Overview
In 2003, an exceptionally well preserved T. rex leg bone was unearthed in the cretaceous rocks of Montana. Upon close examination, Dr. Mary Schweitzer found the bone to contain soft tissue inside – tiny blood vessels and proteins! Some claim that this is evidence of a young Earth, a recent extinction of the dinosaurs. Could this be, or is there another explanation?
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Contributors
Our videos benefit from guidance and advice provided by experts in science and education. This animation is the result of collaboration between the following scientists, educators, and our team of creatives.
Team
- Jon Perry
- Anthony Danzl
- Jordan Collver
- Tyler Proctor
Sources
ORIGINAL DISCOVERY OF SOFT TISSUE:
- Soft Tissue Vessels and Cellular Preservation in Tyrannosaurus rex
- Soft tissue and cellular preservation in vertebrate skeletal elements from the Cretaceous to the present
CRITIQUE OF DISCOVERY
DEFENSES OF DISCOVERY
- Influence of Microbial Biofilms on the Preservation of Primary Soft Tissue in Fossil and Extant Archosaurs
- Molecular analyses of dinosaur osteocytes support the presence of endogenous molecules
- Testing the Hypothesis of Biofilm as a Source for Soft Tissue and Cell-Like Structures Preserved in Dinosaur Bone
- 10 million year old frog bones with marrow preserved
IRON’S ROLE IN PRESERVATION
OTHER DINOSAURS WITH SOFT TISSUE DISCOVERED
- Mass Spectrometry and Antibody-Based Characterization of Blood Vessels from Brachylophosaurus canadensis
- Evidence of preserved collagen in an Early Jurassic sauropodomorph dinosaur revealed by synchrotron FTIR microspectroscopy
- Soft sheets of fibrillar bone from a fossil of the supraorbital horn of the dinosaur Triceratops horridus
- Hemoglobin-derived porphyrins preserved in a Middle Eocene blood-engorged mosquito
- Molecular preservation in Late Cretaceous sauropod dinosaur eggshells
Corrections
Since writing the script for this video, a new study came out that weakens the consensus that the tissue found belongs to the original T. rex.
Transcript
Soft tissue has been found in T. rex bones! What could this mean?
In 2003, a team of paleontologists finished excavating an incomplete yet exceptionally well preserved T. rex skeleton. During removal, the animal’s thigh bone was broken in half. Before it was repaired, Dr Mary Schweitzer requested a piece of the bone for destructive dissection and chemical analysis.
After applying a solvent designed to remove hard minerals, a diverse collection of soft material could be seen under the microscope. It included what looked like tiny blood vessels (those commonly found inside fresh bone) several types of protein, and even the remnants of what looked like individual red blood cells.
She was shocked. According to our understanding at the time, unless tanned like leather with special chemicals, soft tissue was predicted to completely deteriorate, even under the best of circumstances, in less than 1 million years. This T. rex leg bone, however, was found in rocks dating back 68 million years. What could this discovery of soft tissue mean?
To Dr Schweitzer (and most other researchers) it could only mean one of three things:
1. The fossil might be far younger than previously thought, possibly less than 1 million years old.
2. The fossil may have been recently contaminated by microbes that produced the soft structures after the bone had fossilized. A substance known as “biofilm”.
3. There may be a previously unknown natural mechanism capable of preserving soft tissue far longer than 1 million years.
Having studied paleontology throughout her career, Dr. Schweitzer knew that option number 1 was least likely. Thousands of observable data points have been collected by many independent researchers over the years. All of these observations point to an ancient extinction of the dinosaurs. In the case of T. rex, the last of their kind went extinct over 65 million years ago. To successfully argue that her single discovery means T. rex actually went extinct recently, she would have to show why all of the other facts we’ve discovered about their extinction are wrong. At least for now, she scratched this option off her list.
At first, other researchers in the field figured option number 2 was most likely. As is the custom in science, they published articles critiquing her work. They showed how bacteria and fungi can invade a fossil and produce Biofilms very similar to what she had found. However, after closer examination, several years of debate, and many papers published back and forth, the scientific community is now largely convinced – the soft tissue Dr. Schweitzer had found, did come from a dinosaur.
This left serious thinkers convinced that option number #3 was most likely, but how? What natural process or collection of natural processes, could allow soft tissue to remain intact for over 68 million years? No one had an answer but Dr. Schweitzer was determined to figure it out.
Years went by without any leads until one day, during a random lecture she attended on brain disease, Dr Schweitzer learned about the destructive power of iron particles on living brain tissue.
Iron particles are common in our blood. Normally, however, they’re trapped safely inside hemoglobin, a blood protein that uses iron to capture oxygen in the lungs, and deliver it throughout the body.
While iron is safe and highly useful inside hemoglobin, loose iron particles can wreak havoc on our cells. In a process called cross-linking, iron can trigger a series of reactions eventually causing proteins and other cellular structures to unravel and fuse together in a tangled useless mess.
In a living brain, cross-linking can cause dementia, but Mary Schweitzer immediately realized that in dead tissue, cross-linking causes preservation.
She had long known that leather is produced by applying chemicals to hides that cross-link their proteins. Cross-linked proteins are extremely durable and bacteria can no longer eat them.
Having this epiphany, Dr. Schweitzer immediately re-examined her specimens. Jackpot! Each sample was loaded with iron particles.
She imagined a scenario like this: When a large animal dies and blood begins to decompose, iron is released from hemoglobin. As it seeps out into tissues and bone in high concentration, it initiates cross-linking.
Soft tissues most affected are preserved like leather. Tissues that are both cross-linked and protected safely inside hard bone might even survive for millions of years.
The story seemed reasonable, but Dr. Mary Schweitzer is a scientist. Arm-chair philosophy was not good enough for her.
To test her hypothesis in the real world, she got hold of blood vessels from an ostrich (similar in size to the vessels found in the fossil). At room temperature, one batch of blood vessels was placed in normal water to see how long it took to decompose. Another batch was placed in a bath of iron rich blood cells.
The vessels in water turned to mush in just 3 days. After two years, those soaked in iron rich blood cells were still completely intact, no signs of degradation could be found. The experiment continues today, 6 years and counting. The results are still the same.
6 years, of course, is a far cry from 68 million. While projections suggest the process could work for millions of years, we still don’t know for sure if iron alone is enough. That said, her experiment is a wonderful start and her story is a beautiful example of how good science works.
Dr. Schweitzer began by making an observation; presented that observation to scientists for their scrutiny and critique, giving them all the information they needed to check her work; she came up with an explanation or hypothesis for the observation; and finally, using her creativity, she designed an experiment to test that hypothesis, publishing her results and methods for others to try, examine, and critique as well.
Her discovery has inspired others to look for soft tissue a variety of fossils. It has now been found in many dinosaur specimens. Some researchers, including Dr. Schweitzer, have even found what looks like ancient fragments of DNA.
While we don’t expect to find entire dino genes that are still readable, who knows what the future may hold.
I’m Jon Perry, that is the significance of soft tissue found in dinosaur bones, Stated Clearly.