Due to the strong dependency of racemization rates on temperature, water concentration, and alkalinity, uncertainties regarding conditions of preservation can leave amino-acid-based age relationships among even similar fossils open to question.At the present time there is insufficient knowledge concerning the effective average racemization rate in a fossil as a function of time to justify dependence on D/L ratios for a quantitative determination of age.Amino acid racemization (or ) in fossils is interpreted in terms of relative ages.If the reaction rate can be calibrated using an independently dated nearby site with similar thermal history, absolute dates can be inferred through calibration.The survival of amino acids in fossils from the Paleozoic era and the trend for the apparent racemization rate constant to decrease with conventional fossil age assignment raise a serious question concerning the accuracy with which radioisotope age data have been used to represent the real-time history of fossils.The instability of the twenty amino acids which are the building blocks of proteins provides a possible means for determining the ages of fossils.In this article we shall discuss the principles behind amino acid dating (also known as racemization dating); we shall discuss how it ought to work, and why it often doesn't.
So when an organism dies, its amino acids are left-handed.
Its time depth and applicability to a wide range of substrates are the main strengths of this method.
Its main weakness is the fact that it is a molecular- rather than an atomic-scale reaction (cf.
The concentration of aspartic acid remained almost constant with age both in inter- and intra-crystalline proteins, and its contribution to the total amino acid content increased with age at the expense of other amino acids such as glutamic acid, serine, glycine and alanine.
Temperature is thought to play a key role in the amino acid racemisation of and could explain why in the localities belonging to the Gravettian and Solutrean period, which formed during relatively cold conditions, D/L values were similar to those detected in shells from sites formed during the Magdalenian.
The main protein leaching from the inter-crystalline fraction occurred within the first 6000 yr after the death of the organism.