The Characterization of Biologically Available Strontium Isotope Ratios for the Study of Prehistoric Migration

Strontium isotope analysis of bone and tooth enamel from prehistoric human skeletons is an important new technique used to address questions regarding migration. Two problems arise in such investigations: (1) levels of strontium isotope ratios in local bedrock, soil, water, plants and animals are variable; and (2) a range of values in human bone and enamel data make it difficult to distinguish some migrants from locals. Analysis of the bones of small animals provides a robust measure of local strontium isotope ratios and a reliable, if conservative, means for determining confidence limits for distinguishing migrants. Data from various geographical areas are presented here in a discussion of variability in strontium isotope values. Examples are provided using modern and prehistoric materials. We conclude with the recommendation that studies involving strontium isotope analysis should incorporate small animal samples for comparative purposes whenever possible.     

Evaluation of bone strontium as a measure of seafood consumption

The recognition that bone strontium/calcium ratios reflect dietary levels of strontium and that seawater has a high strontium content led some archaeologists to infer that seafood consumption produces high Sr/Ca ratios in bone. Analyses of seawater and of marine organisms reveal, however, a marine trophic effect comparable to the trophic effect seen in terrestrial food chains. This marine trophic effect reduces the Sr/Ca levels in seafood such that marine dietary resources have Sr/Ca levels comparable to those of terrestrial resources. Thus, bone Sr/Ca ratios can not differentiate consumption of marine and terrestrial resources. Also, Sr/Ca of bones from archaeological sites where seafood was an important component of diet were found to be within the range of entirely terrestrial diets. Copyright © 1999 John Wiley & Sons, Ltd.     

Strontium and calcium distribution in plants: Effect on palaeodietary studies

In palaeodietary studies it is assumed that no discrimination occurs during uptake by plants of calcium and strontium from the soil. Here, a compilation of distribution ratios is presented from which it is apparent that differences in Sr/Ca ratios within and between plants do exist. These differences affect Sr intake by humans and animals and thus should be taken into consideration when interpreting prehistoric human bone Sr levels in a dietary sense, and when selecting a herbivorous baseline species. In agricultural societies, human Sr intake may be diversified by differences in Sr/Ca ratios in various grain species and varieties.     

Tending and drive hunting: A density-mediated attrition model can explain age profiles of white-tailed deer at Iroquoian village sites

In a 1993 paper, Noble and Crerar suggested, based on the age and sex distribution of white-tailed deer (Odocoileus virginianus) longbones from four Attawandaron Iroquoian sites around the western end of Lake Ontario, that the contact-period Attawandaron were managing local deer populations, in response to the aboriginal trade in hides. Having observed similar patterns of differential preservation of elements and epiphyseal fusion at nearby Iroquoian sites that are not ascribed to the Attawandaron, and which pre-date the hypothesised trading period, we argue that these patterns may instead relate to bone density and/or vulnerability to taphonomic effects of late-fusing epiphyses. We further support our argument through age profiles based on dental eruption and wear.     

Prehistoric dietary adaptations among hunter-fisher-gatherers from the Little Sea of Lake Baikal,Siberia, Russian Federation

Dietary adaptations of prehistoric hunter-gatherers from Neolithic and Early Bronze Age cemeteries in the Little Sea region of Cis-Baikal (the region to the west and north of Lake Baikal) are explored using stable isotopes of carbon and nitrogen. Stable isotope data, including stable carbon isotopes from bone carbonate, are presented for 22 individuals from the site of Kurma XI, dated to approximately 6500 B.P. to 4000 B.P. Data are compared to previously analyzed individuals from the larger Early Bronze Age cemetery, Khuzhir-Nuge XIV (Katzenberg et al., 2009 JAS) and to smaller sites located along the shore of the Little Sea, including sites on Olkhon Island. An extensive collection of fauna, both prehistoric and modern, from the Little Sea and neighboring regions is also analyzed for stable isotopes of carbon and nitrogen. Clear distinctions are found in modern fish recovered from the Little Sea, in contrast to those from the open waters of the lake and from the neighboring Angara and Lena rivers. Considerable variation is seen in stable carbon isotope ratios from fish while stable nitrogen isotope ratios are not as variable, regardless of habitat. Isotope source modeling is used to assist in reconstructing past dietary adaptations. While there is ample evidence from other studies for cultural change over this temporal span, diet appears to have been relatively stable.     

