Reconstructing dietary and environmental history from enamel isotopic analysis: time resolution of intra‐tooth sequential sampling

The carbon and oxygen isotopic composition of the mineral phase of tooth enamel is linked to diet and environment. Enamel is not remodelled once formed. Several studies of intra‐tooth isotopic variability in hypsodont mammal teeth have involved sequential sampling of enamel in order to detect changes in diet and environment during tooth formation. The possibility of exploring individual history opens the door to many applications, particularly in palaeoenvironment and herd management reconstruction. However, previous histological investigations have shown that enamel mineralization is a progressive and discontinuous process. The goal of the present study is to determine if this pattern significantly influences the time resolution of an intra‐tooth sequential sampling. Isotopic analyses (δ¹³C) were performed on tooth enamel from steers (Bos taurus) that had changed from a C₃ plant‐based diet to a C₄ plant‐based diet with very different carbon isotopic compositions. The change of diet was reflected in the mineral phase of enamel. The pattern of intra‐tooth isotopic variation suggests that completion of enamel mineralization required six to seven months. Such a lag in enamel mineralization will decrease the time resolution of enamel sequential sampling. The effects of prolonged mineralization of enamel have to be considered when interpreting patterns of intra‐tooth isotopic variations. Copyright © 2002 John Wiley & Sons, Ltd.     

A strontium isotope analysis on the relationship between ritual tooth ablation and migration among the Jomon people in Japan

Distinct patterns can be discerned in the extensive ritual tooth ablation found among the human skeletal remains of the Late–Final Jomon period (ca. 3200–2800 cal BP) in Japan. Based on comparative observations of sex and grave patterns in the skeletal remains, two major patterns in ritual tooth ablation, termed type 4I and type 2C, have been assigned to locals and immigrants, respectively. In order to test this hypothesis, strontium (Sr) isotope (⁸⁷Sr/⁸⁶Sr) analyses were performed on human skeletal remains from the Yoshigo shell mound in Aichi Prefecture, central Japan. Plants in the surrounding area were also examined to illustrate the geographic ⁸⁷Sr/⁸⁶Sr distribution. The Sr isotopic variation in human tooth enamel (⁸⁷Sr/⁸⁶Sr = 0.70868–0.71028) was greater than that in human bones (⁸⁷Sr/⁸⁶Sr = 0.70871–0.70943). Individuals with higher Sr isotope ratios in their tooth enamel than seawater Sr values of 0.7092 can be identified as immigrants (36% of population). The presence of these isotopically identified immigrants between both type 2C and type 4I individuals does not support the previous hypothesis. The intra-population ⁸⁷Sr/⁸⁶Sr distribution of tooth enamel of type 2C individuals showed a significantly higher mean ratio than that of type 4I individuals, suggesting a higher proportion of immigrants among the former.     

A longitudinal study of tooth growth in a single individual based on long- and short-period incremental markings in dentine and enamel

Ground sections of teeth from a single individual revealed approximately 30 fluorescent lines in the dentine resulting from successive courses of tetracycline antibiotics given over a period of approximately 12 years. In addition, many teeth showed long-period incremental markings in the dentine. Short-period daily cross-striations in the enamel were used to calculate the periodicity of the long-period incremental lines in both enamel and dentine. The incremental markings in the dentine were then used to calibrate the time of administration of each of the courses of tetracycline antibiotics. Enlarged micrographs of the teeth, constructed using fluorescence microscopy, were used to measure the increase in height of different teeth throughout the growth period on each occasion the tetracycline antibiotics were given. The times of initial mineralization of the teeth and the duration of crown formation were also determined for each tooth section. Line plots of tooth height against age were computed and used to calculate the rate of increase in tooth height during crown and root formation for one example of each tooth type. Initial rates of increase in height during enamel apposition and coronal dentine formation were fast, between 10 μm and 14 μm per day. During the latter phase of crown formation and during early root formation, tooth height increased at a slower rate of between 4 μm and 6 μm per day. Rates of increase in tooth height then rose to between 13 μm and 26 μm per day during the second half of root formation before falling off to a rate of approximately 4 μm per day during root completion (as the root apex formed). The times of initial crown mineralization and the total crown formation times estimated in this individual were all within the range known for modern humans but there was comparatively early mineralization of the third permanent molar. These findings are discussed in the context of other studies on human dental development.     

