How did scientists uncover soft tissue in dinosaur fossils?

­­­Fossilization is like a real-life Medusa — it petrifies living organisms. Consider petrified wood: when a tree dies and becomes buried in sediment, it is shielded by the earth, while mineral-rich water gradually permeates it. Over time, minerals replace the wood, leaving a stone replica.

Dinosaur Image Collection

The same process occurs when more complex creatures, such as animals, turn into fossils. Any part that is soft, flexible, or watery decomposes, while minerals solidify the bones, transforming them into stone. Even with rare 'mummified' fossil discoveries, preserved skin and organs are no longer soft. In such cases, the body was shielded from decay long enough for minerals to replace the soft tissues before they could decompose. Ultimately, only the stone version remains, with no trace of the original soft tissues.

At least, that's the commonly accepted view. However, in 2005, a paper published in the journal Science disputed the fundamental ideas of fossilization right from the opening line: "Soft tissues are preserved within hindlimb elements of Tyrannosaurus rex" [source: Schweitzer, 3/25/2005]. The paper describes the discovery of blood vessels, bone matrix, and elastic tissues in places where such materials should not be found.

According to traditional fossilization theories, it should be impossible to find these types of tissues preserved in a fossil. Mary Higby Schweitzer, the paper’s lead author, arrived at this unexpected conclusion by using an innovative approach to her research. Her discovery not only caused a stir in the scientific world but also carried significant implications for certain religious communities.

But how did she discover stretchy tissue within a fossilized bone, and what role do ostriches play in this? What type of analysis supports her claim that she has uncovered 65-million-year-old soft tissue? In the following sections, we will explore how Schweitzer exposed her samples and the surprising role that chance played in this groundbreaking revelation.

­

The Soft Tissue in Dinosaur Bone

In 2000, paleontologist Bob Harmon discovered a Tyrannosaurus rex specimen in the Hell Creek Formation, a fossil-rich area in eastern Montana [source: Boswell]. This particular T. rex was smaller than usual compared to other Tyrannosaurus fossils. However, once excavated and encased in plaster for transport, it became too heavy for the waiting helicopter to carry. The team had to split the fossil into two parts, accidentally breaking one of its femurs. Fragments of the femur were then sent to Dr. Mary Schweitzer at North Carolina State University.

Schweitzer took an unconventional approach with the specimen, in contrast to most paleontologists. Rather than preserving it, she deliberately destroyed it by soaking it in a weak acid. If the fossil had been entirely made of rock, the acid would have completely dissolved it. But in Schweitzer's terms, the acid demineralized the specimen. After seven days, the demineralization process exposed several unexpected tissues, including:

Much like the blood vessels in your body, those discovered by Schweitzer in the fossil were hollow, flexible, and branched. They were also transparent and contained "small round microstructures" [source: Schweitzer, 3/25/2005]. These microstructures closely resembled red blood cells, though their exact nature remains uncertain. The tissue Schweitzer uncovered was fibrous, stretchy, and resilient -- when stretched, it returned to its original shape.

Given that the widely accepted scientific theory connects dinosaurs and birds through evolution, Schweitzer and her team compared their samples to the bones of a deceased ostrich. They found the two to be quite similar. When examined under a scanning electron microscope, the dinosaur's cortical bone -- the dense, outer layer of the bone -- closely resembled that of the ostrich.

These fragments of T. rex bone led to even more surprising discoveries. In a later paper, Schweitzer and her collaborators revealed they had found medullary bone [source: Schweitzer, 6/3/2005]. Medullary bone is a type of bone found in female birds, used to store calcium for the creation of eggshells. Birds only have this bone when they are producing eggs, which suggests that the T. rex was female, pregnant, and in some ways, similar to birds.

The medullary bone was visible to the naked eye, but a further discovery made from the same sample was not. In 2007, Schweitzer and six co-authors reported that their analysis of the sample had identified the presence of collagen, a protein that is a key component of both bones and soft tissues. The team used a mass spectrometer, a device that measures the mass of atoms and particles using magnetic fields, to confirm the presence of the protein [source: Schweitzer, 1997].