Variation in strontium isotope ratios of archaeological fauna in the Midwestern United States: a preliminary study

Strontium isotope values (⁸⁷Sr/⁸⁶Sr) in bone and tooth enamel have been used increasingly to identify non-local individuals within prehistoric human populations worldwide. Archaeological research in the Midwestern United States has increasingly highlighted the role of population movement in affecting interregional cultural change. However, the comparatively low level of geologic variation in the Midwestern United States might suggest a corresponding low level of strontium variation, and calls into question the sensitivity of strontium isotopes to identify non-local individuals in this region. Using strontium isotopes of archaeological fauna, we explore the degree of variability in strontium ratios across this region. Our results demonstrate measurable variation in strontium ratios and indicate the potential of strontium analysis for addressing questions of origin and population movement in the Midwestern United States.     

Residential mobility and resource use in the Chiribaya polity of southern Peru: strontium isotope analysis of archaeological tooth enamel and bone

The Chiribaya were a complex polity during the Andean Late Intermediate Period (c. AD 1000–1300) in the Ilo and Moquegua Valleys of southern Peru. Recent research has demonstrated that the Chiribaya polity was a señorío, a confederacy of economically specialised parcialidades. Here we test hypotheses regarding the movement of individuals and resources among the Chiribaya‐affiliated sites of Chiribaya Alta, Chiribaya Baja, San Gerónimo and El Yaral, as well as from outside of the Ilo and Moquegua Valleys. Although archaeological human enamel and bone strontium isotope ratios from Chiribaya Baja and San Gerónimo cluster closely, there is a wider variety of strontium isotope ratios observed at Chiribaya Alta and El Yaral. This indicates that individuals buried in cemeteries at these sites had access to a wider variety of resources, and probably moved between different geological zones throughout their lifetimes. Copyright © 2007 John Wiley & Sons, Ltd.     

Paleonutritional and paleodietary survey on prehistoric humans from Las Cañadas del Teide (Tenerife,Canary Islands) based on chemical and histological analysis of bone

The aim of the present study is to perform a paleodietary and paleonutritional survey on 17 individuals buried in accordance with the prehispanic ritual in the central plateau of the island Tenerife, called Las Cañadas del Teide. We recorded hydrogen, nitrogen and carbon isotope compositions of human bone collagen, bone barium and strontium, and histomorphometrically assessed trabecular bone mass (TBM). Bone trace elements and TBM were compared with reference data derived from a modern sample consisting of 13 individuals. In addition, δ¹⁵N and δ¹³C values were determined in several modern indigenous plants, bone collagen of prehistoric domestic animals (goat and pig), and prehistoric wild animals (a giant lizard, Gallotia goliath and a giant rat, Canaryomis bravoi), which represent food sources potentially consumed by the prehistoric population of the Island. The carbon stable isotope composition of bone collagen ranged between ?20.5 and ?18.6‰ (VPDB), indicating a diet based on C₃ plants. Nitrogen isotope values ranged from 8.2 to 12.4‰ (AIR), suggesting a general meat-enriched diet, most likely domestic goats, of higher level consumers. Hydrogen isotope values ranged from ?18 to +4‰, whereas log Ba/Sr was greater than ?0.40 in the vast majority of cases. TBM showed a tendency to osteoporosis in 30% of the individuals analyzed. C-14 dating showed that two burial sites, including 5 individuals, belonged to the post-conquest era (after the 15th century), despite a fully “prehispanic” burial ritual, which lends credenceto the oral tradition that some of the prehispanic population fled to the highlands at the time of the Spanish conquest, and lived there during decades or even centuries. These individuals showed lower δD, δ¹³C and δ¹⁵N, and higher log Ba/Sr values than those buried before the Spanish conquest, suggesting dietary differences between the two groups. Also, women showed a trend to a higher consumption of vegetables than men.     

