Reconstruction of ancient diet using stable isotope analysis of human soft tissue remains

Abstract

The stable isotopic analysis of the ancient human and animal tissues has become a well-established method that used in reconstructing the paleodiet, as it provides a chemical evidence of the diet and could estimate the relative proportions of food resources consumed by human populations. Since 1970s, the isotopic signature of the body tissue protein, particularly bone collagen, has been shown to reflect that of the diet where, the carbon isotope signature could differentiate between the two major types of plants (C3 vs. C4 photosynthetic plants) in the diet, while the nitrogen isotope signature could distinguish animal vs. plant protein. Thus, from the carbon and nitrogen isotope signatures, inferences about the protein sources in a person’s diet could be made. The most popular tissue protein that has been used in the stable isotope analysis to infer past diet is the bone collagen as it is the most survived body protein. The aim of the thesis is, to reconstruct the diet of Sudanese Nubian natural mummies extracted from two Christian (AD 550–800) cemeteries (R & S) at the site of Kulubnarti. As well as, using microscopic examination in order to examine the state of preservation. The isotopic results of 90 collagen-containing tissue samples (e.g., skin, meninges, periosteum, subcutaneous, tendon, etc……..) and 47 hair samples had been used in the present study. The mummies are curated at the University of Colorado but, sub-samples of tissues from those mummies are stored in the tissue bank of the KNH Centre for Biomedical Egyptology at the University of Manchester, where extraction of the protein was undertaken. Analyses of δ13C and δ15N in protein were done at the Isotope Geosciences Laboratory in Nottinghamshire, U.K., using Continuous Flow-Elemental Analysis-Isotope Ratio Mass Spectrometry (CF-EA-IRMS). Summary 96 The isotopic data of both the collagen-containing tissues and the hair samples indicated that the diet of this Kulubnarti Nubian population included a mix of C3 and C4 plants (predominantly C3) in addition to a relatively small contribution of animal protein from terrestrial sources and no aquatic protein sources. A significant difference was found regarding the δ13C values between the two cemeteries (S & R) in both the collagen-containing tissues and the hair samples which may indicate a diet enriched in 13C (more C4 plants) in the individuals buried in the Kulubnarti R cemetery. The non-significant difference in the δ15N values which was found between the two cemeteries may indicate the consumption of nearly the same proportion of animal protein in the diet. Although the δ13C and δ15N values from bone collagen of the same material showed significant differences between age groups, the soft tissue samples did not show any significant isotopic differences between age and sex categories. The isotopic results from the hair samples, similarly, showed no dietary sex differences, and apart from the significant depleted nitrogen isotopic composition of the S cemetery juveniles, no age differences have been found. Significant differences were found between the different types of the collagen-containing tissue samples in the nitrogen isotopic signatures with meninges and periosteum being the most 15N- enriched tissues, followed by skin, while cartilage was the least 15N-enriched tissue. Hair results showed seasonal variation in the diet of the two cemeteries, varied from dominant C3 plants in the winter to dominant C4 in the summer with a little storage of the non-seasonal grains. The histological examination of the analysed skin samples showed a very good preservation of the collagen fibres.