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.     

Improving stable isotopic interpretations made from human hair through reduction of growth cycle error

A recent trend in stable isotopic analysis involves the reconstruction of short-term variations in diet using hair segments. However, bulk hair samples typically contain a growth cycle error, which may conceal or confound the most recently incorporated isotopic information. It is assumed that, at any given time, ～85-90% of scalp hairs are actively growing, while the remaining 10-15% have transitioned into a resting or inactive phase, which lasts up to 4 months before hairs are shed. This study uses growth phase to determine the effects of age, sex, and health status on carbon and nitrogen isotopic ratios of hair analyzed in sequential segments. For this study, we selected archaeological hair samples from 10 individuals from Dakhleh Oasis, Egypt. Isotopic analyses of actively growing hair segments were compared to those for mixed growth phase segments from each individual. These data demonstrate the presence of growth cycle error and show that an understanding of structural-functional relationships is essential for interpreting normal versus pathological changes in hair follicle and fiber production. In situations where diet change and mobility produce variations in an individual's isotopic composition, elimination of positional-temporal error in sequential segment hair analyses can facilitate greater understanding of intraindividual metabolic reactions and changes in hair growth cycles. Phase identification may aid in determining the presence of pathological conditions in individuals, especially in those lacking skeletal indications, and provide a more precise estimation of seasonal dietary patterns, access to changing food resources, and metabolic equilibration to a new locality.     

Using stable isotope analysis to examine the effect of economic change on breastfeeding practices in Spitalfields, London, UK

Breastfeeding patterns were subject to a number of fads in 18th and 19th century Britain. Feeding infants by hand, rather than maternal breastfeeding or wet-nursing, became more prevalent among both the wealthy and poor. Substitute foods may have been a convenient alternative for mothers employed away from the household. This study used stable isotope ratio analysis to examine the weaning schedule in the 18th and 19th century skeletal assemblage from Spitalfields, London, UK. Analysis of 72 juvenile ribs revealed δ(15) N elevations of 2-3‰ above the adult mean for individuals up to the age of two, while elevations of 1-2‰ were observed in δ(13) C for the first year of life. This suggests that the introduction of solid foods took place before the end of the first year, and that breastfeeding had entirely ceased by 2 years of age. The age at death of many of these infants is known from historical records, and can be used to pinpoint the amount of time required for the breast milk signal to be observed in the stable isotope ratios of rib collagen. Results show that a δ(15) N elevation can be detected in the ribs of individuals who died as young as 5-6 weeks. Not all individuals at Spitalfields were breastfed, and there may not have been a single uniformly practiced weaning scheme. There is, however, more evidence for prolonged breastfeeding during the 19th century than the 18th century.     

Maritime adaptations and dietary variation in prehistoric Western Alaska: Stable isotope analysis of permafrost‐preserved human hair

The reconstruction of diet and subsistence strategies is integral in understanding early human colonizations and cultural adaptations, especially in the Arctic—one of the last areas of North America to be permanently inhabited. However, evidence for early subsistence practices in Western Alaska varies, particularly with regards to the emergence, importance, and intensity of sea mammal hunting. Here, we present stable carbon and nitrogen isotope data from permafrost‐preserved human hair from two new prehistoric sites in Western Alaska, providing a direct measure of diet. The isotope evidence indicates a heavy reliance on sea mammal protein among the earlier Norton‐period group (1,750 ± 40 cal BP), confirming that the complex hunting technologies required to intensively exploit these animals were most likely already in place in this region by at least the beginning of 1st millennium AD. In contrast, analysis of the more recent Thule‐period hair samples (650 ± 40 cal BP; 570 ± 30 cal BP) reveals a more mixed diet, including terrestrial animal protein. Sequential isotope analysis of two longer human hair locks indicates seasonal differences in diet in a single Norton‐period individual but demonstrates little dietary variation in a Thule‐period individual. These analyses provide direct evidence for dietary differences among Alaska's early Eskimo groups and confirm the antiquity of specialized sea mammal hunting and procurement technologies. The results of this study have implications for our understanding of human adaptation to maritime and high‐latitude environments, and the geographical and temporal complexity in early Arctic subsistence. Am J Phys Anthropol 151:448–461, 2013.© 2013 Wiley Periodicals, Inc.     

