Reconstruction of breastfeeding and weaning practices using stable isotope and trace element analyses: A review

Bone spoons for prehistoric babies: Detection of human teeth marks on the Neolithic artefacts from the site Grad-Starčevo (Serbia)

Around 8000 years ago, throughout the Neolithic world a new type of artefact appeared, small spoons masterly made from cattle bone, usually interpreted as tools, due to their intensive traces of use. Contrary to those interpretations, the small dimensions of spoons and presence of intensive traces of use led us to the assumption that they were used for feeding babies. In order to test that assumption we compared 2230 marks on three spoons from the Neolithic site of Grad-Starčevo in Serbia (5800-5450 cal BC) with 3151 primary teeth marks produced experimentally. This study has shown that some of the marks on spoons were made by primary teeth, which indicate their usage in feeding babies. The production of a new type of artefact to feed babies is probably related to the appearance of a new type of weaning food, and the abundance of spoons indicates that new baby gruels became an important innovation in prehistoric baby-care.

Reconstructing breastfeeding and weaning practices in the Bronze Age Near East using stable nitrogen isotopes

Objectives

Breastfeeding and childhood diet have significant impact on morbidity and mortality within a population, and in the ancient Near East, it is possible to compare bioarchaeological reconstruction of breastfeeding and weaning practices with the scant textual evidence.

Materials and Methods

Nitrogen stable isotopes (δ¹⁵N) are analyzed here for dietary reconstruction in skeletal collections from five Bronze Age (ca. 2,800–1,200 BCE) sites in modern Lebanon and Syria. We employed Bayesian computational modeling on cross‐sectional stable isotope data of collagen samples (n = 176) mainly from previous studies to test whether the bioarchaeological evidence aligns with the textual evidence of breastfeeding and weaning practices in the region, as well as compare the estimated weaning times to the global findings using the WARN (weaning age reconstruction with nitrogen isotope analysis) Bayesian model.

Results

Though the Near East sites in this study had different ecological settings and economic strategies, we found that weaning was introduced to the five sites at 0.5 ± 0.2 years of age and complete weaning occurred around 2.6 ± 0.3 years of age on using the WARN computational model. These weaning processes are within the time suggested by historical texts, though average estimated weaning age on the Mediterranean coast is later than inland sites.

Discussion

Compared globally, these Near Eastern populations initiated the weaning process earlier but completed weaning within the global average. Early initial weaning may have created short spacing between pregnancies and a high impact on demographic growth within these agricultural populations, with some variation in subsistence practices accounting for the inland/coastal discrepancies.

Palaeoproteomic identification of breast milk protein residues from the archaeological skeletal remains of a neonatal dog

Accurate postmortem estimation of breastfeeding status for archaeological or forensic neonatal remains is difficult. Confident identification of milk-specific proteins associated with these remains would provide direct evidence of breast milk consumption. We used liquid chromatography coupled to tandem mass spectrometry (MS) to confidently identify beta-lactoglobulin-1 (LGB1) and whey acidic protein (WAP), major whey proteins associated with a neonatal dog (Canis lupus familiaris) skeleton (430–960 cal AD), from an archaeological site in Hokkaido, Japan. The age at death of the individual was estimated to be approximately two weeks after birth. Protein residues extracted from rib and vertebra fragments were analyzed and identified by matching tandem MS spectra against the dog reference proteome. A total of 200 dog protein groups were detected and at least one peptide from canine LGB1 and two peptides from canine WAP were confidently identified. These milk proteins most probably originated from the mother’s breast milk, ingested by the neonate just before it died. We suggest the milk diffused outside the digestive apparatus during decomposition, and, by being absorbed into the bones, it partially preserved. The result of this study suggests that proteomic analysis can be used for postmortem reconstruction of the breastfeeding status at the time of death of neonatal mammalian, by analyzing their skeletal archaeological remains. This method is also applicable to forensic and wildlife studies.

A probable case of infantile cortical hyperostosis in 2nd-4th centuries AD Romania

OBJECTIVE

This study aims to discuss the differential diagnosis for the pathological alterations displayed on an infant skeleton from Romania.

