Achaeometrical Research in Hungary II., 1988

PROSPECTING and DATING - János CSAPÓ - Zsuzsanna CSAPÓ-KISS - János CSAPÓ JR.: How the amino acids and amino acid racemization can be used and with what limits for age determination of fossil materials in archaeometry

Table 9 Half lives of racemization and epimerization of various amino acids found in Hungarian fossil bone samples Amino acids Half life (year) Histidine 5500 Phenylalanine 8500 Tyrosine 8600 Aspartic acid 13500 Serine 16500 Threonine 17000 Glutamic acid 28500 Alanine 32000 Isoleucine 110000 Leucine 140000 Valine 180000 Known age (Y) was regressed on D/L ratio (Xj) and ln[(l+D/L)/(l-D/L)] (X

2

) for each of four amino acids (Phe, Asp, Ala and He) to produce prediction equations of the form y = a + bX. All eight regression equations produced r^ values greater than 0.99. In each amino acid, r

x x was greater than 0.99 which means that X

2 was simply a coded value of Xj. The standard deviation of deviations from regression (standard error of estimate= s ) can be used to calculate the standard error of an individual estimate as Y.X 2 „ S y 2 /

v „/7//1 + (X-X)

2

/Sum(X-X)

2

) YX with n=number samples used in estimating regression and sum (X-X Y being the sum of squares of deviations from the mean X. The value, S$ was calculated for each regression for two situations (X=X and X=an extreme value). For Phe, Asp and Ala, mean values for D/L were 0.35 to 0.41 and extremes were approximately ± 0.30. Corresponding means for ln(X ) were 0.75 to 0.90 and extremes were ± 0.75. For He, means were 0.16 and 0.32 with corresponding extremes at ± 0.06 and ± 0.12. The two S- values for each amino acid mean and extreme were averaged to produce the following values: Amino acid Extreme Mean Phe 189 329 Asp 226 458 Ala 382 988 lie 311 514 34