Isotopic studies of the diet of the people of the coast of British Columbia

In 1982, Chisholm et al. used δ¹³C data for human burials from shell midden sites widely distributed on the coast of British Columbia (BC) to show the extreme dependence of these individuals on high trophic level marine consumers, principally salmon and marine mammals. Here, we present previously unpublished analyses of δ¹⁵N for some of the same individuals as well as δ¹³C data for additional individuals. Nitrogen isotope data show that the diet was dominated by high trophic level marine fauna including carnivorous fish and marine mammals. Although most burials were found in shell middens, marine mollusks made up of only a minor component of diet. The data for δ¹³C demonstrate that terrestrial faunal foods are undetectable in the diet of the majority of individuals, and seldom constitute more than 10% of the dietary protein of individuals living on the coast although terrestrial fauna were widely available as a potential source of protein. This dietary pattern of exclusion of land‐based animals from their diet persisted for almost 6,000 years along a wide expanse of coastline. In contrast, people from the BC interior (100 km or more from the coast) consumed a mixed diet of terrestrial and marine foods including spawning salmon. Am J Phys Anthropol 155:460–468, 2014. © 2014 Wiley Periodicals, Inc.     

Intraskeletal isotopic compositions (δ13C, δ15N) of bone collagen: Nonpathological and pathological variation

Paleodiet research traditionally interprets differences in collagen isotopic compositions (δ¹³C, δ¹⁵N) as indicators of dietary distinction even though physiological processes likely play some role in creating variation. This research investigates the degree to which bone collagen δ¹³C and δ¹⁵N values normally vary within the skeleton and examines the influence of several diseases common to ancient populations on these isotopic compositions. The samples derive from two medieval German cemeteries and one Swiss reference collection and include examples of metabolic disease (rickets/osteomalacia), degenerative joint disease (osteoarthritis), trauma (fracture), infection (osteomyelitis), and inflammation (periostitis). A separate subset of visibly nonpathological skeletal elements from the German collections established normal intraindividual variation. For each disease type, tests compared bone lesion samples to those near and distant to the lesions sites. Results show that normal (nonpathological) skeletons exhibit limited intraskeletal variation in carbon‐ and nitrogen‐isotope ratios, suggesting that sampling of distinct elements is appropriate for paleodiet studies. In contrast, individuals with osteomyelitis, healed fractures, and osteoarthritis exhibit significant intraskeletal differences in isotope values, depending on whether one is comparing lesions to near or to distant sites. Skeletons with periostitis result in significant intraskeletal differences in nitrogen isotope values only, while those with rickets/osteomalacia do not exhibit significant intraskeletal differences. Based on these results, we suggest that paleodiet researchers avoid sampling collagen at or close to lesion sites because the isotope values may be reflecting both altered metabolic processes and differences in diet relative to others in the population. Am J Phys Anthropol 153:598–604, 2014. © 2013 Wiley Periodicals, Inc.     

Stable isotopic evidence for diet at the Imperial Roman coastal site of Velia (1st and 2nd Centuries AD) in Southern Italy

Here we report on a stable isotope palaeodietary study of a Imperial Roman population interred near the port of Velia in Southern Italy during the 1st and 2nd centuries AD. Carbon and nitrogen stable isotope analyses were performed on collagen extracted from 117 adult humans as well as a range of fauna to reconstruct individual dietary histories. For the majority of individuals, we found that stable isotope data were consistent with a diet high in cereals, with relatively modest contributions of meat and only minor contributions of marine fish. However, substantial isotopic variation was found within the population, indicating that diets were not uniform. We suggest that a number of individuals, mainly but not exclusively males, had greater access to marine resources, especially high trophic level fish. However, the observed dietary variation did not correlate with burial type, number of grave goods, nor age at death. Also, individuals buried at the necropolis at Velia ate much less fish overall compared with the contemporaneous population from the necropolis of Portus at Isola Sacra, located on the coast close to Rome. Marine and riverine transport and commerce dominated the economy of Portus, and its people were in a position to supplement their own stocks of fish with imported goods in transit to Rome, whereas at Velia marine exploitation existed side‐by‐side with land‐based economic activities. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Stable isotope evidence for sex- and status-based variations in diet and life history at medieval Trino Vercellese, Italy