MATERIALS

One infant skeleton retrieved form the bathhouse of an abandoned Roman fort and dated between the 2nd and the 4th centuries AD.

METHODS

All available skeletal elements were analyzed macroscopically. In addition, the isotopic signatures (δ13C and δ15N) and the control region of the human mitochondrial genome for this archaeological sample were analyzed.

RESULTS

Based on dental development and long bone length, the skeleton was aged between birth and 2 months of age. Pathological lesions were noted on the mandible and diaphyses of long bones, but spared the metaphyses.

CONCLUSIONS

The perinatal age of the individual, along with lesion morphology and location, suggests a diagnosis of infantile cortical hyperostosis.

LIMITATIONS

The analysis would benefit from further stable isotope and mitochondrial genome analyses, which was limited due to the absence of comparative human and faunal remains from the site.

SUGGESTIONS FOR FURTHER RESEARCH

Further multidisciplinary research on human archaeological remains from Romania would provide a clearer image of past disease and life histories in this geographic area.

Multidisciplinary investigations of the diets of two post-medieval populations from London using stable isotopes and microdebris analysis

This paper presents the first multi-tissue study of diet in post-medieval London using both the stable light isotope analysis of carbon and nitrogen and analysis of microdebris in dental calculus. Dietary intake was explored over short and long timescales. Bulk bone collagen was analysed from humans from the Queen's Chapel of the Savoy (QCS) (n = 66) and the St Barnabas/St Mary Abbots (SB) (n = 25). Incremental dentine analysis was performed on the second molar of individual QCS1123 to explore childhood dietary intake. Bulk hair samples (n = 4) were sampled from adults from QCS, and dental calculus was analysed from four other individuals using microscopy. In addition, bone collagen from a total of 46 animals from QCS (n = 11) and the additional site of Prescot Street (n = 35) was analysed, providing the first animal dietary baseline for post-medieval London. Overall, isotopic results suggest a largely C₃-based terrestrial diet for both populations, with the exception of QCS1123 who exhibited values consistent with the consumption of C₄ food sources throughout childhood and adulthood. The differences exhibited in δ¹⁵N_coll across both populations likely reflect variations in diet due to social class and occupation, with individuals from SB likely representing wealthier individuals consuming larger quantities of animal and marine fish protein. Microdebris analysis results were limited but indicate the consumption of domestic cereals. This paper demonstrates the utility of a multidisciplinary approach to investigate diet across long and short timescales to further our understanding of variations in social status and mobility.

Cost-effective density functional theory (DFT) calculations of equilibrium isotopic fractionation in large organic molecules

The application of stable isotopes to address a wide range of biochemical, microbiological and environmental problems is hindered by the experimental difficulty and the computational cost of determining equilibrium isotopic fractionations (EIF) of large organic molecules. Here, we evaluate the factors that impact the accuracy of computed EIFs and develop a framework for cost-effective and accurate computation of EIFs by density functional theory (DFT). We generated two benchmark databases of experimentally determined EIFs, one for H isotopes and another for the isotopes of the heavy atoms C, N and O. The accuracy of several DFT exchange-correlation functionals in calculating EIFs was then evaluated by comparing the computational results to these experimental datasets. We find that with the def2-TZVP basis set, O3LYP had the lowest mean absolute deviation (21‰ and 3.9‰ for the isotopic fractionation of H and the heavier atoms, respectively), but the GGA/meta-GGA functionals τHCTH_D3BJ, τHCTH and HCTH have similar performances (22‰ and 4.1‰, respectively, for τHCTH_D3BJ). Leveraging the good performance of computationally efficient functionals, we provide a robust, practical, experimentally validated framework for using DFT to accurately predict EIFs of large organic molecules, including uncertainty estimates.

Those who died very young-Inferences from δ15 N and δ13 C in bone collagen and the absence of a neonatal line in enamel related to the possible onset of breastfeeding

OBJECTIVES

Stable isotope analysis has often been used in neonatal remains from archeological contexts to investigate the presence of a signal of breastfeeding and weaning in past populations. Tooth histology on the other hand might be used as an indicator of birth survival. This pilot study aimed to investigate the feasibility of using stable nitrogen (δ¹⁵ N) and carbon (δ¹³ C) isotope values from neonatal bone collagen to elucidate if values deviating from the adult female average could indicate breastfeeding and co-occur with the presence of a neonatal line (NNL). The combination of these independent indicators might be useful in clarifying the fate of individuals who died around birth.

