## 3 Results and Discussion
### Diet Reconstruction
These values must be adjusted by one trophic level, \(1\%\) for \(\xi^{13}\)C [34,78] and \(3\%\) for \(\xi^{15}\)N [39], in order to represent the diet. We observed that human collagen samples are enriched in both \(\xi^{13}\)C and \(\xi^{15}\)N isotopic values in comparison to herbivores. The mean bone collagen human \(\xi^{13}\)C value is \(3\%\) higher than the mean faunal value, while the mean bone collagen human \(\xi^{15}\)N value is \(3\)-\(4\%\) higher than the mean faunal one. Thus, Figure 1 clearly shows that the vast majority of humans have bone collagen \(\xi^{15}\)N values \(1\)-\(5\%\) higher than those of terrestrial herbivores (\(3\)-\(6\%\)), exhibiting the trophic level effect and demonstrating the importance of terrestrial C3 sources in the diet. In addition, we observed that the results from Agras (EIA) were in good agreement with the ones of Edessa (Roman) (\(t\)-test for \(\xi^{13}\)C: \(t=0.94\), \(p=0.36\) and for \(\xi^{15}\)N: \(t=1.92\), \(p=0.08\)), as well as the ones of Alexandreia (recent) (\(t\)-test for \(\xi^{13}\)C: \(t=1.62\), \(p=0.13\) and for \(\xi^{15}\)N: \(t=0.08\), \(p=0.93\)). The much enriched \(\xi^{13}\)C isotopic values, together with the enriched \(\xi^{15}\)N values, indicate a combined terrestrial diet of mainly C3 and secondary C4 diet, like millet, in combination with freshwater fish consumption. Probably, the C4 diet was mainly introduced by the consumption of animals fed with millet and secondary as a direct food source. The elevated nitrogen value, \(8.8\%\), indicates that legumes were not a significant part of the diet as their \(\xi^{15}\)N values range between \(0\%\) and \(2\%\)[79]. Additionally, their isotopic values do not reflect a marine diet, a result consistent with the site location, i.e., far from the sea. Moreover, the sample T24-KT, which exhibits the lowest \(\xi^{15}\)N value, \(6\%\), reflects a diet of C3 and C4 with a minimal animal protein contribution. On the contrary, sample T6b has a very negative \(\xi^{13}\)C isotopic value, \(-20.5\%\), which indicates no  
Figure 2: \(\xi^{13}\)C\({}_{\text{col}}\) (v-PDB) and \(\xi^{15}\)N\({}_{\text{col}}\) (v-AIR) of human bone collagen of Agras, Edessa [3] and Alexandreia [2] in comparison with domesticated animals [2,11,58] (C3 plants, terrestrial animals) and freshwater and marines fish. C4 contribution to the diet. Both of these individuals were buried with their arms bent at the elbow and raised to the shoulder, which is an uncommon posture and may have had some ritual significance [59]. Taking into consideration the geographical location (close to Vegoritida Lake and Edessaios River), it is possible that the population under study consumed significant quantities of freshwater fish. In order to validate this assumption, we analyzed the \(\xi^{13}\)C\({}_{\text{ap}}\) isotope from bone apatite, which reflects the total diet [33], while the difference between \(\xi^{13}\)C\({}_{\text{col}}\) and \(\xi^{13}\)C\({}_{\text{ap}}\) is an indicator of the protein source [34]. In our results (Table 1), these differences ranged from 4.3% to 5.6% with a mean value of 4.9%, which is greater than 4.4%, the threshold above which the protein consumption is mainly derived from terrestrial sources [80,81]. The individuals T4b and T50b had \(\Delta\)C\({}_{\text{ap-col}}\) values of 4.5% and 3.8% (Table 1), respectively, so it seems that there was freshwater fish protein in their diet. On the contrary, individuals T6b and T33b had greater differences in \(\Delta\)C\({}_{\text{ap-col}}\), 5.6% and 5.1% (Table 1), which indicates terrestrial food sources. In Table 2 we present the results from the statistical packages IsoSource and Fruits.