INTRO BY JIM: Paleontologist Mary Schweitzer made worldwide headlines in 2005 for announcing that she had discovered soft tissue preserved in 65 million year old dinosaur fossils. Those who deny the scientific evidence for the old age of the earth have attempted to leverage this discovery to cast doubt on dating methods. But that is a misrepresentation of her findings. Scott Buchanan has meticulously poured through the details of Schweitzer’s work and presented it on the blog, Letters to Creationists. He gives us here a summary of the issues. See also our interview with Schweitzer herself on the blog last year.
For fossils as old as dinosaurs (over 65 million years), the conventional wisdom has been that no original proteins from once-living cells could remain. If the delicate structure of soft body parts is discernable in a fossil, that is normally because these parts were converted to some type of hard mineral during the fossilization process. However, over the past two decades, paleontologist Mary Schweitzer has rocked the world of paleontology by presenting visual evidence of soft tissues recovered from the interior of dinosaur bones, and biochemical evidence indicating that these are in fact the remnants of the original cells and structures from within the dinosaur bone pores. For instance, here is a network of blood vessels, containing little round red things that look like red blood cells:
High magnification of dinosaur vessels shows branching pattern (arrows) and round, red microstructures in the vessels. Source: Schweitzer, et al., “Soft-Tissue Vessels and Cellular Preservation in Tyrannosaurus rex,” Science, 307 (2005) 1952. Reprinted with permission.
Young earth creationists have widely cited these findings as evidence that dinosaur fossils cannot really be millions of years old, and so the rock layers (radioactively dated to more than 65 million years of age) cannot really be millions of years old—and so, it is claimed, the whole old-earth dating edifice collapses. There are multiple reasons why these claims are false. I have read through most of Schweitzer’s papers on this topic, and reviewed the key findings from them in a 25-page article, which is posted on the Letters to Creationists blog as “Dinosaur Soft Tissue.” For lots of data and literature references, that is the place to go. For those who do not want to wade through all that information, here are some key takeaways:
Tissues and Proteins Identified in Dinosaur Bones
These remarks pertain mainly to thigh bones from two dinosaur specimens, a T. rex (approx. 68 million years old) and a duckbill hadrosaur (approx. 80 million years old). In both cases, the fossils had been buried in sandstone (which may help wick away destructive enzymes from the corpse) and the fossils were analyzed within a relatively short time after excavation, which minimized degradation from sudden exposure to a new set of environmental conditions.
After dissolving away the mineral portion of the bone with weak acid, various types of flexible structures were recovered. They conform to the microscopic pores of the bone in which they had resided, so they are mainly viewed under a microscope. These structures include transparent, branching hollow vessels corresponding to the blood vessels found in modern animals (e.g. ostriches), and also what look like modern osteocyte (bone) cells. Various biochemical tests have indicated that these structures are composed of animal protein, showing that they derive from the original dinosaur tissue, as opposed to being merely biofilms produced by microbes which invaded the bone pores.
The proteins which have been identified include collagen, actin, and tubulin. These are known to have structures which are resistant to degradation, especially when they are crosslinked. Tests indicate that these proteins from the dinosaur bones are indeed highly crosslinked, which appears to be a key aspect of their longevity.
Iron from blood hemoglobin can be highly effective in promoting this crosslinking and in general passivating the reactive groups on the proteins. Schweitzer’s group performed a dramatic experiment to demonstrate this effect, using modern ostrich blood vessels: the blood vessels which were incubated in a solution of hemoglobin (extracted from the red blood cells of chicken and ostrich) showed no signs of degradation for more than two years. In contrast, the ostrich vessels in plain water showed significant degradation within three days, which is more than 240 times faster degradation than with the hemoglobin. The osteocyte cell remnants from dinosaur fossils are essentially coated with iron-rich nanoparticles.
Beside the effect of iron, being in contact with the mineral walls of the pores, and being sealed in tiny pores, away from the enzymes and other body chemicals, can act to preserve remnants of the original proteins. Also, if soft tissue is initially dried out before it decays, it undergoes changes that make it more stable even if it is later rehydrated. Thus, several plausible mechanisms are known to help explain the preservation of these flexible tissues, and there are likely other factors yet to be discovered.
Wide Variations in Tissue Decay Rates
There are plenty of other examples of wide difference in the rates of tissue degradation, besides the ostrich blood vessels cited above. For instance, raw meat may spoil in a few days at room temperature, but will keep for weeks in a refrigerator, and for years if it is frozen or (in the case of country hams) if it is treated with salt and smoke. All the flesh can decay off a human face within a month if a body is left outside. However, this chap found in a Danish peat bog looks pretty fresh after more than 2200 years, demonstrating a difference of more than 25,000 (1 month versus 2200 years) in decay rates:
Tollund bog-man. Source: "Tollundmannen" by Sven Rosborn. Licensed under Public Domain via Commons.
Thus, protein and soft tissue decomposition rates vary enormously, depending on the conditions. Some academics have done lab studies of protein degradation using accelerated conditions of high temperature and high acidity, but it is not valid to extrapolate those results to proteins locked in the pores of dinosaur bones. The reality is that we don’t know, with any precision, how fast proteins degrade under the conditions found in dinosaur fossil bones. Thus, it is incorrect to claim that we know that it is impossible for soft tissue to survive in any form for 80 million years. In contrast, the rates of nuclear decomposition of elements have been measured over and over again, and found to be essentially constant. As discussed in the main article, there are a few conditions where nuclear decay can be accelerated, but these conditions are known and predictable, and do not apply to the rock layers in Montana where these dinosaur fossils were found. Thus, it is absurd and insupportable to set aside the radioactive dating of these rock layers because some partly degraded soft tissue has been found in dinosaur fossils from those layers.
I appreciate the work of BioLogos in helping Christians to understand that we can welcome, rather than fear, the findings of modern science. Mary Schweitzer happens to be a devout evangelical Christian, who finds that her view of the Creator has been enriched, not diminished, as she learns more about the complexities of the natural world.