Soft Tissue in Dinosaur Fossils: Evidence for a Young Earth?
In an earlier article, “Evidences for a Young Earth”, I discussed a number of proposed physical evidences that the earth is only a few thousand years old, rather than billions of years old. Holding to a literal interpretation of Genesis, young earth creationists circulate about a hundred of these arguments for a young earth. Most of these claims have been around for several decades, and have long since been addressed by mainstream scientists.
A relatively new area of controversy is the discovery of soft tissues in dinosaur fossils. The state of these discoveries changes every few years, so some of the standard science web sites have not kept up. This is a somewhat dramatic topic, which the young earth proponents have appropriated enthusiastically. It is #3 on a list of “10 Best Evidences From Science That Confirm a Young Earth”, according to Answers in Genesis.
A 2009 Institute for Creation Research article by B. Thomas  leads off:
In recent decades, soft, squishy tissues have been discovered inside fossilized dinosaur bones. They seem so fresh that it appears as though the bodies were buried only a few thousand years ago.
Since many think of a fossil as having had the original bone material replaced by minerals, the presence of actual bone–let alone pliable blood vessels, red blood cells, and proteins inside the bone–is quite extraordinary. These finds also present a dilemma. Given the fact that organic materials like blood vessels and blood cells rot, and the rates at which certain proteins decay, how could these soft tissues have been preserved for ten thousand, let alone 65 million or more, years?
This sounds amazing – – “fresh”, “soft, squishy tissues” and “pliable blood vessels, red blood cells, and proteins”. This verbiage makes the reader think that someone cracked open these dinosaur bones and found raw tissue flopping around inside, dripping with red blood cells. Is that really the case? Let’s turn to the facts. Here are the topics treated below:
1992: Mary Schweitzer Sees What Looks Like Red Blood Cells
2004: Schweitzer Finds Bits of Soft Tissue in T. Rex Bones
2006 Onward: Sequencing Proteins from Dinosaur Bones
Mechanisms for Ancient Protein Preservation
Osteocyte Cells, Traces of DNA, and Iron as a Preservative
Assessment of Evidence That Soft Tissue Can Persist for 70 Million Years
Invariance of Radioactive Decay Rates
The Dinosaur-Bird Connection
Mary Schweitzer on Creation
1992: Mary Schweitzer Sees What Looks Like Red Blood Cells
Key discoveries in this area over the past twenty years have been made by Mary Schweitzer, now a professor of paleontology at North Carolina State University. In 2010, she wrote an article, “Blood From Stone”, in Scientific American which summarized her work to that point . She starts off describing an afternoon in 1992, when she was a graduate student looking in a microscope at a thin bone slice from a newly excavated Tyrannosaurus rex fossil skeleton. She saw what looked like red blood cells – they were “the right size, shape and color to be blood cells, and they were in the right place, too.” This was a surprise, since “The conventional wisdom holds that when an animal dies under conditions suitable for fossilization, inert minerals from the surrounding environment eventually replace all of the organic molecules—such as those that make up cells, tissues, pigments and proteins—leaving behind bones composed entirely of mineral.”
Were these actually red blood cells, or the chemically transformed remains of red blood cells, or merely artifacts of some unknown geological process that produced rounded blobs of material? If these objects were red blood cells, how could organic matter be preserved for more than 65 million years, when the last of the dinosaurs died out? Schweitzer has spent the last two decades trying to answer these questions.
In the mid-1990’s she did a couple of chemical tests with the dinosaur bones. Spectroscopic tests of light wavelengths emitted or absorbed indicated that somewhere in the fossil bones were compounds that were consistent with heme. Heme is a small, relatively stable iron-containing molecule which gives blood its red color and is the key oxygen-carrying component of the hemoglobin protein. Heme has been identified by Greenwalt, et al. in the abdomen of a 46-million-year-old mosquito fossil. Schweitzer noted in a 1997 article :
We also thought hemoglobin could be in the tissue because at its core are structures that have a reputation for durability. Called heme units, these chemically stable structures consist of a ringlike organic compound called porphyrin bound to an iron atom. Porphyrins are an important part of many biological molecules, including chlorophyll, which plants need for photosynthesis. Porphyrins derived from chlorophyll have been found in sediments dating back to the Carboniferous, when vast forests blanketed the planet many millions of years before the dinosaurs existed. So we did not think it too far-fetched that heme units from hemoglobin might still exist in our T. rex.
Also, the responses of immune systems of laboratory mice to injections of powdered dinosaur bones suggested that the bones “contained something similar to the hemoglobin in living animals”. The observed immune response did not require that a full hemoglobin protein was present in the fossil bones, but only a tiny fragment of the protein, “possibly 3-4 amino acids”.
At that point, Schweitzer recounts , “We could not show that the hemoglobinlike substance was specific to the red structures—the available techniques were not sufficiently sensitive to permit such differentiation. Thus, we could not claim definitively that they were blood cells. When we published our findings in 1997, we drew our conclusions conservatively, stating that hemoglobin proteins might be preserved and that the most likely source of such proteins was the cells of the dinosaur. The paper got very little notice.”
Just to be clear, her assessment of these objects was that they were not actual red blood cells (e.g. with cell walls or other cellular structures), but rather some chemically transformed remnants of the dinosaur blood :
Clearly these structures are not functional cells. However, one possibility is that they represent diagenetic alteration of original blood remnants, such as complexes of hemoglobin breakdown products, a possibility supported by other data that demonstrate that organic components remain in these dinosaur tissues.
In the next few years, she analyzed some other fossils from the age of dinosaurs, finding evidence for preservation of some keratin proteins from fossil claws and from feather-like fibers. She noted  that keratin proteins “are good candidates for preservation because they are abundant in vertebrates, and the composition of this protein family makes them very resistant to degradation.” This work was published in 1999. Again, it was largely ignored, since her findings “challenged everything scientists thought they knew about the breakdown of cells and molecules. Test-tube studies of organic molecules indicated that proteins should not persist more than a million years or so.”
Fuelling the skepticism of her colleagues at that time was the recent debunking of some 1990’s claims of the finding of DNA in dinosaur fossils. In one case, the DNA was found to have resulted from human contamination, and in the other case the DNA came from living fungi and plants, not a reptile .
2004: Schweitzer Finds Bits of Soft Tissue in T. Rex Bones
In 2003, Schweitzer received some chunks of T. rex thigh bone (femur), from a recently-excavated fossil skeleton from base of the Hell Creek formation in Montana. This formation has been dated by various radiometric means to about 65-68 million years ago.
In today’s birds, when a female bird is about to lay eggs, it produces distinctive “medullary” bone which serves as a reservoir of calcium for the egg-shells. Schweitzer noticed that the dinosaur thigh bone specimen seemed to include some of this type of bone. For bird bones, one can dissolve the hard mineral part of the bone away in weak acid over a period of weeks, leaving the soft tissue available for examination. In early 2004, Schweitzer asked her technician to treat the T. rex bones in this manner. For the medullary bone they found that this treatment yielded the stretchy, fibrous tissue shown below:When the regular cortical bone was likewise dissolved away with weak acid, a network of what looked like normal, flexible blood vessels was revealed: Inside the vessels were suspended what looked like red blood cells: 2006 Onward: Sequencing Proteins from Dinosaur Bones
Schweitzer and her colleagues published these photos in the prestigious journal Science in 2005 . She recounts :
The paper garnered a lot of attention, but the scientific community adopted a wait-and-see attitude. We claimed only that the material we found resembled these modern components— not that they were one and the same. After millions of years, buried in sediments and exposed to geochemical conditions that varied over time, what was preserved in these bones might bear little chemical resemblance to what was there when the dinosaur was alive. The real value of these materials could be determined only if their composition could be discerned. Our work had just begun.
Using all the techniques honed while studying [other fossils], I began an in-depth analysis of this T. rex’s bone in collaboration with Asara, who had refined the purification and sequencing methods we used in the mammoth study and was ready to try sequencing the dinosaur’s much older proteins. This was a much harder exercise, because the concentration of organics in the dinosaur was orders of magnitude less than in the much younger mammoth and because the proteins were very degraded. Nevertheless, we were eventually able to sequence them. And, gratifyingly, when our colleague Chris Organ of Harvard compared the T. rex sequences with those of a multitude of other organisms, he found that they grouped most closely with birds, followed by crocodiles— the two groups that are the closest living relatives of dinosaurs.
When the papers detailing this protein sequencing work were published in 2007 [7, 8] and 2008, they generated “a firestorm of controversy”. Because proteins in laboratory experiments degrade relatively quickly, it was believed in the scientific community that original proteins simply could not persist for so many millions of years. Some scientists viciously attacked the protein sequencing techniques of Schweitzer’s collaborator, John Asara of Harvard Medical School .
Also, Thomas Kaye, et al. published a paper in 2008  which made a strong case that the flexible stuff found in dinosaur bones was merely a “biofilm” produced by modern bacteria which had invaded the bone pores. Kaye’s team used electron microscopy to examine material from a range of fossils, including some from the same Hell Creek formation which had produced Schweitzer’s T. rex. Doing the same sort of demineralization as Schweitzer, Kaye found similar structures, but interpreted them differently. The photo below shows branching vessels, containing small round red objects, which are about the same size as red blood cells. These objects were identified as “framboids”, which are a small, round deposits of inorganic iron mineral. Framboids are common in various sediments, and typically have nothing to do with red blood cells or other biological origin. Presumably they formed in these pores in the fossil bones by inorganic geochemical processes.
Kaye, et al.  found that the infrared spectrum from organic material scraped from chambers in a fossil turtle shell (carapace) recovered from the Hell Creek formation better matched a modern bacterial biofilm than collagen protein from a modern chicken tendon. This supported their contention that the soft tissue in the fossils was bacterial in origin, not preserved reptilian tissue. Also, when they submitted some of the soft tissue extracted from fossil bones for carbon-14 dating, the results showed a modern date, again pointing to recent bacterial activity as the origin of these materials.