In situ oxygen isotope micro-analysis of faunal material and human teeth using a SHRIMP II: a new tool for palaeo-ecology and archaeology

A Sensitive High Resolution Ion MicroProbe (SHRIMP II) has been used to make high spatial resolution in situ micro-analyses of oxygen isotopes in fish otoliths, and teeth from fossil herbivores and a Neanderthal. Large intra-tooth variations in the oxygen isotopic composition (up to 9‰) were observed in the enamel of herbivores from the Neanderthal fossil site of Payre, consistent with preservation of seasonal cyclicity. The range of isotopic compositions observed in Neanderthal tooth enamel was much smaller (∼3‰), possibly the result of a longer enamel maturation time averaging out variability. An archaeological otolith from a Preceramic site in Northern Peru exhibited marked changes in δ¹⁸O over life, due either to the fish occasionally migrating from the sea to a lower salinity habitat, or to short-lived rises in sea water temperature. A fish otolith from Australia's Willandra Lakes World Heritage Area showed clear seasonal variations, but also a general trend towards isotopically heavier and more saline water, as indicated by higher δ¹⁸O and Sr/Ca values resulting from increased evaporation. The results of these case studies are compared to results of oxygen isotope analysis using more conventional methods and demonstrate the ability of the SHRIMP II to provide precise high spatial resolution in-situ oxygen isotope analyses of a variety of biogenic materials. This approach has major advantages over conventional methods. It can provide rapid, micro-scale isotopic analyses of sub-permil precision without the need for chemical preparation of the sample.     

Seasonality and season of birth of modern and late Neolithic sheep from south-eastern France using tooth enamel δO analysis

Stable oxygen isotopic analysis of tooth enamel was used to investigate seasonality and season of birth in sheep. Analyses were performed on the teeth of eight modern sheep bred at the Carmejane farm in south-eastern France and born in different periods of the year. This reference data set confirms that oxygen isotopic records in the second and third molars can be used to differentiate between sheep born in late winter and those born in early autumn. The results show that inter-individual variability in the timing of tooth formation is low for the second lower molar and more pronounced for the third lower molar in this population. The duration of the process of enamel mineralization has been estimated at approximately six months. The teeth of four sheep and two goats from the late Neolithic site of Collet-Redon in south-eastern France were analyzed using the same methodology. At this site, lambing occurred between the late winter and early spring. A slight difference appears in the seasonal sequence recorded in sheep and goat, although it cannot be determined, whether this is due to different timing of tooth development, or an actual shift in the birth period. From the distribution of slaughter ages and birth period, it is suggested that domestic caprines were killed throughout the year and that Collet-Redon was probably a permanent settlement.     

Strontium isotope evidence of migration and diet in relation to ritual tooth ablation: a case study from the Inariyama Jomon site,Japan

Ritual tooth ablation was extensively practiced among Jomon (Japanese Neolithic) societies in their final phase (ca. 3000-2300 BP). This tradition includes two different tooth ablation patterns, type 4I and type 2C, referring to extraction of the mandibular incisors and canines, respectively. However, the reason for this difference is unclear. Previous carbon and nitrogen stable isotope analysis of human remains from the Inariyama shell mound revealed that type 4I individuals were more dependent on terrestrial resources and type 2C individuals on marine resources. To test this hypothesis, we performed strontium (Sr) isotope (⁸⁷Sr/⁸⁶Sr) analyses on the same skeletal remains and on modern plants around the site. Because Sr isotope ratios of plants differ according to the local geology and seawater has a consistent Sr isotope ratio, the Sr isotope ratios of tooth enamel can reveal both migration and diet. Comparing Sr isotope ratios in plants and seawater with those of tooth enamel, we identified four possible immigrants. Type 4I locals had significantly higher Sr isotope ratios than type 2C locals. The ratios of the type 4I and type 2C locals were close to those of terrestrial plants and seawater, respectively, suggesting that type 4I locals had incorporated much Sr from terrestrial resources and type 2C locals from marine resources. These results support the hypothesis that ritual tooth ablation reflects dietary differences throughout an individual’s life, and they suggest possible occupational differentiation among the Jomon people.     