Effect of mollusc eating on human bone strontium levels

Empirical aspects of the movement of strontium through the food chain suggest that the level of bone strontium can be used as an indicator of the percentage of meat in human diet. In general, skeletal remains from agricultural peoples are expected to have high bone strontium levels relative to hunter-gatherers from the same geographical region because plants contain relatively higher amounts of strontium when compared with animal products. The results of the study described in this paper, however, indicate that the inclusion of molluscs as a component of the diet may produce the opposite of the expected strontium values. Burials from an Archaic (c. 2500 BC) hunting-gathering population excavated from Lu^o25, an archaeological site in northern Alabama, USA, exhibit a mean bone strontium level ( atomic absorption; neutron activation) that is higher than the mean level from an agricultural Mississippian (c. AD 1400) population ( atomic absorption; neutron activation) that was buried at the same site. The samples were analysed by two techniques (atomic absorption spectrometry and neutron activation analysis) and the results compared favourably; therefore, the results can be accepted as valid rather than being due to technique error. We propose that the ingestion of molluscs, whose meat is known to contain large amounts of strontium, has produced this reversal from expected results.     

NUCLEAR MAGNETIC RESONANCE SPECTROSCOPIC AND ISOTOPIC ANALYSIS OF CARBONIZED RESIDUES FROM SUBARCTIC CANADIAN PREHISTORIC POTTERY

Late prehistoric pottery is found in abundance at archaeological sites around Southern Indian Lake. Black residues, found on the two dominant vessel forms, flat plates and round pots, are presumed to be the remains of prehistoric meals. ¹³C cross-polarization magic-angle-spinning nuclear magnetic resonance spectroscopy (CPMAS NMR) and¹³C and¹⁵ N isotopic ratios and C/N ratios are used to reconstruct prehistoric diet and to shed light on possible uses for the plates. Samples of foods were cooked in clay pots, on a wood fire, to simulate the conditions of burning that could have produced the residue. Decomposition of carbohydrates, protein, and fat during cooking is studied with ¹³C CPMAS NMR, and the effect of cooking on isotopic and C/N ratios documented. Predominantly fish and fat were cooked in the pots, whereas the residues from plates contain a greater proportion of fat and could have been used as frying pans or possibly as fat-burning lamps placed on the ashes of a wood fire.     

Strontium isotope analysis to reveal migration in relation to climate change and ritual tooth ablation of Jomon skeletal remains from western Japan

A gradual population increase accompanying climate cooling has been evinced as having occurred in western Japan during the Middle (ca. 5000–4000 years BP) to Late-Final Jomon period (ca. 4000–2300 years BP). We test the hypothesis that this population change paralleled increasing human migration. We also test the archaeological hypothesis that types of ritual tooth ablation can be used to distinguish between locals and immigrants during the Late-Final Jomon period. We measured strontium isotope ratios in human skeletal remains from the Middle Jomon Ota and the Late-Final Jomon Tsukumo sites located in the Sanyo region of western Japan. Tooth enamel and bone were analyzed, and modern plant samples were collected in the areas surrounding the two sites to make a map of environmental strontium isotope ratios. The biosphere strontium isotope ratios correlated well with the underlying geology, enabling us to put forth a hypothesis of immigrants’ origins. There were no migration pattern differences between the Middle and Late-Final Jomon groups, indicating that the gradual population increase was caused by an increase in the indigenous population. All the Tsukumo individuals are locals, and this finding indicates that types of tooth ablation did not distinguish between locals and immigrants. Alternative hypotheses for the presence of different tooth ablation types in the Jomon society should be explored.     

CARBON ISOTOPE RATIOS IN PALAEODIET: LACK OF AGE OR SEX EFFECT

Palaeodiet of humans can be determined using stable carbon isotope ratios of bone collagen. Differences in δ¹³C-values between individuals in a population may be due to real differences in diet, or alternatively, they could be due to age- or sex-dependent differences in the physiologically controlled fractionation of carbon isotopes between food and collagen. The dependence of this fractionation on age and sex was tested in a study of 50 individuals of differing ages from a prehistoric population of bison hunters. The total variation in δ¹³C for bone collagen was found to be ± 0.3‰, indicating that variations larger than this, observed in other populations, are due to real dietary differences between individuals.     