My opinions, which are subject to correction, on Kaye’s biofilm results  are:
( a ) From looking at the electronic micrographs, his identification of the little round red things as spheres of primarily inorganic iron oxide is correct. While they are clearly not red blood cells, the iron may have originated from the dinosaur hemoglobin.
( b) The soft stuff he scraped from the fossil turtle carapace might well be bacterial slime, as he proposed, based on the infrared signature. His paper notes, “A turtle carapace from the Hell Creek formation was selected for spectroscopy because of its proportionally large chambers in the trabecular bone that allowed scraping the coatings loose.” The “large chambers” might have served as accessible habitat for soil bacteria. This environment would differ from the hermetically-sealed, largely mineralized interior pores of dinosaur bones.
( c ) His carbon-14 results, giving post-1950 age to his organic matter, are not consistent with either a 70-million-year-old origin or a 4500-year-old Noahic Flood burial. It is possible that the interior of his particular bone sample was infiltrated by bacteria, or by humic or other inorganic soil acids.
For some months, Kaye’s biofilm thesis seemed more credible to the scientific community than Schweitzer’s contention that the soft tissues were the remnants of actual dinosaur tissue. Schweitzer’s team responded with an in-depth analysis of bones from an 80-million-year-old duckbill hadrosaur, B. canadensis . These fossil bones were exhumed relatively quickly and rushed to the lab for analysis, to minimize exposure to the elements. Her team found the tissues in this second dinosaur were better-preserved than the earlier T. rex. The morphology of these tissues, their immunological behavior, and the sequences of amino acids in fragments of protein were consistent with them being derived from animal (dinosaur) tissue, not from bacteria. Schweitzer writes :
As we had hoped, we found cells embedded in a matrix of white collagen fibers in the animal’s bone. The cells exhibited long, thin, branchlike extensions that are characteristic of osteocytes, which we could trace from the cell body to where they connected to other cells. A few of them even contained what appeared to be internal structures, including possible nuclei.
Furthermore, extracts of the duckbill’s bone reacted with antibodies that target collagen and other proteins that bacteria do not manufacture, refuting the suggestion that our soft-tissue structures were merely biofilms. In addition, the protein sequences we obtained from the bone most closely resembled those of modern birds, just as [the earlier T. rex’s] did. And we sent samples of the duckbill’s bone to several different labs for independent testing, all of which confirmed our results.
The high-resolution protein sequences from this duckbill dinosaur showed it to be more closely related to living birds than to living alligators . This is consistent with evolutionary expectations from the fossil record. Statistical analyses of collagen protein gave a “robust” grouping of the two dinosaurs (the duckbill hadrosaur and the earlier T. rex protein sequences) with birds (ostrich and chicken), but there was not enough sequence data to correctly parse out the relationships among the two dinosaurs and the two birds.
The analyses showed evidence for crosslinking of the proteins, and other chemical modifications (e.g., “unusual complexes between C, N, and Fe”) that are consistent with long-term aging and stabilization of this material. Schweitzer noted  that these findings evidently swayed scientific opinion in her direction: “After we reported these findings in Science in 2009, I heard no complaints.”
Mechanisms for Ancient Protein Preservation
Schweitzer has shifted focus in recent years from simply demonstrating that fragments of protein did survive for millions of years in dinosaur bones, to considering the mechanisms of how this protein was preserved. In a 2005 article  she acknowledged that, “Evidence supporting the preservation of endogenous biomolecules in the pre-Cenozoic fossil record has generally been met with skepticism, because it is assumed that primary organic molecules cannot withstand the alterations and breakdown that occur during diagenesis.” However, this skeptical opinion was based on test-tube experiments which may not adequately represent the conditions within the pores of dinosaur bone: “Laboratory experiments designed to approximate molecular diagenesis apply physical and chemical parameters not normally encountered in nature (e.g. pH <1, T >300 ⁰C) and do not account for the protective effects of mineral association. Therefore, their utility as a proxy for diagenetic processes at the molecular level in naturally preserved samples is somewhat limited.” Schweitzer went on to list some 16 earlier studies which showed that “ amino acids, short peptides, and amino sugars can persist within fossils over a wide geological age distribution”, plus 14 studies where “immunological techniques have identified antigenic compounds in fossils of varying ages and from various source taxa.”
Schweitzer published a broad review  of “Soft Tissue Preservation in Terrestrial Mesozoic Vertebrates” in 2011. Citing more than 200 studies, she discussed many prior instances of soft tissue finds among Mesozoic fossils. The Mesozoic era is seen as ranging from about 252 to 66 million years ago, and has been termed the “Age of Reptiles”, since they were dominant animals on land, in the air, and in the sea. Most examples of tissue preservation are of the skin and its appendages, including scales, feathers, and claws. These “consist largely of durable and waterproof keratin proteins”. Keratin has high preservation potential “because of its molecular structure, its tendency to form cross-links, and its abundant, nonpolar amino acids.”
However, even these finds are unusual, since the norm is for skin as well as underlying tissue to completely decompose:
Because the carbon and nitrogen that make up proteins, DNA, cells, and tissues of multicellular organisms are useful to microbes for metabolic energy, organic remains are normally degraded rapidly postmortem; indeed, under normal circumstances, more than 99% of the reduced carbon making up these components is returned quickly to the carbon cycle by microbes. Taphonomic experiments show that in most cases where whole carcasses of been deposited on the ground surface, they can be completely skeletonized in as little as 2 to 3 weeks, and degradation-linked changes in cell morphology/chemistry can occur within minutes of death. Consequently, the presence of originally soft tissue components or cells in association with fossilized remains of extinct organisms shows that processes normally involved in degradation have been slowed or arrested soon after death, and before complete decay occurs.
Schweitzer offers some suggestions for how this mitigation of decay may come about. If an animal carcass dries out fairly rapidly, its tissues can undergo changes which render them more stable: “…early desiccation through mummification may make these specimens prime targets for the recovery of biomolecules other than collagen.”
As an aside, many of the eye-catching headlines about “mummified dinosaurs” are misleading. For instance, a 2007 National Geographic article was captioned, ” ‘Dinosaur Mummy’ Found; Has Intact Skin, Tissue “. What you only discover half-way through the article is that the skin and other tissue have been replaced by minerals, so this is not the preservation of organic soft tissue, but rather the preservation of the detailed physical forms of the original soft tissues. This is interesting, but it is also reasonably well-understood, at least in outline. Lingham-Soliara and Glabb  reported on their analysis of the microstructure of collagen from decomposed dolphin, python and turtle tissue, which had subsequently been air-dried. They found that, despite this severe exposure to decay and dehydration, “many collagen fibres maintained their structural integrity, showing little degradation”. Also, “re-hydrating the dehydrated tissue showed minimal structural loss”. They concluded that a viable path for the preservation of soft tissue long enough for it to become mineralized (fossilized) would be for an animal to die during a dry spell (which presumably also killed off most scavengers), become mummified, and later get covered with mineral-rich water or sediments.
Schweitzer  also mentioned earlier studies which discussed the stabilization of tissues within mineral settings like the pores of bone:
Close association with the mineral phase (Child 1995) may act similarly to chemical fixation (e.g., with formaldehyde), offsetting enzymatic and microbial degradation (Kharalkar et al. 2009 and references therein). This may occur because microbial enzymes are too large for most pores in bone and because the mineral phase of bone forms a barrier to digestion (Trueman & Martill 2002, Turner-Walker 2008). Alternatively it may occur because the small size, large surface area, and reactivity of bone mineral crystals may inhibit enzymatic degradation, in a process similar to that demonstrated for clay grains (Butterfield 1990, 2003). Finally, the constraints of association with mineral may prevent molecular swelling during degradation, ultimately preventing access to more reactive sites on molecules (M. J. Collins, personal communication).
A 2011 study by San Antonio, Schweitzer and others  involved the analysis of fragments (peptides) of collagen protein recovered from dinosaur bones, and mapping the results onto molecular models of collagen derived from existing species to determine the configuration of the collagen molecules within the dinosaur bones. The abstract reads, in part:
The dinosaur peptides localized to fibril regions protected by the close packing of collagen molecules, and contained few acidic amino acids. Four peptides mapped to collagen regions crucial for cell-collagen interactions and tissue development. Dinosaur peptides were not represented in more exposed parts of the collagen fibril or regions mediating intermolecular cross-linking. Thus functionally significant regions of collagen fibrils that are physically shielded within the fibril may be preferentially preserved in fossils.
These results show empirically that structure-function relationships at the molecular level could contribute to selective preservation in fossilized vertebrate remains across geological time, suggest a ‘preservation motif’, and bolster current concepts linking collagen structure to biological function. This non-random distribution supports the hypothesis that the peptides are produced by the extinct organisms and suggests a chemical mechanism for survival.
San Antonio, et al.  note that extrapolations of glassware studies of protein degradation at accelerated conditions of acidity and high temperature predict that protein strands cannot last more than a few million years (at 10 ⁰C), but suggest that these models may not be appropriate, since “they do not consider the molecules in their native state (i.e., folded, closely-packed, cross-linked or, in the case of bone, stabilized by association with the mineral phase).”
Demarchi, et al.  have recently quantified and mechanistically described the stabilization of proteins which are bound to a mineral surface. They found that this surface effect accounts for the survival of original proteins in fossil ostrich eggs in hot climates for millions of years, which is far longer than expected.
Fazale Rana of Reasons to Believe (an evangelical Christian ministry which accepts an old earth) unpacked the significance of these findings  :
Collagen’s basic structural unit is called a triple helix, consisting of three protein chains intertwining around each other. At certain points along the triple helix, the individual protein strands are chemically bound to each other to form crosslinks.
Numerous collagen triple helices assemble in a staggered fashion to form a larger structure called a collagen fibril. Large numbers of collagen fibrils in turn assemble, with the aid of other proteins, into collagen fibers.
