With a few important exceptions, living organisms keep all their amino acids in the “L” configuration.
When an organism dies, control over the configuration of the amino acids ceases, and the ratio of D to L moves from a value near 0 towards an equilibrium value near 1, a process called racemization.
This is still a large number of C14 atoms, and they had to come from somewhere!
Amino acid racemization dating of fossil bones
Perhaps there was less C14 produced in the past, which would imply that even the relatively young C14 dates are too old. The C14/C12 ratio of living things and organic matter on the surface of the earth is about the same as in the atmosphere because carbon is constantly exchanged between living things and the atmosphere.
After an organism dies, if it is buried and left undisturbed, the C14 in it gradually decays into nitrogen 14. Thus the ratio of C 14 to C12 in the remains of the organism gradually decreases with time.
It is calibrated by C14 dating, and the ages given by the two methods are in close agreement after such calibration.
In millions of years, there would certainly be roughly equal numbers of D and L forms, so that the ratio of D to L would be one.
Even more, proteins in this tissue retain their structure.
Extraordinary efforts were made to eliminate all contamination from the measuring apparatus.All these results have been reported in the conventional scientific literature. Pieces of fossilized wood in Oligocene, Eocene, Creta- ceous, Jurassic, Triassic, and Permian rock layers supposedly 32–250 million years old all contain meas- urable radiocarbon, equivalent to “ages” of 20,700 to 44,700 years. Similarly, carefully sampled pieces of coal from ten U. coal beds, ranging from Eocene to Pennsylvanian and supposedly 40–320 million years old, all contained similar radiocarbon levels equivalent to “ages” of 48,000 to 50,000 years.Even fossilized ammonite shells found alongside fossilized wood in a Cretaceous layer, supposedly 112–120 million years old, contained measurable radiocarbon equivalent to “ages” of 36,400 to 48,710 years.These results were discussed in a recent Mary Schweitzer’s results shows that essentially all the remaining material in the dinosaur bone is original because she had no trouble finding these young appearing proteins.If there had been contamination, then it would have introduced other substances into the soft tissue.In a 2015 paper in , her group reported isolating fragments of eight other proteins from fossils of dinosaurs and extinct birds, including hemoglobin in blood, the cytoskeletal protein actin, and histones that help package DNA. All amino acids except glycine (the simplest one) are optically active, having a stereocenter at their α-C atom.