Mobility or migration: a case study from the Neolithic settlement of Nieder-Mörlen (Hessen,Germany)

A combination of stable carbon and nitrogen isotope analysis of collagen and radiogenic strontium isotope analysis of tooth enamel was used to investigate diet and mobility at the early Neolithic settlement of Nieder-Mörlen in Germany. The carbon and nitrogen ratios suggest a mixed terrestrial based diet that is consistent with data previously published for early Neolithic sites in Europe. The strontium isotope data indicate a high degree of human mobility with only one individual having an isotope ratio consistent with locally derived strontium. Unusually, a group of non-local juveniles with isotope ratios typical of upland regions is also present at the settlement but there are no adult burials with such values. Whilst transhumance is considered as an explanation, it would not explain why these non-local juveniles lived foreshortened lives and other possible mechanisms are therefore discussed.     

THE FUNDAMENTAL RELATIONSHIP BETWEEN ANCIENT DIET AND THE INORGANIC CONSTITUENTS OF BONE AS DERIVED FROM FEEDING EXPERIMENTS

The levels of ten elements (phosphorus, calcium, magnesium, strontium, barium, potassium, sodium, zinc, iron, and aluminium) have been measured in the femurs and humeri of laboratory rats grown on test diets as a model for palaeodietary studies of excavated human skeletons. High levels of dietary fibre correlate with lower Ca and higher Sr and Ba in the bone. High values of the dietary Sr/Ca ratio correlate with high Sr levels in the bone. High levels of dietary protein correlate with lower Sr and higher Zn. High values of the ratio Ba/Ca and lower levels of Fe correlate with higher levels of Ba. Because bone levels typically are controlled by several dietary components, variation of the levels of a given element in the diet does not necessarily translate into analogous variations in bone. Only K and Fe in bone correlate highly with their levels in diet. The failure of bone Sr, Ba, and Zn to correlate positively with dietary levels is fully explicable in terms of their interdependence on other dietary components, such as Ca, P, Fe, protein, and fibre.     

Calcium isotopes in archaeological bones and their relationship to dairy consumption

The calcium isotope ratios (δ^44/42Ca) of bones from humans and fauna from three archaeological sites, Taforalt, Abu Hureyra, and Danebury, are evaluated in order to assess whether calcium isotope ratios of bones can be used to detect dairy consumption by adult humans. At each site the fauna δ^44/42Ca is the same regardless of species, while the humans have lower δ^44/42Ca than the local animals by 0.24–0.41‰ (site means). However we cannot ascribe this difference to dairy consumption, given this human–faunal difference also occurs in Epipalaeolithic and Mesolithic adult humans, where dairy consumption is unlikely. Rather, this difference appears to be a result of differences in metabolic processes or other aspects of diet between humans and fauna. Minimal isotopic change in sequential acid leaches of bone powders and consideration of the high calcium concentration in bone suggest that bone calcium isotope ratios are not substantially affected by diagenetic change.     

“Random” hunting and the composition of faunal samples from archaeological excavations: A modern example from New Zealand

The ability of analyses of the age- and sex-composition of faunal samples from archaeological excavations to permit reliable inferences concerning prehistoric culling practices and, in particular, to distinguish between wild and domesticated animals is investigated by examining the demographic composition of 14 groups of red deer (Cervus elaphus) shot at random from a helicopter in the Southern Alps of New Zealand in early 1975. It is concluded that such “random” hunting can produce samples of bones that are apparently biased with respect to age and/or sex. The implications of these findings for prehistoric studies are discussed briefly with particular reference to the exploitation of red deer in Italy and Switzerland, and greater caution in excavating and analysing faunal samples is urged.     

The Movement and Exchange of Dogs in the Prehistoric Caribbean: An Isotopic Investigation

