Isotopic evidence for breastfeeding and possible adult dietary differences from Late/Sub-Roman Britain

Historical documents indicate that breastfeeding and weaning practices have fluctuated in England through history. In order to obtain evidence for general breastfeeding patterns in Late/Sub-Roman Britain, stable carbon and nitrogen isotope values were measured in juvenile and adult skeletons (n = 87) from the cemetery of Queenford Farm, Dorchester-on-Thames, Oxfordshire. As the site contained few individuals between 0-1.5 years of age, it was not possible to determine the initial timing for the introduction of weaning foods. Between ages 2-4 years, the mean +/- SD delta(13)C results (-20.2 +/- 0.3 per thousand) are significantly more negative (t = -4.03, P < 0.001) compared to adult females (-19.7 +/- 0.3 per thousand). This is interpreted as evidence of a different diet being fed to children during weaning. After age 2, the delta(15)N values gradually decline, indicating complete cessation of breastfeeding by 3-4 years. Among adults, stature (males = 1.68 +/- 0.06 m; females = 1.58 +/- 0.07 m) and sexual dimorphism (106) were low, suggesting that the population was possibly under environmental stress. The delta(13)C results for adults are similar, but females show a small but statistically significantly (t = -2.86, P < 0.01) lower mean delta(15)N value (9.9 +/- 0.9 per thousand) compared to males (10.6 +/- 0.5 per thousand). These lower female delta(15)N values possibly reflect the different physiology of the sexes (pregnancy and/or lactation) or the reduced consumption of animal/fish protein by women, and this may have been influenced by individual preference, family needs, or societal values of the era.     

Processing of prehistoric bones for isotopic analysis and the meaning of collagen C/N ratios in the assessment of diagenetic effects

Diagenetic shifts in the isotopic composition of collagen in prehistoric bones still remain a big problem in the reconstruction of ancient diets by stable carbon and nitrogen isotope analysis. Recently,DeNiro (1985) suggested the measurement of bone collagen C/N ratios as a means of estimating substantial alterations of stable isotope ratios. Bones with collagen C/N ratios lying within a range between 2.9 and 3.6 should have isotopic properties quite close to thein vivo conditions. It can be demonstrated that the C/N ratios are varying considerably with the duration of acid hydrolyzation of the bone samples. Even small changes of the hydrolyzation time cause shifts in the C/N ratios large enought to produce values far outside the range worked out byDeNiro. Besides, our experiments led us to recommend a hydrolyzation at reducing conditions.     

Conformity in diversity? Isotopic investigations of infant feeding practices in two iron age populations from Southern Öland,Sweden

This article presents the results of a study of infant diet at two Iron Age sites on the island of Öland, Sweden. The cemetery at Bjärby contained a large number of subadults who had survived the earliest years of life, whereas most individuals at Triberga had died by 6 months of age. To investigate whether differences in infant feeding could explain the different mortality rates, the carbon, nitrogen, and sulfur stable isotope ratios of bone and tooth dentin collagen from the two sites were analyzed. Twenty‐two samples from Triberga and 102 from Bjärby yielded data that could be included in the carbon and nitrogen analysis. Twelve samples from Triberga and 42 from Bjärby were included in the sulfur analysis. The results for carbon (δ¹³C: Triberga X = –18.8, s.d. = 1.1; Bjärby X = –19.8, s.d. = 0.4), nitrogen (δ¹⁵N: Triberga X = 12.9, s.d. = 1.5; Bjärby X = 13.4, s.d. = 1.4), and sulfur (δ³⁴S: Triberga X = 8.1, s.d. = 1.1; Bjärby X = 5.8, s.d. = 1.3) suggest that diet was broadly similar at both sites and based on terrestrial resources. At Bjärby, females and high‐status individuals consumed higher‐trophic level protein than other males from early childhood onward. There was some indication that the contribution of marine resources to the diet may also have differed between the sexes at Triberga. No consistent differences in breast milk intake were observed between the two sites, but there was substantial variation at each. This variation may reflect an influence of gender and social status on infant feeding decisions. Am J Phys Anthropol 149:217–230, 2012. © 2012 Wiley Periodicals, Inc.     

Using a nitrogen and oxygen isotopic approach to identify nitrate sources and cycling in the Wei River of northwestern China

The Wei River is the largest tributary of the Yellow River in China. To understand the sources and cycling of nitrate in the Wei River, we determined the concentrations and nitrogen and oxygen isotopic values of nitrate from water samples. Our results revealed that NO₃^?-N dominated the inorganic N and ranged from 0.1 to 8.8 mg/L (averaging 3.3 mg/L). Although this NO₃^?-N concentration does not exceed the World Health Organization's drinking water standard of 10 mg/L, the NO₃^?-N content of most water samples exceeded 3 mg/L, indicating poor water quality. The NO₃^?-N concentrations and δ¹⁵N-NO₃^? values demonstrate that there are significant differences in the spatial distribution of nitrogen between the tributaries and the main stream of the Wei River. In addition, a negative linear relationship (r² = 0.63) between NO₃^?-N concentrations and δ¹⁸O-NO₃^? values suggests mixing between two distinct sources (fertilizer and manure or sewage). Furthermore, we infer that the main source of nitrate is not manure or sewage itself, but rather the nitrification of NH₄⁺ in manure and sewage. Finally, no obvious denitrification processes were observed. These results expand our understanding of sewage as a major source of nitrate to the Wei River, emphasizing the role of nitrification.     

Insights from stable light isotopes on enamel defects and weaning in Pliocene herbivores

A high prevalence of enamel hypoplasia in several herbivores from the early Pliocene Langebaanweg locality, South Africa, indicates general systemic stress during the growing years of life. The presence of several linear enamel hypoplasias per tooth crown in many teeth further suggest that these stress events may be episodic. The δ¹⁸O values along tooth crowns of mandibular second molars ofSivatherium hendeyi (Artiodactyla, Giraffidae) were used to investigate the cause of the stress events in this tooth type. Results show that weaning in this fossil giraffid occurred at a similar ontogenetic age to that in extant giraffes, and that the observed enamel hypoplasia towards the base of this tooth type manifested post-weaning. Further, high-resolution oxygen isotope analyses acrossS. hendeyi third molars suggest that the entire development of defective tooth crowns occurred under conditions of increased aridity in which the cool, rainy part of the seasonal cycle was missing. The high prevalence of this defect in many herbivores suggests that climatic conditions were not favourable. This study reiterates the value of stable isotope analyses in determining both the behaviour of fossil animals and the environmental conditions that prevailed during tooth development.