Multivariate analyses of elemental hair concentrations from a medieval Nubian population

Elemental hair concentrations were obtained from 168 mummified individuals recovered during excavations of cementeries S and R (A.D. 550-1450), at Kulubnarti, Republic of the Sudan (Van Gerven et al., 1981). Concentrations of calcium (Ca), magnesium (Mg), strontium (Sr), manganese (Mn), zinc (Zn), iron (Fe), and copper (Cu) were determined using inductively coupled plasma emission spectrometry (ICP) (Sandford, 1984; Sandford et al., 1983). Following univariate statistical reanalyses of these data (Sandford and Kissling, 1993a, b), we applied principal component analysis and multidimensional scaling to clarify their multivariate structure. Similar underlying associations were revealed in the two cemeteries. The first principal component, consisting of Mg, Ca, Sr, and Mn, may reflect inherent chemical similarities coupled with specific dietary factors (e.g., vegetation intakes) and physiological processes (e.g., bone remodeling). The second principal component, a contrast between Fe and Zn, may be due to their competitive relationship during absorption. The third principal component consists of Cu alone (in cemetery S), and Cu and Fe (in cemetery R), suggesting utilization of animal protein and an underlying synergism between Cu and Fe, respectively. Multidimensional scaling substantiates a three-dimensional model for describing elemental covariation. While interpretation of the first two dimensions was analogous to those of the first two principal components, the third dimension may represent antagonism between pairs of elements during absorption, transport and/or utilization (cemetery R: Cu vs. Zn; cemetery S: Cu vs. Zn, Fe vs. Mn). While these results provide the most persuasive evidence to date that elemental hair concentrations from this population reflect chiefly biogenic processes, isolation of diagenetic and exogenous effects requires further investigation through controlled studies.