INVESTIGATING SEASONALITY AND SEASON OF BIRTH IN PAST HERDS: A REFERENCE SET OF SHEEP ENAMEL STABLE OXYGEN ISOTOPE RATIOS

Intra‐tooth sequential analysis of enamel δ¹⁸O is currently used to investigate birth seasonality in past animal populations, offering new insights into seasonal availability of animal resources, herd management and seasonality of site occupation. Reference data sets are still required to address two major difficulties: (1) that inter‐individual variability in the record of the seasonal cycle is affected by tooth size; and (2) that the season of birth cannot be directly estimated from the timing of tooth growth, because of a delay in enamel mineralization. We present a data set acquired on the lower second molar of 10 modern sheep from Rousay (Orkney) born within a few weeks of each other in April/May and submitted to the same environmental conditions until death. All sheep have recorded a sinusoidal pattern of δ¹⁸O variation spanning approximately a year. From the difference between the expected and the measured time sequence, the delay of enamel mineralization is estimated to be 5–6 months. The data set is then described using a model mainly based on a cosine function. The period, corresponding to the length of the M2 crown formed over a year, averaged 35.8 mm. A very slight variation of tooth growth rate with time and no attenuation of the isotopic signal towards the cervical margin of the crown could be detected in this data set. The lowest δ¹⁸O values, corresponding to the sheep's first winter, were tracked at a distance from the enamel/root junction that varied between 23.0 and 30.3 mm (x_min mean = 27.6 mm); the highest δ¹⁸O values, corresponding to the sheep's second summer, were between 6.3 and 11.6 mm (x_max mean = 9.9 mm). Most of the variability can be attributed to tooth size. When normalized on the period, x_min and x_max are 0.28 (± 0.05) and 0.78 (± 0.05) on average, meaning that the Rousay sheep have recorded the minimum and maximum δ¹⁸O values on average at 78% and 28%, respectively, of the end of the periodic cycle recorded in the second molar.     

Mobility and the diversity of Early Neolithic lives: Isotopic evidence from skeletons

Isotopic analyses of tooth enamel from early Neolithic skeletons in southern Germany adds diversity to the picture of the Neolithic transition in central Europe, which has often been described as a wholesale shift in diet and technology. Over the past decade, these isotopic studies have suggested some degree of immigration from nearby indigenous groups, as well as social differences within early Neolithic communities that correlate with immigration patterns. In general, there emerges pattern a pattern of patrilocal kinship that is consistent with independent genetic evidence, and anthropologically consistent with the potential identification of Neolithic ‘nuclear families’; and finally, specialisation of subsistence activities, such as livestock herding and cultivating, probably along hereditary lines.     

EXAMINING CHILDHOOD DIETS AT KAMINALJUYU,GUATEMALA, THROUGH STABLE ISOTOPIC ANALYSIS OF SEQUENTIAL ENAMEL MICROSAMPLES*

Stable carbon and oxygen isotope ratios of tooth enamel provide a means to examine nutritional changes during childhood. To date, such studies have used large enamel samples, often spanning the developmental period of the tooth. This paper reports the results of small samples drilled from first molars and premolars of human teeth from Kaminaljuyu, a Classic period city in highland Guatemala. Carbon isotopes show considerable increase between cuspal and cervical enamel for both teeth, indicating an increase in maize consumption during childhood. Oxygen isotope trends are more variable, and suggest some seasonal fluctuation. While the oxygen isotope data confirm the identification of foreign skeletons among the samples, they illustrate a need for caution when sampling teeth due to variable δ¹⁸O composition of enamel within a tooth.     

