## 3 Results
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **IRSF** & **FWHM\({}_{603}\)** & **C/P** & **MM** & **Amidel/PO\({}_{4}\)** \\ \hline H–41 & 2.53 \(\pm\) 0.226 & 23.5 \(\pm\) 0.85 & 0.136 \(\pm\) 0.007 & 2.96 \(\pm\) 0.11 & 0.032 \(\pm\) 0.005 \\ H–669 & 2.57 \(\pm\) 0.165 & 25.1 \(\pm\) 0.58 & 0.206 \(\pm\) 0.005 & 3.07 \(\pm\) 0.15 & 0.087 \(\pm\) 0.006 \\ H–715 & 2.46 \(\pm\) 0.198 & 24.7 \(\pm\) 0.60 & 0.196 \(\pm\) 0.008 & 2.56 \(\pm\) 0.25 & 0.078 \(\pm\) 0.004 \\ H–716 & 3.00 \(\pm\) 0.225 & 17.6 \(\pm\) 0.92 & 0.043 \(\pm\) 0.008 & 3.69 \(\pm\) 0.22 & 0.018 \(\pm\) 0.005 \\ H–914 & 2.87 \(\pm\) 0.154 & 25.6 \(\pm\) 0.67 & 0.198 \(\pm\) 0.007 & 2.67 \(\pm\) 0.17 & 0.058 \(\pm\) 0.005 \\ H–954 & 2.38 \(\pm\) 0.158 & 24.1 \(\pm\) 0.56 & 0.209 \(\pm\) 0.010 & 2.88 \(\pm\) 0.14 & 0.084 \(\pm\) 0.005 \\ H–976 & 2.47 \(\pm\) 0.151 & 18.0 \(\pm\) 0.67 & 0.105 \(\pm\) 0.009 & 2.15 \(\pm\) 0.14 & 0.022 \(\pm\) 0.005 \\ H–1191 & 2.42 \(\pm\) 0.215 & 20.8 \(\pm\) 0.79 & 0.135 \(\pm\) 0.008 & 2.66 \(\pm\) 0.19 & 0.039 \(\pm\) 0.004 \\ H–1226 & 2.67 \(\pm\) 0.169 & 18.9 \(\pm\) 0.73 & 0.174 \(\pm\) 0.009 & 3.25 \(\pm\) 0.17 & 0.061 \(\pm\) 0.006 \\ A–2 & 3.83 \(\pm\) 0.326 & 19.7 \(\pm\) 0.83 & 0.124 \(\pm\) 0.008 & 2.42 \(\pm\) 0.25 & 0.053 \(\pm\) 0.002 \\ A–6 & 3.40 \(\pm\) 0.325 & 18.6 \(\pm\) 0.95 & 0.125 \(\pm\) 0.008 & 2.37 \(\pm\) 0.25 & 0.049 \(\pm\) 0.002 \\ A–106 & 3.47 \(\pm\) 0.201 & 20.0 \(\pm\) 1.10 & 0.149 \(\pm\) 0.007 & 2.24 \(\pm\) 0.25 & 0.053 \(\pm\) 0.004 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Diagenetic parameters calculated by ATR–FTIR analysis of human and animal bone samples collected at the Fewet oasis: IRSF, FWHM\({}_{603}\), C/P, MM, and amide I/PO\({}_{4}\). Data are reported as mean \(\pm\) S.D. Figure 3: PCA scores plot of bones’ spectral parameters; the percentages of variance explained by PC1 and PC2 are reported in brackets. The statistical analysis of the diagenetic parameters reported in Table 2 is shown in Figure 4. The following considerations can be drawn: (i) with regards to the amide I/PO\({}_{4}\) ratio, the lowest values were displayed by H-716M and H-976M samples, which also showed the best segregation in the PCA scores plot, whereas samples H-669F, H-715F, and H-954F exhibited the highest ones; (ii) a similar trend was displayed with regards to the C/P index; (iii) concerning the MM index, the highest and lowest values were displayed respectively by samples H-716M and H-976M; (iv) sample H-716M also exhibited the lowest FWHM\({}_{603}\) and the highest IRSF values; (v) data from the modern ruminants showed intermediate values. All these findings suggest that H-716M and H-976M were characterized by spectral features that were almost different from all the other samples. In particular, in both of these samples, the organic matrix was highly degraded and only a low amount of carbonate ions was present. Moreover, sample H-716M was characterized by a major amount of crystalline hydroxyapatite, as suggested by the low value of FWHM\({}_{603}\) and by the high values of IRSF and MM. No correlation was found between the C/P and MM indexes among all the groups (Figure 5), which indicated that the level of hydroxyapatite recrystallization of the Fewet samples was independent of their C/P ratio. Finally, a multinomial logistic regression was performed to investigate the real and numerical correlation between the above defined spectral parameters and specific categorical dependent variables related to humans, such as the presumptive age at death, sex, chronological attribution, and the burial area. A correlation was only found with the burial area (BA1-3 categories for humans and ENV category for animals) (Figure 6). In particular, with regards to the amide I/PO\({}_{4}\) ratio, the probability associated with BA1 and BA2 reached its maximum level (0.4) at a value of ca.