Question:

I have a question about reports in recent years (in technical, and in consumer oriented publications) of proteins, hemoglobin, collagen and various soft-tissue samples being found in various dinosaur fossils.  Are these kinds of compounds able to survive for millions of years within a fossil? Seems counter-intuitive….  I have long been satisfied the earth and universe are quite old,,,,but I’m not a geologist, nor biochemist, and am puzzled how these kinds of finds fit with millions of yrs?   Thank you for any clarity if you have time.

References:   1. Smithsonian Mag, May 2006, Helen Fields, “Dinosaur Shocker”, about RBCs and soft tissue, proteins in T.Rex fossils.   2. Schweitzer & Wittmeyer, “Soft-tissue preservation from Cretaceous to present”, proceedings from the Royal Society B, 2007, p183-197.  3.  Nielsen-Marsch, “Biomolecules in fossil remains”, in The Biochemist, June 2002, p12-14.

Answer:

I am not aware of the specific decay rates for individual molecular decompositions, so I cannot give real numbers.  However, completely dessicated (dried) protein molecules could probably last literally for millions of years.  By this time, the materials would be sufficiently decomposed to give only a rather vague idea of the initial structure, but some basic information could presumably be extracted.

DNA would, on the other hand, almost certainly be completely degraded, even if fully dessicated, within hundreds or at most several thousands of years.  I predict that intact DNA of dinosaurs will not be discovered no matter how hard we look.

You might want to check into what they mean by “Soft-tissue preservation.”  The words soft-tissue can be a bit misleading. What this probably means is actual molecules, but not anything like flesh, with its vast array of large, complex molecules.  This would be smaller organic molecules rather than fully lost organic material which has been replaced by crystalized inorganic matter which is typical of most fossils.  In the “Dinosaur Shocker” article the actual molecule discovered was heme, which is a fairly small organic molecule.  It is not all that surprising that this molecule would survive millions of years–easier to imagine than intact polypeptides/proteins and much easier to imagine than intact DNA.

The 2002 article gives real numbers, but this author suggests hundreds of thousands of years as an absolute max for DNA to be preserved in measurable amounts and in the millions for very stable kinds of protein such as collagen.  I believe that these are reasonable numbers, although nearly all fossils will not have such materials.  This would be a very rare and fortunate set of circumstances.

The Smithsonian article notes that young earthers have used this kind of evidence to “prove” their point of view.  They say that finding “soft tissue” in dinosaur fossils is evidence that these bones are only a few thousand years old.  However, this is a non-starter, as far as I can see, as we will need to know what kind of molecule has been preserved and under what circumstances.  For example, the fact that a tissue-shaped preserved crystalline chunk still being red due to the heme molecule, even for tens of millions of years, is not beyond reason, and certainly is not evidence that such a fossil is only a few thousand years old.  The discovery of preserved collagen or heme inside a fossilized remain is really awesome, but it is perfectly reasonable under absolutely ideal conditions, such as in an effective sealed capsule inside a fossilized bone.  It certainly is not evidence that dinosaurs lived only a few thousand years ago.

John Oakes