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:
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.