The highly intertwined, cross-linked structure of collagen makes it reasonable that fragments of this molecule could survive for 68 million years. Even if the individual protein strands break down, the fiber would still remain largely intact because of all the association points. Once the protein strand breaks, the fragments are held in close proximity by the contact points. This forced closeness allows for broken strands to occasionally rejoin and reform the original protein. If the broken strands were not held juxtaposed to each other, the fragments would diffuse away from each other, thus, preventing the reversal of the degradation process.
Finally, collagen’s association with the bone matrix provides added stability to the collagen proteins. Within the bone matrix, collagen fibers adsorb to the mineral component of bone. The contact with the surface protects the protein and keeps the pieces of collagen juxtaposed whenever the protein strands break.
In 2016 Rana, a biochemist by profession, published Dinosaur Blood and the Age of the Earth, a short book dedicated to the questions around dinosaur soft tissue. After describing finds of soft tissue in dinosaur and other ancient fossils, he explains why they do not mean the earth is young. He debunks the young earth creationist claims that radiogenic dating of rocks is unreliable, and describes nine conditions or mechanisms which can work together to help preserve protein remnants in dinosaur bones.
After death, cell-destroying enzymes can be let loose in the body, accelerating decay. However, in a 2002 review of the survival of organic matter in bone, Collins et al.  affirmed that “the collagen in bone is protected by the physical exclusion of microbial extracellular enzymes.” According to Peterson et al. , after microbes invade the outermost pores of dinosaur bones, their metabolic activities lead to mineral deposits which hermetically seal off the innermost zones of the bones from further attack by microbes.
Osteocyte Cells, Traces of DNA, and Iron as a Preservative
A 2013 article in Bone by Schweitzer, et al.  covered a number of topics. Whereas her earlier studies had dealt mainly on characterizing collagen-based structures in dinosaur bones, here she focused on what appeared to be the remnants of osteocyte cells. Osteocytes are the most common type of cell found within bone. They help to regulate the mineralization chemistry of the bone, to maintain proper bone mass. To obtain the osteocyte remains, she first removed the mineral portion of bones from two dinosaurs using weak acid solutions, as described earlier. Then, to free the osteocytes from their collagen matrix, she used an enzyme that decomposes collagen. The recovered osteocytes were reddish, due to a high iron content, and physically resembled osteocytes extracted from extant birds.
Schweitzer, et al.  used antibodies that bind to specific proteins to demonstrate the presence of four proteins expected to be in osteocytes, namely actin, tubulin, PHEX, and histone H4. The patterns of the binding of these antibodies within the dinosaur osteocytes matched the patterns seen for binding to osteocytes extracted from ostrich. The antibodies did not bind to surrounding matrix tissue or to associated sediments. Mass spectrometry also found amino acid sequences consistent with these four proteins. Actin, tubulin, and histone H4 are not found in bacteria, so this is further evidence against the biofilm explanation of these soft tissues.
A particular PHEX antibody, called OB 7.3, was used here. Among extant taxa tested, it binds only for birds. It was shown in this study to bind strongly to the dinosaur and ostrich osteocytes, but not at all to alligator osteocyte.
Histone proteins, such as the H4 found in the dinosaur bones, are associated with DNA. The presence of fragments of actual DNA in the dinosaur osteocytes is suggested by the binding of an antibody for the DNA backbone, and the binding of two chemical stains known as PI and DAPI. The staining for the dinosaur cells showed similar spatial patterns as the stains in ostrich osteocytes, supporting the view that this DNA is from the original dinosaur cells, rather than from microbial infiltration. These stains can bind to DNA strands as short as 4 to 20 base pairs, so these results do not require that long sequences have been preserved. Only about 15-20% of the dinosaur cells showed any response to staining, and for those that did react, the staining was much less intense than for the ostrich. Thus, any DNA remnants in the dinosaur bones are quite degraded. Schweitzer’s team could only detect bare traces of DNA, not nearly enough to do sequencing so as to verify that this is actually dinosaur DNA: “These data are not sufficient to support the claim that DNA visualized in these cells is dinosaurian in origin.”
In a 2016 interview , Schweitzer noted:
“I’ve found DNA in dinosaur bone,” said Mary Schweitzer, a molecular paleontologist at North Carolina State University. “But we did not sequence it — we couldn’t recover it, [and] we couldn’t characterize it. Whoever it belongs to is a mystery.”
It’s no surprise that dinosaur remains contain DNA, she said. Bone is partly made up of a mineral called hydroxyapatite, which has a strong affinity for certain biomolecules, including DNA. In fact, researchers often use hydroxyapatite to purify and concentrate DNA in the lab, Schweitzer said.
“That’s one of the reasons that I don’t work with DNA myself,” Schweitzer told Live Science. “It is too prone to contamination and really difficult to interpret.”
The poor showing for DNA in dinosaur fossils is a strike against young earth creationism: if the dinosaurs were buried in a great flood only 4500 years ago, we should be finding gobs of DNA with nice long sequences in at least some of the dinosaur remains in our possession. It is now common to sequence DNA from certain other fossil finds, but not from dinosaurs.
In 2012 Allentoft, et al.  published a study of the DNA preserved in bones from specimens of moa bird that were excavated in New Zealand from anoxic, limestone-buffered sediments . The moa was a large flightless bird that was the dominant herbivore in New Zealand before the Maori arrived and hunted them to extinction. In this study, the left leg bones from 158 moa skeletons were dated by radiocarbon, and assessed for DNA content. The dates for these skeletons ranged from 602 to 7839 years before present, with all but one specimen being younger than about 5800 years. The authors proposed an exponential fit to the data, with a half-life of 521 years for mitochondrial DNA. This model predicts that DNA would completely degrade to a single base pair in 131,000 years at 15 ⁰C (59 ⁰F), in 882,000 years at 5 ⁰C (41 ⁰F), and in 6,830,000 years at a glacial temperature of -5 ⁰C (23 ⁰F).
This would seem to preclude the survival of any DNA fragments in the ~ 68 million-year-old dinosaur bones in the Schweitzer, et al.  study. However, the data in the Allentoft, et al.  study were highly scattered; only 38.6% of the variation in DNA degradation between moa-bone samples was accounted for by age differences. For the set of results which all date to about 2700 years ago, the DNA amounts vary from about 0.002 to 100. That is a factor of 50,000 difference from least to most, showing the enormous variability of results just within this relatively small, homogeneous data set.
This indicates that the rate of DNA decay can vary widely from sample to sample due to various environmental factors. For instance, the DNA degradation rates in the moa bones were found to be nearly 400 times slower than predicted from published kinetic data of in vitro DNA decomposition. Thus, it is not clear that these relative short-term (less than 8000 years old) results with bird bones in a limestone setting necessarily predict the fate of DNA in other specimens, such as the much larger dinosaur bones which were deposited in sandstone. As another example of the longevity of DNA under some conditions, fragments of mitochondrial DNA, long enough to sequence, have recently been recovered from a 400,000 year old hominin fossil .
Schweitzer, et al.  proposed a number of molecular mechanisms for long-term preservation of cells and some of their chemical components within dinosaur bones. These factors include isolation within tiny pores in the bone, association with the bone mineral, the tertiary structures of the proteins, and the role of iron in promoting cross-linking. I’ll quote that whole section of that paper, as usual omitting the literature references:
Cells are usually completely degraded soon after the death of the organism, so how could ‘cells’ and the molecules that comprise them persist in Mesozoic bone? In the mineralized matrix of bone, many factors converge to alter the dynamics of cell death and degradation, ultimately contributing to disruption of the degradation pathway. For example, necrotic or apoptotic cells are rapidly destroyed by phagocytosis or by microbial attack post-mortem, but osteocytes are inaccessible to other live cells, which may, in part, explain their preservation in these ancient tissues. Second, osteocytes are inherently resistant to degradation because location within the bone matrix inhibits cell division, therefore cells may be required to last the lifetime of the organism. Osteocyte expression of apoptotic repressor proteins may also contribute to their persistence. The association of actin with alpha-actinin and fimbrin confers stability to actin over the lifetime of the cell and may also stabilize the protein after death. Finally, osteocytes have limited access to oxygen within the bone matrix, and may thus be protected from oxidative damage.
Cell death, whether by apoptosis or necrosis, is quickly followed by autolysis, which normally destroys the cell and releases autolytic enzymes into the surrounding environment. Autolysis, however, is self-limiting, and after reaching a certain threshold, the remaining cells are stable for long periods.
The association with mineral affords other protections that are unavailable to non-biomineralized tissues and cells. The microcrystalline surfaces of apatite may act like clay grains, adsorbing degradative
enzymes and inactivating them, and in addition to limiting access of microbes to osteocytes, the rigid bone matrix may also inhibit denaturation and molecular swelling that precedes autolysis.
In 2007, we hypothesized that iron, released post-mortem from hemoglobin and myoglobin through autolysis/degradation of red blood cells and muscle tissue, would act to “fix” both tissues and molecules, a hypothesis also put forth by others Biologically active Fe (II), which is soluble, would rapidly convert to Fe (III) upon release from the cell, and precipitate out of solution. Iron is a reactive oxygen species (ROS), and this switch triggers the formation of hydroxyl radicals Through a cascade of events referred to as Fenton chemistry highly reactive hydroxyl radicals trigger both crosslinking of proteins and peroxidation and crosslinking of the fatty acids making up cell membranes Because osteocytes are intimately linked through filopodia to the vascular system of bone and because the iron-binding protein ferritin has been identified in this cell line they would be susceptible to this chain reaction.
Iron is implicated in the preservation of these transparent microstructures by its intimate association with the cell “membranes” in analytical TEM (Fig. S1), and further supported by the increase in antibody response in all cases in which these dinosaur ‘cells’ have been treated with the iron chelator PIH (see Extended Experimental Methods in Appendix A). If the membranes of these ‘cells’ were preserved through iron-mediated crosslinking (Fig S1), it also provides a mechanism whereby membrane associated proteins may be preserved. Actin and tubulin have a tertiary structure that make them inherently resistant to early degradation but their close association with a naturally ‘fixed’ membrane would increase their preservation potential greatly. Similarly, PHEX is a transmembrane protein, and those regions of the protein embedded within the membrane would be naturally ‘fixed’ along with the membrane. Iron may also function to bind oxygen, preventing oxidative damage to tissues and molecules. Finally, once the ‘cells’ are fixed in this manner, they may be further stabilized by mobilization and template mediated precipitation of microcrystalline apatite in early diagenesis.
