Variability along the frontier: stable carbon and nitrogen isotope ratio analysis of human remains from the Late Roman–Early Byzantine cemetery site of Joan Planells, Ibiza, Spain

Abstract

Carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope analysis of human bone collagen from 38 individuals was undertaken to assess diet at the Late Roman-Early Byzantine (AD 300-700) cemetery site, Joan Planells, in Ibiza, Spain. The results (δ 13 C=-18.7±0.5‰ and δ 15 N=10.1±1.3‰) that the diet of this population was derived predominantly from C 3 terrestrial resources; plant foods were likely dietary staples along with meat and/or dairy produce comprising an important component of diet. Variation in stable isotope ratio values suggest individual differences in diet. Two individuals, both males, are statistical outliers with distinctive δ 15 N values (14.4‰ and 14.8‰) that point to significant consumption of marine resources. Females, on average, have higher δ 13 C values than males. The parsimonious explanation for this observation is the greater inclusion of C 4 resources such as millet in the diets of females. Comparison of the diet of the Joan Planells population with other Late Roman period sites on the Hispanic mainland and other parts of the Mediterranean region suggests that populations may have been responding to a combination of socio-political and environmental factors that could have included Roman influence of food consumptive practices in some of these distant locales.

The effect of diet and sociopolitical change on physiological stress and behavior in lateRoman‐EarlyByzantine (300–700AD) and Islamic (902–1,235AD) populations from Ibiza, Spain

“…Islamic migration is associated with greater consumption of C 4 crops such as millet, sorghum, and sugarcane (Adamson, 2004; Butzer, Mateu, Butzer, & Kraus, 1985; Glick, 2005; Peña‐Chocarro et al, 2019). Isotopic studies confirm greater consumption of C 4 crops in Islamic Ibizan populations (Alaica et al, 2019; Dury et al, 2018; Fuller et al, 2010; Nehlich et al, 2012; Peña‐Chocarro et al, 2019; Pickard et al, 2017). However, the greater isotopic diversity of Islamic individuals may also reflect migration, because isotopic signatures of certain individuals may reflect migration from locations where cultivation of C 4 crops was more extensive (Alexander et al, 2019; Dury et al, 2018; Fuller et al, 2010; Pickard et al, 2017).…”

“…It remains unclear whether altered agricultural practices, changing climate, or influx of new populations with different dietary habits are responsible for increased dependence on C 4 crops in Late/ post‐Roman contexts. Similarly, analysis of Late Roman/ Early Byzantine populations from Ibiza tentatively suggests a small but significant consumption of C 4 cereals (Alaica et al, 2019). Thus, taken together, studies of other Iberian and Mediterranean populations suggest that Ibizan diachronic trends in diet generally follow those seen on mainland Spain.…”

“…This study focuses on the relationship between diet, stress, and behavior. Previous isotopic studies of diet have demonstrated diachronic change and inter‐individual variability in diet throughout the Late Roman‐Early Byzantine (LREB) and the Medieval Islamic period (Alaica et al, 2019; Alexander, Gutiérrez, Millard, Richards, & Gerrard, 2019; Dury et al, 2018; Fuller, Márquez‐Grant, & Richards, 2010; Márquez‐Grant, Fuller, & Richards, 2003; Nehlich, Fuller, Márquez‐Grant, & Richards, 2012; Pickard et al, 2017). Other lines of evidence also suggest political, economic, and cultural change across these periods (Costa, 2019c; Ferrer Abárzuza, 2019a; Gurrea & Martín, 2000; Ramon, 1986).…”

“…It is in fact, Ibiza that yielded one of the first Spanish studies in isotope analysis to reconstruct diet (Márquez‐Grant et al, 2003), with previous studies particularly focusing on trace element analysis (e.g., García & Subirà, 2001; Subirà & Malgosa, 1992). Prior studies of Ibizan diet based on δ 13 C and δ 15 N stable isotopes of bone collagen indicate that, from the Roman to the Islamic period, Ibizan diet predominantly consisted of C 3 cereal crops (e.g., wheat, barley, and, in the Islamic period, rice) (Alaica et al, 2019; Fuller et al, 2010; Nehlich et al, 2012). Supporting this interpretation, historical sources, archeological remains (e.g., plows, mills, terraced lands) and archaeobotany identify cereal crops such as wheat and barley as main dietary staples from the Late Roman to the Islamic period (Adamson, 2004; Alonso, 2005; Dalby & Granger, 2012; García‐Sánchez, 2002; Garnsey, 1999; Peña‐Chocarro et al, 2019; Salas‐Salvadó, Huetos‐Solano, García‐Lorda, & Bulló, 2006; Watson, 1983).…”

“…Given the terrestrial isotope signatures of Ibiza populations, seafood appears to have been a minor component of Ibizan diet (Alaica et al, 2019; Dury et al, 2018; Fuller et al, 2010; Pickard et al, 2017). Still, given the proximity of the ocean, individuals likely consumed some fish, which may have influenced habitual loading patterns.…”