Aspartic acid racemization dating
In this light, it is interesting to consider what happened in 1974 when some of the major proponents of amino acid dating (Bada et al) decided to analyze the Paleo-Indian skeletal material from Del Mar, California.Their estimated age of 48,000 years before present (BP) "stunned" the archaeological community who generally believed these bones to be less than 10,000 years old.
The rate itself of hydrolysis "depends on the strength of the individual peptide bonds, which in turn is determined by the characteristics of the amino acids on either side of the bond, the presence of water and the temperature."All of these are confounding factors, which, if not known exactly over extended periods of time, would play havoc with any sort of age determinations.Even the process of preparing a specimen for racemic dating can affect the D/L ratio.For example, consider that neither the structure nor the proportion of the amino acids used for dating coral, ostrich eggshell, or snail shells is known. Using"Amino acid dating cannot obtain the age of the material purely from the data itself.Age estimates from the fractions within a bone were consistent if it was well preserved.They concluded that a poorly preserved Pleistocene-age fossil 11,000 years in age would go unrecognised because it would yield a Holocene 14C date.At best three of the four methods put the bones in the Holocene."Because of these problems AAR dating of bone and teeth (teeth in different locations in the same mouth have been shown to have very different AAR ages) is considered to be an extremely unreliable practice even by mainstream scientists.
That is because the porosity of bones makes them more "open" to surrounding environmental influences and leaching.
They did note that there appeared to be a direct relationship between the extent of racemization and the level of preservation of collagen in the bones.
Those samples with the most racemization had the lowest amino acid content and this poor preservation of protein would contribute to anomalous AAR recalculated the AAR dates of the other Paleo-Indian samples.
They all fell within the Holocene but had much larger error estimates than those of the AMS values.
Although Bada claimed consistency between AAR and AMS dates others (Pollard and Heron 1996, p.
The Oxford dates were all between 4,500 and 8,500 years BP and the Arizona dates were between 3,000 and 6,600 years BP.