2007) doi:10.1098/rspb.2006.3705

6 MH Schweitzer et al, A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time (Proc. R. Soc. B., 2014) 281: 20132741.

7 MH Schweitzer et al, A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time (Proc. R. Soc. B, 2014) 281: 20132741.

8 DE Greenwalt et al, Hemoglobin-derived porphyrins preserved in a Middle Eocene blood- engorged mosquito (Proceedings of the National Academy of Sciences USA, 2014) 5. doi:10.1073/pnas.1310885110

9 Marcia Bosscher, The Unlikely Paleontologist: An Interview with Mary Schweitzer (Part 2) (13 Jul 2016)

10 Emily Ruppel, Not So Dry Bones: An interview with Mary Schweitzer (BioLogos Blog, 21 Jul 2014)

11 Helen Fields, Dinosaur Shocker (, May 2006)

12 Marcia Bosscher, The Unlikely Paleontologist: An Interview with Mary Schweitzer (Part 1) (12 Jul 2016)