The medieval period in Europe was a time of unprecedented social complexity that affected human diet. The diets of certain subgroups-for example, children, women, and the poor-are chronically underrepresented in historical sources from the medieval period. To better understand diet and the distribution of foods during the medieval period, we investigated stable carbon and nitrogen isotope ratios of 30 individuals from Trino Vercellese, Northern Italy (8th-13th c.). Specifically, we examined diet differences between subgroups (males and females, and high- and low-status individuals), and diet change throughout the life course among these groups by comparing dentine and bone collagen. Our results show a diet based on terrestrial resources with input from C(4) plants, which could include proso and/or foxtail millet. Diets of low-status males differ from those of females (both status groups) and of high-status males. These differences develop in adulthood. Childhood diets are similar among the subgroups, but sex- and status-based differences appear in adulthood. We discuss the possibility of cultural buffering and dietary selectivity of females and high-status individuals.     

A stable isotope (δ13C and δ15N) perspective on human diet on rapa nui (Easter Island) ca. AD 1400–1900

Ecological and environmental evidence suggests that Rapa Nui was among the most marginally habitable islands in Eastern Polynesia, with only a fraction of the biotic diversity found on archipelagos to the west, and capable of sustaining many fewer cultigens traditionally transported by Polynesian colonizers. However, archaeological evidence for human dietary adaptations under such restrictions is limited. Little is known about the particulars of the subsistence base and dietary changes on Rapa Nui that may be associated with a hypothesized late prehistoric decline in the quality and diversity of food sources. To better understand prehistoric Rapa Nui diet we examined stable carbon and nitrogen isotope compositions of human teeth along with archaeological faunal material thought to comprise the Rapa Nui food web. Our results indicate that contrary to previous zooarchaeological studies diet was predominantly terrestrial throughout the entire sequence of occupation, with reliance on rats, chickens and C3 plants. While a few individuals may have had access to higher trophic level marine resources, this is evident only later in time (generally post–AD 1600). A decline in δ¹⁵N through time was observed, and may be attributed to declines in available terrestrial proteins; however, presently we cannot rule out the effect of changing soil and plant baseline δ¹⁵N. Our results also suggest differential access to higher trophic level marine resources among contemporaneous populations, but more research is required to clarify this observation. Am J Phys Anthropol 152:173–185, 2013. © 2013 Wiley Periodicals, Inc.     

Stable isotope evidence for 1500 years of human diet at the city of York, UK

We present here the results of a large-scale diachronic palaeodietary (carbon and nitrogen isotopic measurements of bone collagen) study of humans and animals from a single site, the city of York (U.K.), dating from the Roman period to the early 19th century. The human sample comprises 313 burials from the cemeteries of Trentholme Drive and Blossom Street (Roman), Belle Vue House (Anglo-Saxon), Fishergate (High and Later Medieval), and All Saints, Pavement (Later and Post-Medieval). In addition, 145 samples of mammal, fish and bird bone from the sites of Tanner Row and Fishergate were analyzed. The isotope data suggest dietary variation between all archaeological periods, although the most significant change was the introduction of significant quantities of marine foods in the Medieval periods. These are first evident in the diet of a small group of individuals from the High Medieval cemetery at Fishergate, although they were consumed almost universally in the following periods. The human isotope values are also remarkable due to unusually elevated delta(15)N ratios that are not sufficiently explained by the comparably small enrichment in (13)C that accompanies them. We discuss the possible reasons behind this and the archaeological significance of the data set.     