New Statistical Approaches to Intra‐individual Isotopic Analysis and Modelling of Birth Seasonality in Studies of Herd Animals

This paper introduces improved methods for statistically assessing birth seasonality and intra‐annual variation in δ¹⁸O from faunal tooth enamel. The first method estimates input parameters for use with a previously developed parametric approach by C. Tornero et al. The second method uses a non‐parametric clustering procedure to group individuals with similar time‐series data and estimate birth seasonality. This method was successful in analysing data from a modern sample with known season of birth, as well as two heterogeneous archaeological data sets. Modelling indicates that the non‐parametric approach estimates birth seasonality more successfully than the parametric method when less of the tooth row is preserved. The new approach offers a high level of statistical rigour and flexibility in dealing with the time‐series data produced through intra‐individual sampling in isotopic analysis.     

Lead isotope ratios: Tracking the migration of European‐Americans to Grafton,Illinois in the 19th century

Lead isotope analysis was conducted using inductively coupled plasma mass spectrometer (ICP‐MS) instruments on local soil samples and human premolar tooth enamel from a 19th century population from Grafton, Illinois, USA. The goal of the study was to determine if lead isotope analysis could be used to infer place of birth and patterns of 19th century migration into the city of Grafton. Five soil core samples from a location near Grafton, Illinois, five grave soil samples from the city cemetery and the tooth enamel of 19 human premolars were analysed. The results of the soil core analysis indicated that the lead isotopic signature of Grafton differs significantly from isotope ratios of other geographic areas associated with recorded places of birth of 19th century Jersey County residents. Elemental and isotope analysis of the soil samples indicated that diagenesis was not a factor in the analysis of lead isotopic signatures of enamel. From the lead isotope analysis of human premolars, the geographic origin of 13 of the remaining 15 individuals could be inferred. The inferred geographic origin was supplemented by an analysis of 1860 mortality and census records and demonstrated the utility of using lead isotope analysis in bio‐archaeological investigations. Copyright © 2010 John Wiley & Sons, Ltd.     

The ‘Headless Romans’: multi-isotope investigations of an unusual burial ground from Roman Britain

Recent excavations at Driffield Terrace in York (Northern England) revealed an extremely unusual Romano-British cemetery of probably all-male composition, more than half of the individuals decapitated and with high incidence of other peri- and antemortem trauma. This paper presents the results of multi- (carbon, nitrogen, oxygen and strontium) isotopic analyses of bone and dentine collagen (n = 68) and tooth enamel (n = 18) which were conducted to obtain further information on the identity of these individuals and, more generally, in order to investigate the relationship between burial rite and geographical origin in a Roman provincial capital. The results show that the childhood origins of the “Headless Romans” were significantly more diverse than those of humans from other cemeteries in Roman York, but they demonstrate also that similar, unusual burial rites do not necessarily indicate a common geographical origin. Of particular interest were two individuals whose diet contained a significant proportion of C₄ plant (probably millet)-based protein. These are the first such isotope values observed in Britain from any archaeological time-period. Millet was not cultivated in the British Isles in antiquity and the results therefore demonstrate the value of palaeodietary data for assisting in isotopic mobility studies.     

The children of Kaminaljuyu: Isotopic insight into diet and long distance interaction in Mesoamerica

Known for its spectacular tombs and adobe talud–tablero architecture, the highland Guatemalan city of Kaminaljuyu is key to models of long distance interaction in Mesoamerica. We use stable isotopic data from human bone, dentine and tooth enamel to reconstruct Kaminaljuyu’s dietary history. Stable carbon isotope ratios and alkaline earth ratios of enamel carbonate indicate a decline in maize consumption from Preclassic to Classic periods, perhaps due to the desiccation of Lake Miraflores, which was used to irrigate Late Preclassic fields. Stable oxygen and strontium isotope ratios in enamel shed light on the geographic origin of Early Classic skeletons, and show that the central skeletons in the tombs were local children. However, four decapitated skulls and two peripheral skeletons show enriched oxygen ratios, similar to Lowland Maya sites. Strontium isotope ratios indicate that most of these are from an area underlain by Cretaceous limestones; one is from a metamorphic region. Two individuals may have traveled to or from Central Mexico. The greater evidence for lowland individuals among the tomb skeletons implies that political connections with the Maya area were more significant to elites at Kaminaljuyu than was direct contact with Central Mexico.     

