STABLE ISOTOPE ANALYSIS OF CHILDHOOD DIET AT 1ST CENTURY B.C./A.D. PETRA, JORDAN

Abstract

Investigations of diet and disease of the population of the Nabataean capital city Petra have found that the adult residents suffered little from chronic infections or malnutrition and had a diet consisting primarily of C3 sources. However, little is known of childhood health and nutrition in the population since few remains of children have been recovered from excavated tombs. This study uses stable carbon and oxygen isotope ratios ([delta]¹³C and [delta]¹⁸O) of dental enamel apatite in first molars (n=31), first premolars (n=20), and second molars (n=29) along with [delta]¹³C of bone apatite (adults n=27, subadults n=4) to explore childhood diet and weaning patterns in a 1st century B.C/A.D. sample from Petra. To assess dietary shifts by age related to weaning, the [delta]¹³Cap bone and enamel results were grouped into five different age ranges based on age of tissue formation: 0.0-2.5 years, 2.6-4.5 years, 4.6-7.0 years, 7.1-19.9 years, and 20.0+ years. The first three categories reflect the ages of dental formation in the first molar (M1), first premolar (PM1), and second molar (M2), respectively. Dietary and trophic level changes, particularly those associated with weaning, should result in a decrease in mean [delta]¹⁸Oap values and [delta]¹⁸ap values should increase between 0.0-2.5 years and 2.6-4.5 years then decrease between 2.6-4.5 and 4.6-7.0 as the adult diet would have been adopted fully after weaning is completed. In the Petra sample, the differences in [delta]¹³Cap between age groups mostly followed the expected pattern with mean [delta]¹³C values increasing from 0.0-2.5 ([mean]=-11.6 [plus-minus] 0.4⁰́/₀₀ and 2.6-4.5 years of age ([mean]=-11.3 [plus-minus] 0.5 ⁰́/₀₀)(Mann-Whitney U Z=2.949, p=0.003), remaining stable through 4.6-7.0 years ([mean]=-11.3 [plus-minus] 1.1⁰/₀₀) and then decreasing dramatically after 7.1 years to fall close to the adult [delta]¹³13Cap value. In addition, the three youngest age categories (i.e., below 7.1 years of age) had values significantly higher than the values of 7.1-19.9 years ([mean]=-12.9 [plus-minus] 0.4⁰́/₀₀ and 20+ years ([mean]=-12.9 [plus-minus] 1.0⁰́/₀₀) age groups (p[less-than]0.001 in each case). Mean [delta]¹⁸Oap values initially decrease between M1 and PM1 before increasing in M2 value, which does not follow the expected pattern. These results may indicate that C4 foods were used as supplementary resources during weaning and that weaning was likely completed after three years of age or a specialized childhood diet was implemented for a period after weaning but before a fully adult diet was adopted. Some confounding factors may include the use of non-human milk during weaning, an early introduction to environmental water, and seasonality in groundwater [delta]¹⁸O values. The influence of immigration on the [delta]¹⁸O values was applicable to only one individual.