In another 2013 study, Schweitzer, et al.  experimentally probed the role of iron in preserving proteins. After an animal dies, the iron from the hemoglobin in their red blood cells can be released to interact with other tissues. They cite prior publications which describe how iron can facilitate the formation of oxy radicals, which “facilitate protein cross-linking in a manner analogous to the actions of tissue fixatives (e.g. formaldehyde), thus increasing resistance of these ‘fixed’ biomolecules to enzymatic or microbial digestion”. Using an array of analytical techniques, they observed iron-rich nanoparticles as being intimately associated with the preserved flexible vessel tissue recovered from the bones of T. rex and duckbill dinosaurs. The high-magnification image below shows inorganic iron-rich nanoparticles associated with the organic layer of the vessel of a T. rex. In this image the iron particles appear to be concentrated on the outside of the vessel. The duckbill vessel tissue (see Figure 1(b) of Schweitzer, et al. ) is more uniformly infiltrated throughout by iron particles. It seems likely to me that the iron was originally more finely dispersed and more available to do chemistry, and later precipitated into these nanoparticles.
Direct contact with iron or iron particles, as with direct contact with bone mineral, can assist in tissue stabilization. In these images, internal cellular features like chromatin and nuclear membrane were visible in ostrich tissue, but not in the dinosaur structures, which is consistent with substantial degradation of the internals of the dinosaur cells.When iron was chemically removed from the vessels by treatment with chelating agents, the response of the vessel tissues to specific protein antibodies increased dramatically. This is another indication of the association of residual iron with these preserved proteins.
Schweitzer, et al.  also incubated blood vessels from ostriches in a variety of solutions to test the effect of hemoglobin-derived iron on tissue preservation. Some ostrich vessels were incubated in a solution of hemoglobin. This hemoglobin had been extracted from the red blood cells of chicken and ostrich blood, and then re-diluted to its original concentration in the avian blood. The vessels sitting in hemoglobin solution have shown no signs of degradation for more than two years. In contrast, the ostrich vessels in plain water or phosphate buffered saline (PBS) showed significant degradation within three days, i.e. more than 240 times faster degradation than with the hemoglobin. These results dramatically demonstrate the efficacy of iron-based tissue preservation, which has not generally been taken into account in earlier estimates of how long proteins can survive.
A 2014 study by Boatman, et al.  involved further experiments to investigate iron-based effect on proteins. Initial infrared spectroscopy suggested the presence of highly crosslinked collagen within dinosaur fossil tissue. The researchers identified two likely non-enzymatic crosslinking mechanisms, Fenton’s reaction and glycation. Both of these reactions depend on the oxidation potential of iron. To test the roles of these mechanisms, they incubated fresh, demineralized chicken bone using corresponding treatments to induce collagen crosslinking. Analytical results showed that these treatments did indeed induce the type of crosslinking which is expected to make the collagen more resistant to decomposition. Also, the preserved dinosaur tissues were found to be sufficiently crosslinked to withstand a chemical which cleaves lightly-crosslinked molecules:
Demineralized chicken tissues incubated according to Fenton’s reaction and glycation yielded products consistent with induced hypercrosslinking… Both treated chicken tissues developed small ester peaks (approximately 1732 cm-1); in comparison, a prominent ester peak was observed in all FTIR spectra collected for Tyrannosaurus rex. Fossil vessels treated with the reducing agent [NaBH4, which can cleave low-order intermolecular crosslinks] yielded no significant changes in FTIR analysis, suggesting that the non-enzymatic crosslinks formed in this tissue are irreducible. Such bond formations occur between three or more peptide strands, and as such, tend to be highly resistant to reductive cleavage.
Assessment of Evidence That Soft Tissue Can Persist for 70 Million Years
As might be expected, young earth creationists have taken these observations of soft tissue from dinosaur bones as evidence that these fossils cannot be more than a few thousand years old – and therefore, conventional geological methods like radioactive dating must be terribly flawed, since these methods show the rock layers entombing these fossils as being about 70 million years old.
I cited a couple of these young earth articles at the beginning of this article. Googling “dinosaur soft tissue age earth” produced thousands of results. Dozens and dozens of these hits are sites promoting young earth creationism, claiming that Schweitzer’s results disprove evolution and radioactive dating of rocks. Some of these sites misrepresent the facts, stating that actual red blood cells have been found. As noted above, that is not the case: these little round red things are chunks of iron oxide, like rust, which just happen to be about the size and shape of red blood cells. The actual organic remains are highly crosslinked remnants of a several proteins which are known to have stable structures. These remnants retain the shape of the original soft tissue, which is not surprising, since they were confined within tiny pores in the dinosaur bones.
The main attack by young earth creationists on the antiquity of these finds is an argument from incredulity, based on ignorance: “It is obviously impossible for any trace of soft tissue to endure for 70 million years.” But, how do they know that it is impossible? They don’t. Yes, experiments on protein degradation in test tubes indicate that proteins would break down completely within about a million years. But lots of examples show that the rate of protein degradation varies wildly, depending on the conditions, so no one can say with certainty how long some fragments of protein can last, preserved with iron and sealed in mineral pores. We simply don’t know how this process progresses over a span of millions of years. It is difficult to devise definitive experiments to mimic that timespan.
The ostrich vessels discussed above had their lifetime before degradation extended from three days to more than two years, a factor of over 240. We can even see widely differing decomposition rates in our food, depending on how it is treated. If you leave a jug of milk on the counter for two weeks, lots of biochemistry will take place (mainly lactose fermentation to acids but also including protein degradation) which may render it unfit for human consumption. However, if the milk is contacted with the right bacteria and other materials, the milk proteins can be preserved in the form of cheese which can sit stably on the shelf for years. Similarly, if beef is ground to hamburger and left in a package on the counter for a week, it will rot. However, if the beef is sliced thin and dried to jerky, it will last for months. Same milk and same beef, but with a different set of conditions they can retain proteins for ten or a hundred times longer, depending on their circumstances.
To take another example, in forensic studies at the University of Tennessee “body farm”, donated corpses are deliberately placed on or in the ground to naturally decay so researchers can track exactly how they decompose as they go through the stages of bloating, consumption by maggots, etc. From studies like there, we know that the flesh and skin can decay off a human in about a month under humid conditions. So, after a month, a man’s face may look something like this:
Now, consider this individual:
When he was discovered in a Danish peat bog, looking so dapper, the police were summoned on the assumption that he was a recent murder victim. This “Tollund Man” was in fact a murder victim, but the crime (likely a ritualistic human sacrifice) took place over 2200 years ago. It happens that the chemical conditions in the bog into which he was thrown facilitated preservation of skin and some other soft tissue. Notice that with this and other bog-persons, the wrong approach would be to insist that, because normally human skin does not endure for thousands of years, they must have died recently. Instead, researchers took into account other dating information to realize these bog people were over a thousand years old, even though the preservation mechanism was not initially known. Comparing 2200 years of preservation here, versus complete flesh decomposition within a month on the Tennessee body farm, we have a factor of more than 25,000 difference in rates of soft tissue degradation.
This again makes the point that rates and modes of protein and soft tissue decomposition can vary dramatically, depending on circumstances. Thus, it is absurd to say that because proteins disappear in a million years under one set of conditions, therefore protein remnants could not endure for more than 100 million years under some other conditions. The claim that “We know that substantial fragments of proteins, even in some cross-linked form, cannot survive for 80 million years” is simply not true. Since that claim (in one form or another) is at the heart of the young earth interpretation of these fossil tissues, the young earth case here collapses.
Invariance of Radioactive Decay Rates
We may contrast the uncertainties regarding biological decay, to certainties regarding the physical decay of radioactive elements. These decay rates have been measured in many laboratories in many ways for many years, and they are essentially invariant. There are some particular circumstances where radioactive decay rates can be accelerated, but these are well-understood within the framework of physics. For instance, in a nuclear reactor or bomb, an artificially high density of uranium means that the neutrons from one splitting nucleus have a high probability of striking another nucleus and causing it to split. Also, the “s” shell electrons interact with the nucleus, so perturbing these electrons can affect the nuclear decay rate, sometimes dramatically. However, these effects are understood and predictable. See Wikipedia article “Radioactive Decay” for more on this; this article also notes that many independent observations indicate that nuclear decay rates have been constant for millions of years: “Comparison of laboratory experiments over the last century, studies of the Oklo natural nuclear reactor (which exemplified the effects of thermal neutrons on nuclear decay), and astrophysical observations of the luminosity decays of distant supernovae (which occurred far away so the light has taken a great deal of time to reach us), for example, strongly indicate that unperturbed decay rates have been constant (at least to within the limitations of small experimental errors) as a function of time.”
Since radioactive dating militates for an old earth, of course young earth creationists will not concede to its validity. They advance various objections, but these objections have been refuted over and over again by practicing scientists. For instance, see these resources:
Radiometric Dating A Christian Perspective – – This is a classic, in-depth discussion of radioactive dating of rocks, by an evangelical scientist.
What evidence is there for the earth being billions of years old? [by Russell Downs at BibleQ.net] Brief discussion of radioactive dating of rocks, answering objections raised by YE creationists.
Radiometric Dating Does Work! – – By geologist and National Medal of Science winner Brent Dalrymple. Delves into several detailed examples, including the Hell Creek formation.
For my part, I have documented the errors of young earth arguments regarding the dating of Grand Canyon rocks, and the dating of some recent lava flows. I have also compiled some other physical evidences (e.g. annual layers in lakes and in glacial ice) which demonstrate that the earth is much older than 6000 years.
It would be tedious to retrace all those prior discussions. Thousands and thousands of radioactive dating measurements have been made, so naturally there will be a few that give anomalous results. For many of these cases, it can be seen why the results were odd – for instance, the rock sample may have been re-heated after it initially solidified, which partially re-set the atomic clock. It is disingenuous for young earth proponents to focus on these relatively few anomalous results, and wave away the estimated 95% of radioactive dates that fit precisely with the ancient dates from other, independent dating methods.