Refining oxygen isotope analysis in the Nasca region of Peru: An investigation of water sources and archaeological samples

The development of complex societies, irrigation agriculture and sociopolitical transitions are of interest to researchers working in the Nasca region on the south coast of Peru. Occupied for thousands of years, many questions regarding the circumstances of these changes in the area are being investigated. Oxygen isotope analysis provides a method for exploring residential mobility of past peoples during these transitions. This study presents new δ¹⁸O data from water sources that would have been used by the ancient inhabitants, providing important information regarding the oxygen isotope variability in the region and the necessary baseline data for migration studies in this region. Our results suggest that the isotopic composition of water sources in the Nasca region is not highly variable. In addition, archaeological human tooth enamel samples from the sites of La Tiza and Pajonal Alto are analysed. The δ¹⁸O_c results of the human enamel samples confirm the local nature of the burial population, as suggested by previous strontium isotope analysis (⁸⁷Sr/⁸⁶Sr). Copyright © 2010 John Wiley & Sons, Ltd. This article was published online on 13 January 2010. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected 15 January 2010.     

Interpreting Oral Pathology at Machu Picchu,Peru

This study analyzes oral pathological conditions—caries, antemortem tooth loss, and occlusal macrowear—among adults (N = 70) interred at Machu Picchu, Peru. Previous isotopic diet reconstructions at Machu Picchu suggest substantial early‐life variation that may have narrowed somewhat by the last decade of life. This study seeks to further elucidate the intersection of diet, sex, and health at Machu Picchu by analyzing oral pathological conditions with existing carbon and nitrogen isotopic data. Observed caries prevalence is corrected to control for age and tooth loss, and is described for both anterior and posterior teeth; wear data are scored and reported for individual tooth types. Results indicate caries prevalence consistent with carbohydrate‐rich diets and no significant difference between males and females. However, no significant isotopic parameters are associated with caries prevalence in young adult males, while caries prevalence is significantly associated only with enamel carbonate δ¹³C in older adult males. Dietary protein sources, but not C₄ resources, are associated with caries prevalence in young adult females, and to a lesser degree in older adult females. Significant associations between occlusal wear and caries exist among young adult males and young adult females, but involving different tooth types. These findings suggest differential protein consumption at Machu Picchu between males and females, and separate masticatory and physiological processes shaping caries prevalence between the sexes at the site. This study therefore underscores the role that gender roles may have played in diet variation among this population and the need to account for sex in analyzing oral pathology. Copyright © 2013 John Wiley & Sons, Ltd.     

Subsistence and mobility strategies in the Epipalaeolithic: a stable isotope analysis of human and faunal remains at 'Uyun al-Hammam,northern Jordan

This paper investigates evidence for subsistence and settlement activities in the Levantine Middle Epipalaeolithic through the application of stable isotope analysis to human and non-human remains from the site of 'Uyun al-Hammam, northern Jordan. In general, bone from the site suffers a high degree of diagenesis and collagen could not be extracted for analysis here. Carbon and oxygen isotopic values from human tooth enamel samples were variable, but within expected values for the Middle Epipalaeolithic, whereas animal carbon and oxygen isotopic values varied widely, most likely due to hydrological and climatological factors. Carbon and isotopic values for the human samples indicated a predominantly C₃ plant dietary input, while animal samples appeared to have varying amounts of C₄ inputs into their diet. This is the first isotopic analysis conducted on material from the Middle Epipalaeolithic of the southern Levant and, as such, even results constrained by temporal and climatological variants within the region contribute to the overall knowledge of settlement and subsistence strategies during this cultural period.     