Dietary analysis of the herbivorous hemiramphid Hyporhamphus regularis ardelio: an isotopic approach

The stable isotope values for a range of size classes of Hyporhamphus regularis ardelio from Moreton Bay, south‐east Australia were determined. There was a positive linear relationship between δ¹³C and standard length (L_S)(δ¹³C = 0·034 L_S ? 16·23; r² = 0·78). δ¹³C ranged from ?8·48 to ?17·29‰ with the smallest size class (50 mm L_S) being on average 1·04‰ enriched with respect to that of zooplankton (Temora turbinata) and 7·97‰ depleted compared to Zostera capricorni. δ¹³C was positively correlated with L_S(P < 0·01)(more enriched with increasing L_S) with those fish of the largest size class (225 mm L_S) being 9·86 and 0·84‰ enriched than T. turbinata and Z. capricorni, respectively. There was no detectable trend in δ¹⁵N values with L_S(P > 0·01) with δ¹⁵N, ranging from 9·18 to 11·00‰. Fish of all size classes were on average 2·32 and 7·63‰ more enriched than zooplankton and seagrass, respectively. Carbon isotope data indicate that H. r. ardelio commence life as carnivores and change to a diet in which seagrass is the primary carbon source. The dependence on animal matter, however, is always present. Due to the low percentage of nitrogen in Z. capricorni(2·5%) compared to zooplankton (9·1%) it appears that nitrogen from zooplankton is necessary throughout their life history with the carbon requirements for these fish coming chiefly from Z. capricorni.     

Functional differentiation of African grazing ruminants: an example of specialized adaptations to very small changes in diet

We assess whether interspecific differences in craniodental morphology within a single ruminant feeding guild, the grazers, represent anatomical adaptations to subtle differences in diet. Differences in craniodental anatomy follow a distinct taxonomic pattern that is paralleled by dietary niche differentiation recorded in species' stable carbon (δ¹³C) and nitrogen isotope (δ¹⁵N) compositions, strongly supporting a hypothesis for functional divergence within the grazers. We propose that the evolutionary origin of grazers were multifold; at least two and up to four different types of grazing can be discerned within the 11 taxa studied here alone. However, correspondence between craniodental adaptations and isotopic differences across species are not found when only δ¹³C data are considered (i.e. morphological differences do not reflect varying proportions of C₃ browse to C₄ grass consumed). This implies that alternate anatomical adaptations to grazing are not related to differences between variable (part-time browsing) and obligate grazers, as previously predicted. Rather, anatomical differences correlate strongly with changes in δ¹⁵N, which we infer to reflect functional responses to changes in diet quality associated with the degree of feeding selectivity and short-, medium-, or tall-grass grazing.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 755–764.     

Iron Age breastfeeding practices in Britain: isotopic evidence from Wetwang Slack, East Yorkshire

We present here the results of carbon and nitrogen isotopic analysis of bone collagen undertaken on all skeletal remains of infants and young children below the age of 6 years (n = 34) from the internationally important British cemetery site at Wetwang Slack in East Yorkshire (middle Iron Age, ca. 4th to 2nd centuries BC). The aim of the study is to investigate infant diet, with particular reference to breastfeeding and weaning practices, and to compare the data with previously published studies of archaeological populations, particularly in the context of the variation in data patterns to be seen between sites. The skeletal remains from Wetwang Slack form the only prehistoric collection in the UK, prior to the Romano-British period, with sufficient individuals in this age group to make such an isotopic study viable alongside associated adults and older children. The data are compared in detail with published data from two other sites, one from 19th century Canada and the other from Medieval Britain. The results suggest an unusual situation at Wetwang Slack, with neither the nitrogen nor the carbon isotope ratios conforming to expectations when compared with the putative mothers. We discuss how these data compare with the expectation for breastfed infants and we interpret the divergence in this case to be due to restricted breastfeeding and the early introduction of supplementary foods.