If some reader is convinced he is in possession of evidence that radioactive dating fails, then he should inform the larger scientific community of these findings. To overturn the last hundred years of physics would merit a legitimized platform to tell the world at large that old-earth dating methods are unreliable. It might even merit a Nobel Prize. The standard young earth creationist excuse for not doing this is: “But those close-minded godless scientists will not allow publication of anything that threatens their paradigm.” I didn’t say it would be easy, but determined mavericks can always find a way to get their findings into scientific discussion, if there is any merit to their case. Young earth geologists have been allowed to present a number of papers and to lead field trips at recent meetings of the secular Geological Society of America, so it is in fact possible to get a hearing among geologists for an unusual perspective, as long as there is solid supporting data.
That said, let’s look briefly at the standard geological dating for the Hell Creek formation from which Mary Schweitzer’s dinosaur fossils were chipped. All over the world, an abrupt change in the animals represented in the fossil record can be recognized at the boundary between rocks of the Cretaceous (“K”) period, and the overlying Paleogene (formerly called “Tertiary”) rocks. This change in fauna has been obvious for over a century. In a number of locations a thin layer of glassy “tektites”, which are fallout from a giant meteorite strike on the earth, are found right at that boundary. Many independent radiometric measurements have been made on these tektites, consistently showing them to be around 64-66 million years old.
This “K–Pg” (formerly “K-T”) boundary is also marked all over the world by iridium deposits, which again are consistent with a huge asteroid impact. (Meteorites can contain much higher levels of iridium than found in normal earth rocks). Although the exact mechanism of the catastrophe is not clear, it is widely thought that this meteorite strike is tied to the mass extinctions of some three-quarters of plant and animal species on Earth, including all non-avian dinosaurs, which occurred at that time.
There is such an iridium anomaly at the top of the Hell Creek formation. Immediately above this in many spots is a thin bed of coal (the “Z-coal”), which is marked by a white arrow in the photo below.
There are some bentonite clay layers within this coal bed, which incorporate minerals from contemporary volcanic ashfalls. Some of these minerals (e.g. sanidine, biotite, zircon) are amenable to radiometric dating. Since the Z-coal lies just above the Hell Creek formation, the Z-coal was deposited somewhat later. Thus, the dinosaur fossils in the Hell Creek rocks must be older than the Z-coal.
Here are some radioactive datings of ash-containing layers at the Z-coal bed, from a table compiled by U.S. Geological Survey radiometric dating expert Brent Dalrymple. (See further discussion on these data in endnote , showing that these data are not “cherry-picked”, but instead accurately represent the results from dating these layers):
Material Method; Number of Analyses Age in Millions of Years
Sanidine 40Ar/39Ar total fusion; 28 64.8±0.1
Sanidine 40Ar/39Ar age spectrum; 1 66.0±0.5
Sanidine 40Ar/39Ar age spectrum; 1 64.7±0.1
Sanidine 40Ar/39Ar total fusion; 17 64.8±0.2
Biotite, Sanidine K-Ar; 12 64.6±1.0
Biotite, Sanidine Rb-Sr isochron; 1 63.7±0.6
Zircon U-Pb concordia; 1 63.9±0.8
Source: G. Brent Dalrymple ,“Radiometric Dating Does Work!” ,RNCSE 20 (3): 14-19, 2000
This shows that three completely different radioactive dating methods, applied to three different minerals, all gave the same dates, within a spread of only 4%. (Ar/Ar dating is basically K-Ar dating, with improved cross-checking built in). Moreover, these dates are very close to the dates (64-66 million years) determined elsewhere for the tektites that mark the K-T boundary. This uniformity of nuclear radioactive decay stands in stark contrast to the enormous and unpredictable variations in the rate of the biological decay of soft tissues discussed above.
Thus, it is irrational to use the unexpected perseverance of flexible tissues in dinosaur bones as ground to reject the radioactive dating of the rock layers in which these bones were found. But that is what the young earth creationists are trying to do. This just makes them, and their version of the Christian faith, look silly.
The Dinosaur-Bird Connection
Dinosaurs were clearly reptiles, and so the normal expectation would be that the protein sequences recovered from dinosaur fossils would more closely match extant reptiles than any other class of living animals. However, mainstream scientists, guided by the hypothesis of evolution and the common ancestry of all animals, have a different expectation. They would predict that the proteins from dinosaurs would be closer to birds than to any living reptiles.
Here is why: when scientists systematically group species by shared characteristics (cladistic analysis) they consistently find that birds are most closely related to the dinosaurs known as theropods. They share so many characteristics  that extinct and living birds are usually classified as lying within the theropod group. (It should be noted that birds have continued to diverge from their reptilian origins over the past 150 million years. Most modern birds no longer display features like teeth or claws on their wings, which were more prominent in earlier fossil birds, so birds now look very unlike reptiles.)
Below is a cladogram of a branch of reptiles known as “Archosaurs”. Dinosaurs (“Dinosauria”) appear at the lower right of this figure.
Nearly all of these groups are extinct, and thus are known only from fossils. I put red boxes around the only two groups that have living representatives. These are the Crocodylmorpha (today’s crocodiles and alligators), and Theropoda, represented only by today’s birds. Other extant reptiles, such as lizards, snakes, and turtles, lie on entirely different branches of the evolutionary family tree, and thus are considered more distant from dinosaurs. I underlined two key dinosaur types (Tyrannosaurus and Hadrosaurs or duckbills) which figure in the academic work discussed above.
According to this cladistic scheme, dinosaurs are more closely related to birds than to any living reptile, and so the proteins extracted from the dinosaur bones should resemble bird proteins more than alligator or crocodile proteins, even though dinosaurs are reptiles like crocodiles. And that turns out to be the case: the protein sequences from the dinosaur bones do match birds more closely than alligators or crocodiles. Also, the PHEX antibody OB 7.3 which bound strongly to the dinosaur osteocytes cell remnants, binds to osteocytes from today’s birds, but not to osteocytes from reptiles like alligators. This again suggests that dinosaurs are more closely related to birds than to today’s reptiles.
Also, a key observation by Mary Schweitzer in 2003, published in 2005 , was that the T. rex thighbone in her possession displayed distinctive zones of medullary bone. As noted above, medullary bone temporarily appears within female bird bones, where it serves as a reservoir of calcium for producing the shells of eggs. In 2007 Lee and Werning  reported medullary bone in fossils of two other dinosaurs, the theropod Allosaurus and the ornithopod Tenontosaurus. Among today’s animals, medullary bone is only found in birds, not in reptiles. Thus, medullary bone “is an independent line of evidence supporting a close phylogenetic relationship between dinosaurs and birds” .
Thus, as happens again and again, predictions based on evolution were borne out upon experimental investigation.
Side comment on the dinosaur-bird connection: in most areas of science, there are a few hold-out researchers who cling to some position they took years ago (which was perhaps reasonable, based on the state of the data at the time), and do not fully engage with more recent evidence showing that they are wrong. For instance, brilliant astronomer Fred Hoyle went to his grave rejecting the Big Bang origin of our universe, despite the plethora of confirming evidence in the 1960’s and onward. Astrophysicist Thomas Gold, winner of many prestigious scientific awards, proposed in the 1950’s that gas and oil fields in the earth’s crust stemmed mainly from inorganic reservoirs or processes deep in the earth’s mantle. That was a decent proposal for the 1950’s, but he never changed his view after decades of results which showed unambiguously that petroleum derives from layers of deceased organisms that settled to the floors of ancient seas and lakes.
Similarly, there are a few researchers today who do not accept the bird-therapod evidence which has accumulated from fossil finds of the past two decades. Young earth creationists like to cite these mavericks as evidence that secular paleontology is in hopeless disarray. However, these skeptics seem to misunderstand the fossil evidence that does exist, and they fail to present competing testable cladograms. The University of California Museum of Paleontology puts it :
Some researchers today do not agree that dinosaurs gave rise to birds, and are working to falsify this theory, but so far the evidence for the theory has swamped their efforts… Some researchers have raised issues that may seem to make the theropod origin of birds difficult to support, but these difficulties are more illusory than substantial. One proposed difficulty is the gap in the fossil record between the first known bird (Late Jurassic) and the dromaeosaurs, probable sister group of birds (Early Cretaceous). This overlooks the blatant fact that other maniraptoran coelurosaurs, such as Ornitholestes, Coelurus, and Compsognathus, are known from strata of Late Jurassic age. If other maniraptorans were there, it logically follows that the ancestors of dromaeosaurs were there…
Other arguments, such as the putative differences between theropod and bird finger development, or lung morphology, or ankle bone morphology, all stumble on the lack of relevant data on extinct theropods, misinterpretations of anatomy, simplifying assumptions about developmental flexibility, and/or speculations about convergence, biomechanics, or selective pressures. The opponents of the theropod hypothesis refuse to propose an alternative hypothesis that is falsifiable.
And now with Schweitzer’s work, the chemical analysis of the tissues from dinosaur bones has further supported the bird-dinosaur connection.
After Prof. Schweitzer showed it was possible to rigorously analyze protein remnants that are many millions of years old, many other researchers have trained their instrumentation on dinosaur and other ancient fossils. For instance, in 2015 a team from several London-area institutions used focused ion beam (FIB) sputtering to cut into fossil samples from eight Cretaceous dinosaurs. Bertazzo et al.  used various techniques such as electron microscopy and secondary ion mass spectrometry (SIMS) to examine the successive surfaces which were exposed by the ion beam etching. In four of the samples, they observed some carbon-rich fibrous structures which resemble the calcified collagen fibers found in modern bone. If these are original dinosaur tissue, these fibrous structures could be retaining the quaternary structure of the collagen proteins. However, until the proteins are actually sequenced, we cannot be sure that this is original tissue. Also, the mineral matrix in the fossils may have served to permanently fix the original fibrous structures in place, regardless of the eventual conformation of the proteins.