Lead isotope analysis of intra‐skeletal variation in a 19th century mental asylum cemetery: diagenesis versus migration

Living bone sequesters environmental lead (Pb) from both inhalation and ingestion, providing a record of Pb exposure over a lifetime. Questions about the effects of diagenesis and how to remove them have hampered most isotopic and elemental determinations. As a result, researchers often restrict their analyses to tooth enamel, despite its limitations. We report Pb isotopes in teeth and bones in a frontier population of 15 individuals from a late 19th century mental hospital graveyard in Pueblo, Colorado, a town active at that time in the smelting of ores. Analysis of lead isotopes sequestered in healing bone from rib fractures gives an isotopic fingerprint from the last few months of individual's lives. When bone tissues or teeth from different stages of life are analysed, life history trajectories such as migration routes can be developed which are partially self‐correcting for diagenesis. Copyright © 2005 John Wiley & Sons, Ltd.     

Laser ablation depth profiling of U-series and Sr isotopes in human fossils

We have explored laser depth profiling to obtain data sets for U-series as well as Sr analyses. Laser probing with an 81 μm spot size allows for the exploration of low uranium domains of up to 400 μm below the outer surface in tooth enamel. These low U domains will contain Sr isotope compositions of the individual, that are least affected by diagenetic Sr overprints. The small holes drilled for U surveying are not visible to the naked eye. Using larger spot sizes of around 233 μm, laser drilling can be used to obtain reliable U-series isotope data to a depth of approximately 1000 μm in enamel and around 1300 μm in bone. Furthermore, meaningful ⁸⁷Sr/⁸⁶Sr isotope data can also be obtained with this spot size. Using our sampling strategy, the overall damage to a human tooth is minute, as demonstrated on a Neanderthal tooth from Moula-Guercy. We expect that laser ablation depth profiling will become routine for gaining insights into the age of human fossils and the migrations of ancient humans.     

Dietary changes and millet consumption in northern France at the end of Prehistory: Evidence from archaeobotanical and stable isotope data

Diachronic changes of dietary human habits between the Neolithic and the Bronze Age are mainly identified through archaeological artefacts and archaeozoological and archaeobotanical studies. This paper aims to demonstrate the importance of a multi-disciplinary approach for palaeodietary studies and to identify the food changes between Neolithic and Bronze Age human groups in northern France. These changes are probably linked to the introduction of new crops, such as millet, and the use of stable isotope analysis on bones and teeth proves to be an effective method for assessing the role of this specific cereal in the diet and the economy. Stable isotope analyses were performed on bone and tooth collagen and apatite from eight humans and five domestic animals from a Late Bronze Age site (LBA; Barbuise; 15th–13th c. BC; Aube). The studied corpus is compared with isotopic data from human and animal bones from a nearby Neolithic site (Gurgy; 5th mill. BC; Yonne) and regional Neolithic to Iron sites located in northern France. Moreover, Barbuise data are supplemented by information from an important archaeobotanical study carried out on 21 LBA and Early Iron Age sites in the region. Neolithic and LBA human collagen isotopic ratios (δ¹³C, δ¹⁵N) differ statistically, as do those of some animals. Carbon isotopic ratios of human apatite corroborate collagen results indicating the consumption of ¹³C enriched food by LBA humans and animals compared to Neolithic samples. The high number of occurrences of plant remains in the Bronze Age settlements near the site points to the consumption of C₄ plants, such as millet, and would account for these results.     

Do silica phytoliths really wear mammalian teeth?

There is considerable literature suggesting that silica (opal) phytoliths cause dental enamel microwear in mammals. Much of this literature cites a single study from 1959 as evidence that silica phytoliths are harder than mammalian tooth enamel and so have the potential to cause dental microwear. No other studies using similar methodology have actually confirmed whether phytoliths are harder than dental enamel.