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.
An object is said to have chirality if it is not possible to make it into a mirror-image of itself by turning it round.
Its main weakness is the fact that it is a molecular- rather than an atomic-scale reaction (cf.
radionuclide decay), and as a consequence the rate is sensitive to temperature.
So the process of racemization looks like a good candidate for one of nature's clocks.
All this is not to say that the reader should dismiss out of hand results obtained by amino acid dating; but it can be trusted only when the people applying it have taken care to ensure that they are using it in a context in which it is known to work.
In early papers, before geologists and archaeologists had learned the pitfalls associated with amino acid dating, inaccurate dates were presented with much more confidence than they deserved, and such papers should not be relied on.
Amino acid racemization (AAR) dating is a geochronological technique with a very long history.
Over the past 60 years, many researchers and laboratories around the world have been involved with the development of the method and its application to diverse environments.
Its time depth and applicability to a wide range of substrates are the main strengths of this method.