In a claw from a therapod dinosaur, Bertazzo et al. observed some carbon-rich structures which bear superficial resemblance to red blood cells (erythrocytes). The mass spec results are consistent with the presence of some sort of protein in this location. As we have pointed out repeatedly, the decomposition of biological materials varies enormously, depending on the sample history, so it is conceivable that some remnants of red blood cells have survived in this dinosaur claw. This would pose no challenge to the great antiquity of these specimens, since we already know that proteins can endure for millions of years. These structures are embedded in a mineral-rich “cement”, which might have served as a rigid cast to preserve the shape of some original cells and to keep their proteins trapped and protected from bacteria.
However, as with the fibrous structures, it will take protein sequencing to determine what is really there. Scientists have repeatedly observed things which looked like red blood cells, but turned out not to be. For instance, photos near the beginning of this article from Schweitzer and from Thomas Kaye both show little round red things the size of red blood cells sitting right there in blood vessels, but which were not in fact red blood cells. Thus, the true nature of the structures observed by Bertazzo et al. remains to be determined. A reason to suspect that these are not red blood cells is that they are only about 2 microns in length. This is very much smaller than the size of red blood cells in modern birds (9-15 microns) or reptiles (14-20 microns). It is doubtful that linear shrinkage can account for this magnitude of discrepancy. An Answers in Genesis article acknowledges that the size of these structures casts doubt on whether they are from red blood cells .
The popular press has not been able to overcome the temptation to sensationalize these findings. A BBC piece  started off with a proper headline which enclosed “blood cells” in quotes to denote the tentative nature of this finding, and ended with a brief interview with Mary Schweitzer who cautioned, “They did find amino acids consistent with proteins, but the data they presented do not really identify which proteins; for that they need additional data.” However, in the middle the reporter lapsed into mistakenly referring to these structures as outright “red blood cells”. The headline on an article in The Guardian  gleefully proclaimed “75-million-year-old dinosaur blood and collagen discovered in fossil fragments ”. It is only near the end of that article that the admission was made that “More work is needed to be sure the features are genuine blood cells and collagen.”
Mary Schweitzer on Creation
On November 15, 2009, 60 Minutes aired an interview with Mary Schweitzer and her former professor, famed paleontologist Jack Horner. Horner got most of the air time at the beginning of the interview (largely focusing on his connection to the film Jurassic Park), and at the end with his sensational proposal to resurrect dinosaurs from chicken DNA. The more hard-science part is with Schweitzer, in the 5:00-11:30 time slot of this 14-minute piece. Below is a screen shot from her interview, and here is a link to the YouTube version.
Schweitzer reviews and recreates some of the key discoveries discussed above. She shows how perilous was one of the fossil excavations, and she has the interviewer, Lesley Stahl, get her tongue stuck to the highly porous dinosaur fossil bone.
The Comments on this YouTube video are mainly by young earth creationists, proclaiming that Schweitzer’s finds prove the earth is young. For instance:
Proof that the world is only 6,000 years old, and these dinosaur tissue is still good because they only died recently during the flood! =D
“Oh wait, they found what inside dinosaur bones???!!!!! That must mean soft tissue can last 70 million years. No other possible explanation. At least no other explanation that satisfies our faithless Bible-hating selves.” – Average secular scientist
looks like the Bible is correct and evolution is a fairy tail for adults.
The Truth is coming out…Dinosaurs are not dating back 68 million years….they are recent.
Even the very scientists that have found this evidence are amazed at the fact that there should not be soft tissue finds in dinosaurs that are millions of years old. I find it quite comical that they choose to question the biochemical decay rates, and not the amount of years, of course we all know what would happen to them if they did. It is sad when scientists are so brainwashed or fearful that they can’t follow where the evidence leads. I have compared and so far I’ve only heard theories.
this is not imposable GET A LIFE!!!!! you know now that the bible is right all along THE WORLD IS YOUNG! and all your resurch is not worth the paper it is written on!! go read the Bible save yourself more money that you will ever see. and save yourself more time than you will EVER!! have. what a Dinosaur Just go get one in the swamps of the Congo. Dinosaurs are not extinct
And so on. Some of these comments are more thoughtful than others, but they all demonstrate the widespread grass-roots support for the young earth creationist perspective.
(Side comment on “swamps of the Congo”: some young earth creationists pin their hopes on ephemeral sightings of a creature supposedly resembling a dinosaur, in the steaming heart of the Dark Continent. In the unlikely event that these rumors are substantiated, and we do find that some species of reptilian dinosaur has survived till today, that would do nothing to prove a young earth. All it would show is that the fossil record is inherently incomplete, which is what evolutionists have been claiming all along as a reason why so few direct intermediate fossils are found. Nothing in evolutionary theory demands that every dinosaur species went extinct at the K-Pg boundary.)
It is clear from this interview that Mary Schweitzer is an intelligent, good-hearted person. But is she a “godless evolutionist”? As it turns out, she is a “godly evolutionist”. From a 2006 interview with the Smithsonian:
She describes herself as “a complete and total Christian.” On a shelf in her office is a plaque bearing an Old Testament verse: “For I know the plans I have for you,” declares the Lord, “plans to prosper you and not to harm you, plans to give you hope and a future.”
It is likewise clear in a 2014 interview with Biologos  that Schweitzer is a conservative, evangelical Christian:
I do go to pretty conservative churches… I go to church because I want to learn and be held accountable. I want to learn more and more about what the Bible teaches… Everyone has to figure out what they need and why they go to church. The hunger in me which is fed in the churches I go to has to do with the fact that they preach right out of the Bible, and I need that. I guess I don’t go to church to hear political views and hear about how they need money—I go to hear about God.
Growing up with a conservative Christian background, she had believed that the secular science establishment promotes themes like evolution out of a desire to discredit biblical faith. However, when she took an actual paleontology class, she saw things differently :
I think the thing that surprised me most about that class was that I had no idea, coming from a conservative Christian background, that scientists are not all trying to disprove God in whatever way they can. What we were not told growing up is that there’s a lot of very rigorous, hard science that allows us to interpret the lives of organisms we’ve never seen—and knowing this made me rethink a few things, because I know God and God is not a deceiver. If you step back a little bit and let God be God I don’t think there’s any contradiction at all between the Bible and what we see in nature. He is under no obligation to meet our expectations. He is bigger than that.
With her experiences, she is able to help students coming from a young earth background to cope with the shock when they realize that mainstream science is true and what their parents told them about science is false :
I think that parents need to tell their kids that there are a lot of REASONS scientists say what they do, and virtually NONE of those reasons are to disprove God’s existence. That doesn’t enter in. I’ve had lots of students come into my office in tears over the years, saying, “I don’t understand…”
She has been dismayed by how young earth creationists have misused her results:
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. They’re looking at this research in terms of a false dichotomy [science versus faith] and that doesn’t do anybody any favors. 
She’s horrified that some Christians accuse her of hiding the true meaning of her data. “They treat you really bad,” she says. “They twist your words and they manipulate your data.” 
Sometimes she can graciously negotiate differences of opinion :
One time I was visiting a church and the pastor got up and started preaching a sermon about people not being related to apes, and he started talking about this scientist in Montana who discovered red blood cells in dinosaur bones—he didn’t know I was in the audience—and it was my research he was talking about! Unfortunately, he got everything wrong. I just got up and left…
One of the churches I go to is very conservative—But the pastor and I have discussed what I do, and we have agreed to disagree on some things. I think that’s the appropriate attitude to have—after all, God is the only one who knows for sure—he is the only one who was there.
But sometimes it gets personal and ugly:
It’s also hard because, being a Christian evolutionary biologist, I receive a lot of mail that is not fun—fellow Christians suspect my faith, and scientific colleagues suspect my science. But I have no agenda, except to produce data… I’ve gotten a lot of pretty cruel, harsh, judgmental emails over the years—and if you’re a Christian saying things like that, it’s no wonder my colleagues don’t want anything to do with faith. Christianity is about love, and these are not really loving responses to anything. 
To Mary Schweitzer, young earth creationism errs theologically as well as scientifically:
Science and religion represent two different ways of looking at the world; invoking the hand of God to explain natural phenomena breaks the rules of science. After all, she says, what God asks is faith, not evidence. “If you have all this evidence and proof positive that God exists, you don’t need faith. I think he kind of designed it so that we’d never be able to prove his existence. And I think that’s really cool.” 
As she continues to study the complexities of God’s world with this perspective, her faith is not threatened, but rather is deepened:
I don’t feel that I’m discrediting God with the work I’m doing, I think I am honoring him with the abilities he’s given me…. The more I understand how things work, the bigger God gets. When he was just a magician pulling things out of a hat, that doesn’t even compare to how I see him now! 
The work by Mary Schweitzer and her colleagues has shown that at least some of the flexible tissues from deep within the dinosaur bones she examined is original organic material, not merely recent biofilm. However, these tissues have been significantly stabilized by cross-linking in the course of aging. While there is evidence for some heme units (heme is a stable portion of hemoglobin), there are no actual red blood cells.
For other fossil dinosaur samples, it is possible that the flexible material found in them is recent bacterial biofilm, not original organic molecules. Thomas Kaye presented convincing evidence that some of the flexible material he extracted from fossil dinosaur or turtle remains was biofilm. He also found that little red objects which initially looked like red blood cells in blood vessels were actually microclusters of iron oxide.
Some possible factors in preserving original organic matter in dinosaur bones are rapid initial drying of the carcass; hermetic sealing and intimate contact with a mineral surface within tiny bone pores; and cross-linking catalyzed by iron. A controlled laboratory experiment showed dramatic preservation of blood vessels in the presence of a high concentration of extracted hemoglobin.
The rate of decomposition of organic matter in buried corpses was shown to vary wildly. Many factors remain poorly understood, and so statements like “Original organic tissues cannot possibly endure for 70 million years” are insupportable. We simply do not know. In contrast, the physics of dating rock layers (including the layers in which these dinosaur bones were found) is well-understood and reproducible.
