Fe and Cu stable isotopes in archeological human bones and their relationship to sex

Abstract

Accurate sex assignment of ancient human remains usually relies on the availability of coxal bones or well-preserved DNA. Iron (Fe) and copper (Cu) stable isotope compositions ((56)Fe/(54)Fe and (65)Cu/(63)Cu, respectively) were recently measured in modern human blood, and an unexpected result was the discovery of a (56)Fe-depletion and a (65)Cu-enrichment in men's blood compared to women's blood. Bones, being pervasively irrigated by blood, are expected to retain the (56)Fe/(54)Fe and (65)Cu/(63)Cu signature of blood, which in turn is useful for determining the sex of ancient bones. Here, we report the (56)Fe/(54)Fe, (65)Cu/(63)Cu, and (66)Zn/(64)Zn ratios from a suite of well-preserved phalanxes (n = 43) belonging to individuals buried in the 17th and 18th centuries at the necropolis of Saint-Laurent de Grenoble, France, and for which the sex was independently estimated from pelvic bone morphology. The metals were purified from the bone matrix by liquid chromatography on ion exchange resin and the isotope compositions were measured by multiple-collector inductively coupled plasma mass spectrometry. The results show that, as expected from literature data on blood, male bone iron is depleted in (56)Fe and enriched in (65)Cu relative to female. No sex difference is found in the (66)Zn/(64)Zn ratios of bone. The concentration and isotopic data show no evidence of soil contamination. Four samples of five (77%) can be assigned their correct sex, a result comparable to sex assignment using Fe and Cu isotopes in blood (81%). Isotopic analysis of metals may therefore represent a valid method of sex assignment applicable to incomplete human remains.

Menopause effect on blood Fe and Cu isotope compositions

“…Iron and Cu isotopic changes in women's bones are expected to occur after 60 years old given an age at menopause of 50 years old. In our study on the population buried during the XVII and XVIII in Saint-Laurent de Grenoble (France), age-at-death assessment of the population gave large range of variations and we could not clearly identify whether women died over 60 years old or not (Jaouen et al, 2012). The oldest female age group, containing women dead over 45 years old did not show significant isotopic sex differences relative to the younger group.…”

“…We recently demonstrated that Fe and Cu isotope compositions in bones reflect patterns observed in blood (Jaouen et al, 2012), which could have consequences for the use of Fe and Cu isotope as a sex indicator for past populations. However, one must remember that bone turnover is about 10 years for human, increases with aging (Fatayerji and Eastell, 1999) and is slower in the cortical part of bones (Sealy et al, 1995).…”

“…Such an isotopic sex effect has also been described for copper (Cu) isotopes, but in this case, Cu in women's blood is isotopically lighter relative to that of men (Albarède et al, 2011). We further demonstrated that the blood sex isotopic differences were recorded in bones, which could bring additional information for sex assessment for incomplete past human remains (Jaouen et al, 2012).…”

Natural variations of copper and sulfur stable isotopes in blood of hepatocellular carcinoma patients

“…Cu ratio, expressed in delta units (Method), varies between organs from −1‰ in liver to +1‰ in kidney (6) (for comparison, this ratio ranges from −3‰ to +2.5‰ in terrestrial materials). In humans, the 65 Cu/ 63 Cu ratio in blood and bone differs between men and women (7,8), partly because a sizeable proportion of the women's blood copper comes from the liver to balance menstrual losses (9,10). The body 65 Cu/ 63 Cu ratio varies according to that of diet (11) and also seems to be age dependent (12).…”

Cu Isotopic Composition in Surface Environments and in Biological Systems: A Critical Review

“…More interestingly, B-type men erythrocytes could fractionate Cu to a larger extent than all the other blood types, and light Cu was mainly enriched in blood and lymphatic circulation rather than in erythrocytes [105]. Jaouen et al [81] found that δ 65 Cu values in human blood decreased with age, and Cu isotope ratios in the Yakut’s blood were significantly lighter than those in blood of European and Japanese populations. In an archeological human bone study, the male’s bones exhibited heavier Cu isotopes than the females’ bones, implying Cu isotopes could be used as a valid tool to distinguish sexes of incomplete human remains [103].…”