By 2008, the team was extracting amino acid sequences from the sample and comparing them to those of living organisms. The results showed that the T. rex bone shared similarities with the bones of today's chickens. This research, led by Chris L. Organ, applied the same methods to a mastodon fossil and found that it was similar to modern elephants [source: Organ].

After extracting some of the fragmented amino acid chains, the team compared them to the amino acids found in modern animals. They discovered three chains that were similar to those found in chickens and two that resembled those in newts and frogs [source: Johnson].

Schweitzer and her team have since applied the same techniques to other fossils, yielding comparable results. However, her research remains controversial. Continue reading to explore both the supporters' and critics' views on her findings.

­

Young-Earth Creationism and Dinosaur Tissues

Scientists agree on one key point regarding Mary Schweitzer's research. The tissues she discovered shouldn't have been preserved, at least not according to basic theories of fossilization. Critics argue that Schweitzer actually uncovered a contaminated sample, rather than making a groundbreaking discovery. After 65 million years, there's ample opportunity for other organisms to contaminate a dinosaur's bones. Fossils can also come into contact with human and other tissues during excavation, complicating efforts to prove that a cell, tissue, or DNA strand originated from a specific extinct animal.

After Schweitzer's initial paper was published in Science, some critics argued that she released it prematurely, before completing enough analysis. Schweitzer partially agreed with this critique. She explained that the team published their findings as an early step to secure funding for more extensive research [source: Yeoman].

A rebuttal to Schweitzer's 2007 paper, which reported the presence of protein, raised several concerns, including the potential for contamination. The comment, written by Mike Buckley and several co-authors, pointed out the following issues:

In their reply to the comment, John M. Asara and Schweitzer maintained that Buckley and his co-authors had misinterpreted the data [source: Asara].

In her 2008 paper detailing protein sequences, Schweitzer bolstered the argument that the tissue found belonged to the T. rex and not some foreign contaminant. However, critics still have their doubts. For instance, researcher Christina Nielsen-Marsh, in a statement to National Geographic, declared that the sequences presented 'make no sense at all' [source: Norris]. Many remain skeptical, insisting that peptides could not have survived in a specimen as ancient as a T. rex. Consequently, they argue that the protein must have originated from another source.

In a paper published in PLoS One on July 20, 2008, researchers Thomas G. Kaye, Gary Gaugler, and Zbigniew Sawlowicz argued exactly that. After more than 200 hours of scanning electron microscope analysis of various dinosaur fossils, their team concluded that Schweitzer's samples contained framboids and that the soft tissue she identified was merely pond scum. They also employed carbon dating to determine that the material was modern, not prehistoric [source: Kaye et al.]. Schweitzer, in comments to National Geographic, maintained her position, asserting that Kaye's team had overlooked more recent protein studies of her T. rex samples [source: Roach].

However, to some, Schweitzer's discoveries make perfect sense. In the eyes of young-Earth creationists, the discovery of soft tissue provides evidence that fossils are not as ancient as scientists claim. Scientific estimates suggest T. rex fossils are 65 million years old, yet soft tissue and amino acids should only last for a fraction of that time. For someone who believes the Earth is under 10,000 years old, Schweitzer's findings may seem like convincing proof for a younger Earth, rather than a reason to reconsider the fossilization process. However, radiometric dating—the method used by scientists to date fossils—directly contradicts the notion of a 10,000-year-old Earth.

In various interviews, Schweitzer has remarked that her discoveries have enhanced rather than contradicted her Christian faith [source: Yeoman, Fields]. She has proposed several hypotheses about how the tissue could have survived for such an extended period. One theory suggests that the highly mineralized bone, along with yet-to-be-discovered geological or environmental processes, helped preserve the tissue within [source: Schweitzer, 3/25/2005]. Whether or not the broader paleontological community ultimately accepts or disputes the discovery, Schweitzer's find challenges the once-impossible and instead makes it seem improbable.