Where has amino acid racemization dating been used
Beatrice uses ostrich egg shells to date early modern human sites in South Africa. Amino acid geochronology is a relative dating technique able to span the whole Quaternary. It can be applied to a range of common materials which are directly related to the human occupation of an archaeological site, for example mollusc shells and ostrich eggshells. These are also preserved in sediments which accumulated as a response to global climatic pulses, during the Pleistocene and beyond. Therefore, amino acid geochronology has the potential to be widely applicable to the chronology of human evolution, as well as to the geological record. Racemisation it is a post-mortem spontaneous reaction, involving the interconversion between two different forms of a single amino acid, the D- and L-forms these are chemically identical but differ in the spatial configuration of their atoms.
In chemistry , racemization is a conversion, by heat or by chemical reaction, of an optically active compound into a racemic optically inactive form. Half of the optically active substance becomes its mirror image enantiomer referred as racemic mixtures i. If the racemization results in a mixture where the D and L enantiomers are present in equal quantities, the resulting sample is described as a racemic mixture or a racemate. The two forms, which are non-superposable when rotated in 3-dimensional space, are said to be enantiomers. The notation is not to be confused with D and L naming of molecules which refers to the similarity in structure to D -glyceraldehyde and L -glyceraldehyde. Also, R - and S - refer to the chemical structure of the molecule based on Cahn—Ingold—Prelog priority rules of naming rather than rotation of light.
Dating of Holocene sediments in shallow coastal areas of the German North Sea by conventional techniques is commonly problematic. In particular the marine reservoir effect of radiocarbon means that radiocarbon dating cannot be applied to sediments younger than about years. Amino acid racemization dating AAR is a viable alternative for dating young sediments.
Amino acid dating is a dating technique      used to estimate the age of a specimen in paleobiology , molecular paleontology , archaeology , forensic science , taphonomy , sedimentary geology and other fields. This technique relates changes in amino acid molecules to the time elapsed since they were formed. All biological tissues contain amino acids. This means that the amino acid can have two different configurations, "D" or "L" which are mirror images of each other. With a few important exceptions, living organisms keep all their amino acids in the "L" configuration.