That scientists are unable at present to give a complete account of the mechanism and trajectory of the preservation of modified proteins in the dinosaur bone pores is not some unique, embarrassing case. This situation arises constantly in the course of scientific discovery. At the leading edge of most fields of physical science are always some observations which cannot currently be completely accounted for, and which call for further investigation. That is precisely how science advances. For instance, in 1896 when uranium compounds were found to cause exposure of photographic plates wrapped in black paper, there was no mechanistic explanation. Scientists did not throw up their hands and say, “We can’t explain this, so modern science is worthless!” No, they kept making observations, and kept learning more, and eventually realized that the nuclei of atoms were emitting radiation that could penetrate black paper.
Again and again young earth creationists have pointed to some observations such as bent rock layers, polystrate fossils, the amount of salt in the ocean, apparent mingled human and dinosaur footprints, the amount of helium in the atmosphere, polonium halos, or fluctuations in the earth’s magnetic field, and claimed that since conventional (old-earth) science could not explain these observations, the earth must be young. But when genuine science is brought to bear on these issues, they are eventually readily explained within the framework of an old earth and accepted physics. It may take some years, however, to come to a satisfactory resolution. A number of these supposed evidences for a young earth are exposed here .
The absence of long, sequenceable chains of DNA in any dinosaur fossils indicates that these fossils are much older than the 6000-4500 year age allowable in young earth creationism. The traces of DNA fragments in Schweitzer’s fossils matched more closely to modern birds than to modern reptiles. The same held true for sequences of proteins. These trends conform to evolutionary expectations, since most biologists hold that today’s birds are direct descendants of dinosaurs, whereas today’s alligators are more distant cousins.
Mary Schweitzer is a dedicated evangelical Christian, who has born with grace the attacks on her character and the misrepresentation of her work by young earth creationists.
ADDENDUM: The transcript of a July, 2016 interview with Mary Schweitzer, retracing how she got started in paleontology and how it affected her faith, is here. She notes that she initially audited a class in paleontology because she was (at that time) a young earth creationist and planned to show the professor that his evolutionary views were wrong. That experience of coming to terms with the scientific data while maintaining the essentials of her Christian faith has prepared her to help students at her university who are dealing with the same issue:
I’ve actually had students in my office struggling with this same thing, saying, “I think I’m going to have to throw away my faith.” You know, as Christians, as parents, we do our students a huge disservice if we don’t prepare them to see the scientific data someday — on a whole range of things. We need to help them hang onto their faith and to understand why scientists are saying what they’re saying and that their faith is not incongruent with science. To me it is so exciting to see God revealed through science.
APPENDIX: CARBON DATING OF DINOSAUR BONES
Doing carbon 14 dating on dinosaur fossils often gives dates of 20,000-40,000 years old, and trying to carbon date things like graphite and diamond often gives dates of around 50,000 years old. That is exactly what we expect when a dating method is pushed to its limits and beyond. The amount of C14 in the (modern) atmosphere is only about one C14 in a trillion other carbons. For older samples, the remaining amount of C14 declines and declines until at around 50,000 years old it is less than one C14 in 300 trillion other carbon atoms, which is about the practical limit of accurate detectability with existing instrumentation.
Part of the “practical limit” caveat is that the air, the water, and the ground are swimming in modern levels of C14, and it takes only the merest bit of modern contamination to make something made of solid carbon (e.g. graphite or diamond) that is a million years old look like it is 50,000 years old. And it only takes a little more modern C14 contamination to cause a semi-porous dinosaur fossil which is not solid carbon and which for thousands of years has been in contact with water laden with modern carbonate ions and organic compounds to return a date of 20,000-40,000 years. (Folks try to remove modern contaminants, but you can’t get them all).
So there are known, intrinsic problems with trying to date really old things (especially things buried in the ground) with C14. The carbon dating method is working with vanishingly small amounts of C14, contamination with modern carbon is unavoidable, and the effects of that contamination become dominant for more ancient samples. We are essentially guaranteed to come up with an apparent “date” of 15,000-60,000 years, no matter how much older the sample actually is. That is the simple physical reality of carbon dating, which young earth creationists do not want to admit. Instead, they claim that these apparent dates demonstrate that these samples cannot be millions of years old. This is just another falsehood.
In contrast, radioactive dating of the rock layers (e.g. Hell Creek formation in Montana, using Rb-Sr or U-Pb dating) where many dino fossils are found does not suffer from these problems. (a ) There are reasonably high concentrations of the parent and daughter elements to work with, and (b) there is little chance of contamination from the environment. For instance, the air and water around us is not chock-full of Rb or Sr or U or Pb , and so there is not much of a chance that adventitious Rb or Sr or U or Pb will penetrate into the minerals that contain these elements enough to alter the radiogenic dates. (Not to say this cannot possibly happen, but it is extremely unlikely; the fact that different dating methods nearly always give the same date for a given rock show that they are reliable). Ar is present at appreciable concentration (1%) in the atmosphere, but the Ar39/Ar40 method can detect whether atmospheric contamination has taken place.
Furthermore, the old dates from radioactive dating of rocks are supported by many other physical observations such as lake varves, annual layers in glacier ice cores, the positions and current movements of the earth’s crustal plates, rock formations like unconformities, etc. etc. (see https://letterstocreationists.wordpress.com/2014/09/07/some-simple-evidences-for-an-old-earth/ )
So – – we have one dating method with known, unavoidable problems for dating really old things, giving results which are at variance with a whole battery of other methods which are good at dating really old things. This is why practicing scientists do not regard the C14 results on dinosaur fossils as indicative of their actual dates.
See README for a description of other research articles on this blog
 Thomas, B. 2009. Dinosaur Soft Tissue Issue Is Here to Stay. Acts & Facts. 38 (9): 18 http://www.icr.org/article/4827
 M. H. Schweitzer, “Blood from Stone”, Scientific American, December, 2010, pg. 62. http://www.scientificamerican.com/article/blood-from-stone/
 Mary Schweitzer and Tracy Staedter, “The Real Jurassic Park,” Earth (June 1997): 55–57 , as cited by Reasons to Believe in: http://www.reasons.org/articles/dinosaur-blood
 Mary Higby Schweitzer, John R. Horner Annales de Paléontologie, Volume 85, Issue 3, Pages 179-192 (1999) http://www.sciencedirect.com/science/article/pii/S0753396999800135 (abstract only)
 Hai-Lin Wang, Zi-Ying Yan, and Dong-Yan Jin , Reanalysis of Published DNA Sequence Amplified from Cretaceous Dinosaur Egg Fossil, Mol Biol Evol (1997) 14 (5): 589-591. http://mbe.oxfordjournals.org/content/14/5/589.full.pdf+html
 : Schweitzer, et al., “Soft-Tissue Vessels and Cellular Preservation in Tyrannosaurus rex”, Science, 307 (2005) 1952. http://www.rpgroup.caltech.edu/~natsirt/stuff/Schweitzer%20Science%202005.pdf
 Mary Higby Schweitzer, Zhiyong Suo, Recep Avci, , John M. Asara, Mark A. Allen, Fernando Teran Arce, John R. Horner. “Analyses of Soft Tissue from Tyrannosaurus rex Suggest the Presence of Protein”, Science 13 April 2007: Vol. 316 no. 5822 pp. 277-280. http://www.sciencemag.org/content/316/5822/277.abstract
 John M. Asara, Mary H. Schweitzer, Lisa M. Freimark, Matthew Phillips, Lewis C. Cantley, “Protein Sequences from Mastodon and Tyrannosaurus Rex Revealed by Mass Spectrometry”, Science 13 April 2007: Vol. 316 no. 5822 pp. 280-285 http://www.sciencemag.org/content/316/5822/280.short and http://www-nmr.cabm.rutgers.edu/academics/biochem694/reading/Asara_etal_2007.pdf
 Kaye, et al., “Dinosaurian Soft Tissues Interpreted as Bacterial Biofilms”, PLoS ONE 3(7): e2808 http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0002808
 Schweitzer, et al., “Biomolecular Characterization and Protein Sequences of the Campanian Hadrosaur B. Canadensis”, Science 1 May 2009: Vol. 324 no. 5927 pp. 626-631 http://www.sciencemag.org/content/324/5927/626.abstract
(Here is an accessible summary of this Science 2009 article:
 Schweitzer, et al., Proc. R. Soc. B (2005) 272, 775–784 . http://rspb.royalsocietypublishing.org/content/royprsb/272/1565/775.full.pdf
 Mary Higby Schweitzer, “Soft Tissue Preservation in Terrestrial Mesozoic Vertebrates”, Annual Review of Earth and Planetary Sciences Vol. 39: 187-216 (May 2011) http://www.annualreviews.org/doi/abs/10.1146/annurev-earth-040610-133502
 Theagarten Lingham-Soliara and Joanna Glabb,” Dehydration: A mechanism for the preservation of fine detail in fossilised soft tissue of ancient terrestrial animals”, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 291, Issues 3–4, 15 May 2010, Pages 481–487 http://www.sciencedirect.com/science/article/pii/S0031018210001471
 James D. San Antonio, Mary H. Schweitzer, Shane T. Jensen, Raghu Kalluri, Michael Buckley, Joseph P. R. O. Orgel. “Dinosaur Peptides Suggest Mechanisms of Protein Survival”, PLoS One 6, no. 6 (2011): e20381 http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0020381
 Fazale Rana , “Structure of Dinosaur Collagen Unravels the Case for a Young Earth”, Reasons to Believe, August 10, 2011. http://www.reasons.org/articles/structure-of-dinosaur-collagen-unravels-the-case-for-a-young-earth