This study explores the feasibility of using strontium isotope (⁸⁷Sr/⁸⁶Sr) analyses of enamel from domestic dogs (Canis familiaris) to investigate networks of exchange in the prehistoric Circum‐Caribbean. Dog teeth were obtained from burial and domestic contexts from two prehistoric sites (Anse à la Gourde and Morel) on Grande‐Terre, Guadeloupe (Lesser Antilles). Strontium isotope results were compared with local biosphere ⁸⁷Sr/⁸⁶Sr data at the scale of the site, island and archipelago. The isotope results indicate both local and nonlocal origins with three dogs (30%) identified as nonlocal (one from Anse à la Gourde and two from Morel). The variance in ⁸⁷Sr/⁸⁶Sr ratios of the nonlocal dog teeth is consistent with diverse multiple origins external to the island of Grande‐Terre but consistent with origins from other islands of the Lesser Antilles. The diverse origins of the nonlocal dog samples indicate that the prehistoric circulation of dogs occurred at multiple scales from regional to long distance. Significantly, the ⁸⁷Sr/⁸⁶Sr ratios of some of the dog teeth are comparable with values of nonlocal humans at Anse à la Gourde determined in previous studies. It is possible that these comparable ⁸⁷Sr/⁸⁶Sr ratios result from similar natal origins, for example if individuals were migrating to Guadeloupe with dogs. The results of this study contribute to an ongoing regional investigation of the economic, social and political roles of animals and animal remains and the multiscalar networks of prehistoric mobility and exchange in the Circum‐Caribbean region. Copyright © 2013 John Wiley & Sons, Ltd.     

The Ethnoarchaeology of Reptile Remains at a Lake Turkana Occupation Site, Kenya

The role of reptiles in hominid hunter–gatherer subsistence in Pleistocene Africa has been largely overlooked. This study examines the reptile component of a modern lake shore camp (site 20) assemblage of low archaeological visibility. Site 20, located on the eastern shore of Lake Turkana, has been observed from its creation to burial. The site is an ideal modern analogue for the interpretation of African prehistoric archaeological sites. Patterns of element loss, and patterns of bone modifications, namely burn, cut and slice marks, are examined. From this baseline data, three conclusions are drawn regarding the interpretability of reptile remains found at archaeological lakeside sites: (1) the MNI of crocodile remains at a site is likely to be similar to the original number of individuals which contributed to the deposited assemblage; (2) the MNI estimates of the turtle component will be much less than the original number of individuals in the deposited assemblage; and (3) patterns of bone modifications can be related to hominid food procurement and processing activities.     

MIDDLE HOLOCENE PERIODICITIES IN RAINFALL INFERRED FROM OXYGEN AND CARBON ISOTOPIC FLUCTUATIONS IN PREHISTORIC TROPICAL ESTUARINE MOLLUSC SHELLS

Stable oxygen and carbon isotopic ratios in modern and archaeological estuarine mollusc shells, Polymesoda radiata, change in accordance with seasonal salinity fluctuations in the Acapetahua estuary located on the Pacific coast of southern Mexico. This region receives ?3000 mm of precipitation annually, most during a wet season between April and October. The changing flux of fresh water and organic detritus into the estuary causes large changes in the oxygen and carbon isotopic composition of the estuarine waters and in the carbonate precipitated by P. radiata. Oxygen isotopic ratios in the shells of molluscs collected by late Archaic period populations (5000–4000 BP) in this region indicate that patterns of rainfall were similar to today. Modern shells, however, exhibit much more negative carbon isotopic values than observed in prehistoric shells. This change may be associated with the input of modern fertilizers into the estuary.     

GEOGRAPHICAL PATTERNS IN BIOLOGICALLY AVAILABLE STRONTIUM,CARBON AND OXYGEN ISOTOPE SIGNATURES IN PREHISTORIC SW GERMANY*

In order to interpret strontium and oxygen isotope values in Neolithic human skeletons analysed previously, we begin to map the biologically available strontium, carbon and oxygen isotopic signatures of prehistoric southern Germany by analysing tooth enamel of pigs from archaeological sites distributed around the region. The mapping shows a marked upland–lowland difference in biologically available ⁸⁷ Sr/ ⁸⁶ Sr values, ranging between 0.7086 and 0.7103 in the sedimentary lowlands, and from 0.710 to as high as 0.722 in the crystalline uplands of the Odenwald, the Black Forest and the Bavarian Forest. In addition, carbon isotopes in the carbonate fraction of pig enamel were generally about 1–2 more enriched in ¹³ C in the uplands. Despite the expected depletion of ¹⁸ O with altitude, oxygen isotopes in pig enamel showed little correlation with site altitude, although for pig samples not older than the Iron Age there was some geographical correlation withδ¹⁸O patterns in modern precipitation.