 M. J. Collins, C. M. Nielsen-Marsh, J. Hiller, C. I. Smith And J. P. Roberts, “The Survival Of Organic Matter In Bone: A Review”, Archaeometry 44, 3 (2002) 383–39 http://onlinelibrary.wiley.com/doi/10.1111/1475-4754.t01-1-00071/pdf
 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. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0013334
 Mary Higby Schweitzer, Wenxia Zheng, Timothy P. Cleland, Marshall Bern. “Molecular analyses of dinosaur osteocytes support the presence of endogenous molecules”. Bone Volume 52, Issue 1, January 2013, Pages 414–423. http://www4.ncsu.edu/~lezanno/Research_files/SchweitzerEtAl2012.pdf
 Morten E. Allentoft, et al.,”The half-life of DNA in bone: measuring decay kinetics in 158 dated fossils”. Proc. R. Soc. B (2012) 279, 4724–4733 . http://rspb.royalsocietypublishing.org/content/279/1748/4724
 Matthias Meyer, et al., “A mitochondrial genome sequence of a hominin from Sima de los Huesos”, Nature 505, 403–406 . http://www.nature.com/nature/journal/v505/n7483/full/nature12788.html
 Schweitzer MH, Zheng W, Cleland TP, Goodwin MB, Boatman E, Theil E, Marcus MA, Fakra SC. “A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time”, Proc. R. Soc. B 281: 20132741. http://rspb.royalsocietypublishing.org/content/royprsb/281/1775/20132741.full.pdf
 Elizabeth M. Boatman, Mark B. Goodwin, Hoi-Ying Holman, Sirine Fakra, Mary H. Schweitzer, Ronald Gronsky and John R. Horner, “Synchrotron Chemical and Structural Analysis of Tyrannosaurus rex Blood Vessels:The Contribution of Collagen Hypercrosslinking to Tissue Longevity”, Microsc. Microanal. 20 (Suppl 3), 2014 http://infrared.als.lbl.gov/Publications/2014/BGHFSGH14/1430.pdf
 “Are Birds Really Dinosaurs?”, The University of California Museum of Paleontology. http://www.ucmp.berkeley.edu/diapsids/avians.html
 Lee, A. H. and Werning, S. “Sexual maturity in growing dinosaurs does not fit reptilian growth models.” 2007. PNAS 105:2:582-587 http://www.pnas.org/content/105/2/582.full?sid=1a6b4941-c23f-46db-9eda-07ba2b73de0f
 “Medullary Bone and the Dinosaur-Bird Link”, https://dinosours.wordpress.com/2012/01/20/medullary-bone-and-the-dinosaur-bird-link/
 Helen Fields, “Dinosaur Shocker”. Smithsonian Magazine, May 2006 http://www.smithsonianmag.com/science-nature/dinosaur.html?c=y&page=3
 Emily Ruppel, “Not So Dry Bones: An interview with Mary Schweitzer”. July 21, 2014. http://biologos.org/blog/not-so-dry-bones-an-interview-with-mary-Schweitzer
 Evan Ratliff , “Origin of Species: How a T. Rex Femur Sparked a Scientific Smackdown”,WIRED MAGAZINE: 17.07 http://archive.wired.com/medtech/genetics/magazine/17-07/ff_originofspecies?currentPage=all
 Laura Geggel, ” Is It Possible to Clone a Dinosaur?” LiveScience April 28, 2016 http://www.livescience.com/54574-can-we-clone-dinosaurs.html
 Further notes on the dating of the tektites and Z-coal just above the Hell Creek formation:
The table of datings for the Z-coal was taken from Table 2 of the article “Radiometric Dating Does Work!” by G. Brent Dalrymple of the U.S. Geological Survey, in RNCSE 20 (3): 14-19, 2000. The link to this article is given in the article, https://ncse.com/library-resource/radiometric-dating-does-work.
Here is Dalrymple’s commentary in that article on these Hell Creek formation samples, and also on tektites found in Haiti:
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In addition to shocked quartz grains and high concentrations of iridium, the K-T impact produced tektites, which are small glass spherules that form from rock that is instantaneously melted by a large impact. The KT tektites were ejected into the atmosphere and deposited some distance away. Tektites are easily recognizable and form in no other way, so the discovery of a sedimentary bed (the Beloc Formation) in Haiti
that contained tektites and that, from fossil evidence, coincided with the K-T boundary provided an obvious candidate for dating. Scientists from the US Geological Survey were the first to obtain radiometric ages for the tektites and laboratories in Berkeley, Stanford, Canada, and France soon followed suit. The results from all of the laboratories were remarkably consistent with the measured ages ranging only from 64.4 to 65.1 Ma
(Table 2). Similar tektites were also found in Mexico, and the Berkeley lab found that they were the same age as the Haiti tektites. But the story doesn’t end there.
The K-T boundary is recorded in numerous sedimentary beds around the world. The Z-coal, the Ferris coal, and the Nevis coal in Montana and Saskatchewan all occur immediately above the K-T boundary. Numerous thin beds of volcanic ash occur within these coals just centimeters above the K-T boundary, and some of these ash beds contain minerals that can be dated radiometrically. Ash beds from each of these coals have been dated by 40Ar/39Ar, K-Ar, Rb-Sr, and U-Pb methods in several laboratories in the US and Canada. Since both the ash beds and the tektites occur either at or very near the K-T boundary, as determined by diagnostic fossils, the tektites and the ash beds should be very nearly the same age, and they are (Table 2).
There are several important things to note about these results. First, the Cretaceous and Tertiary periods were defined by geologists in the early 1800s. The boundary between these periods (the K-T boundary) is marked by an abrupt change in fossils found in sedimentary rocks worldwide. Its exact location in the stratigraphic column at any locality has nothing to do with radiometric dating — it is located by careful study of the
fossils and the rocks that contain them, and nothing more. Second, the radiometric age measurements, 187 of them, were made on 3 different minerals and on glass by 3 distinctly different dating methods (K-Ar and 40Ar/39Ar are technical variations that use the same parent-daughter decay scheme), each involving different elements with different half-lives. Furthermore, the dating was done in 6 different laboratories and the materials were collected from 5 different locations in the Western Hemisphere. And yet the results are the same within analytical error. If radiometric dating didn’t work then such beautifully consistent results would not be possible.
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Since this 2000 article by Dalrymple is short and written for the layman, it mentions the numbers of measurements and the laboratories which made these measurements, but does not always include the specific references for every data point. However, it is possible to find most of these references on the internet.
For instance, the data in the first row of our table (sanidine, 28 measurements, averaging 64.8 million years) come from his 1993 publication: “40Ar/39Ar age spectra and total-fusion ages of tektites from Cretaceous-Tertiary boundary sedimentary rocks in the Beloc Formation, Haiti“, U. S. Geological Survey Bulletin 2065, by G. Brent Dalrymple, G.A. Izett, L.W. Snee, and J.D. Obradovich.
The link for this publication is https://pubs.er.usgs.gov/publication/b2065 . From that link, the full report can be downloaded. It contains reams of numbers on multiple, replicate measurements on tektites from Haiti and also on sanidine crystals isolated from bentonite layers in the Hell Creek Z-coal. Here is a histogram of the dates from all these measurements:
Some 28 independent measurements were made for the Z-coal, and the results show a reasonably tight distribution between about 64 and 66 million years ago, averaging to 64.8 Ma. For the Haitian tektites (a completely different mineral), 52 measurements are shown. These dates group between about 63 and 66 million years ago.
This 1993 Dalrymple USGS report also gives references for the K-Ar, Rb-Sr, and U-Pb dating results shown in our table , e.g. H. Baadsgaard, J. F. Lerbeko, and I. McDougall, “A radiometric age for the Cretaceous-Tertiary boundary based upon K-Ar, Rb-Sr, and U-Pb ages of bentonites from Alberta, Saskatchewan and Montana”. Canadian Journal of Earth Science, v. 25, p.1088-1097.
Another major study of sanidine dating from the Z-coal layers was by C.C. Swisher, L. Dingus, and R. F. Butler, “40Ar/39Ar dating and magnetostratigraphic correlation of the terrestrial Cretaceous–Paleogene boundary and Puercan Mammal Age, Hell Creek – Tullock formations, eastern Montana”, Canadian Journal of Earth Sciences, 1993, 30(9): 1981-1996 . The Z-coal dating here was 65.0 million years ago (datings for various sublevels of this coal group are also given). This 1993 Swisher, et al. article references some eleven prior studies on Z-coal sanidine dating which yielded dates between 63.5 and 66.5 million years ago.
In 2013 Renne et al. revisited the dating of the Z-coal layers above the Hell Creek formation ( P. R. Renne, et al., “Time Scales of Critical Events Around the Cretaceous-Paleogene Boundary”. Science 08 Feb 2013: Vol. 339, pp. 684-687 ). They performed 40Ar/39Ar dating on sanidine from several parts of the Z-coal layers, and again measured an age of about 66 million years. They performed Ar/Ar measurements on K-T boundary layer tektites from Haiti, finding a date of 66 million years there also.
The supplementary material for the Renne, et al. article (www.sciencemag.org/cgi/content/full/339/6120/684/DC1 ) also describes the dating of a set of zircons from the Z-coal layers, using the uranium/lead system. Again, a date of 66 million years was measured.
All this shows that multiple, independent measurements, made in different laboratories over the course of decades, give tight, consistent answers for the date of the rock layers immediately above the Hell Creek formation. This is strong confirmation that this date is reliable, and shows there was no arbitrary “cherry picking” of the data here to obtain harmonious results.
 Beatrice Demarchi, et al., “Protein sequences bound to mineral surfaces persist into deep time”, eLife 2016;5:e17092 . https://elifesciences.org/content/5/e17092
 “Fibres and cellular structures preserved in 75-million–year-old dinosaur specimens”, Nature Communications 6, Article number: 7352 (2015)http://www.nature.com/articles/ncomms8352
 https://answersingenesis.org/fossils/preserved-cretaceous-collagen-and-dinosaur-blood-common-clues-catastrophic-past/ “The extraordinarily small size of these cell-like structures should at least raise the possibility that they have been misidentified. Given their remarkably small size, we must at least hold open the possibility that they are not blood cells at all. ”
COPYRIGHT SCOTT BUCHANAN 2015 Permission is granted for reproduction for non-commercial use of this text as long as the contents are not altered and attribution is given. The figures are attributed separately.