MATERIALS AND METHODS

Bone collagen from 21 archeological human and animal specimens was extracted and analyzed via mass-spectrometry for δ¹⁵ N and δ¹³ C. A verification of the stable isotope results was undertaken using tooth histology on three individuals who were investigated for the presence of a NNL as an indicator of live birth and short survival.

RESULTS

The biological age of the human samples varied between 8.5 lunar months (Lm) and 2 postnatal months (Pm) of age. All except one individual exhibited elevated δ¹⁵ N values compared to the female average. The histological analyses revealed no NNL for this and two further individuals (n = 3).

DISCUSSION

The results indicate that elevated nitrogen values of very young infants relative to a female average in archeological contexts are not necessarily associated with a breastfeeding onset signal, and therefore cannot be used exclusively as a proxy of birth survival. The elevation might be possible due to various reasons; one could be nutritional, in particular maternal stress during pregnancy or a metabolic disorder of mother and/or her child. In those cases, the evaluation of a NNL might reveal a false breastfeeding signal as seen for two individuals in our sample who have elevated nitrogen values despite the fact no NNL could be observed. Overall, our data support the growing awareness that bone collagen δ¹⁵ N values of neonates/infants should not be used as a proxy for breastfeeding or birth survival on its own.

Comparing apples and oranges: Why infant bone collagen may not reflect dietary intake in the same way as dentine collagen

OBJECTIVES

Recent developments in incremental dentine analysis allowing increased temporal resolution for tissues formed during the first 1,000 days of life have cast doubt on the veracity of weaning studies using bone collagen carbon (δ13 C) and nitrogen (δ15 N) isotope ratio data from infants. Here, we compare published bone data from the well-preserved Anglo-Saxon site of Raunds Furnells, England, with co-forming dentine from the same individuals, and investigate the relationship of these with juvenile stature. The high-resolution isotope data recorded in dentine allow us to investigate the relationship of diet with juvenile stature during this critical period of life.

MATERIALS AND METHODS

We compare incremental dentine collagen δ13 C and δ15 N data to published bone collagen data for 18 juveniles and 5 female adults from Anglo Saxon Raunds Furnells alongside new data for juvenile skeletal and dental age. An improvement in the method by sampling the first 0.5 mm of the sub-cuspal or sub-incisal dentine allows the isotopic measurement of dentine formed in utero.

RESULTS AND DISCUSSION

δ13 C profiles for both dentine and bone are similar and more robust than δ15 N for estimating the age at which weaning foods are introduced. Our results suggest δ15 N values from dentine can be used to evaluate the maternal/in utero diet and physiology during pregnancy, and that infant dentine profiles may reflect diet PLUS an element of physiological stress. In particular, bone collagen fails to record the same range of δ15 N as co-forming dentine, especially where growth is stunted, suggesting that infant bone collagen is unreliable for weaning studies.

Wintertime stress, nursing, and lead exposure in Neanderthal children

Scholars endeavor to understand the relationship between human evolution and climate change. This is particularly germane for Neanderthals, who survived extreme Eurasian environmental variation and glaciations, mysteriously going extinct during a cool interglacial stage. Here, we integrate weekly records of climate, tooth growth, and metal exposure in two Neanderthals and one modern human from southeastern France. The Neanderthals inhabited cooler and more seasonal periods than the modern human, evincing childhood developmental stress during wintertime. In one instance, this stress may have included skeletal mobilization of elemental stores and weight loss; this individual was born in the spring and appears to have weaned 2.5 years later. Both Neanderthals were exposed to lead at least twice during the deep winter and/or early spring. This multidisciplinary approach elucidates direct relationships between ancient environments and hominin paleobiology.

The role of infant life histories in the construction of identities in death: An incremental isotope study of dietary and physiological status among children afforded differential burial

OBJECTIVES

Isotope ratio analyses of dentine collagen were used to characterize short-term changes in physiological status (both dietary status and biological stress) across the life course of children afforded special funerary treatment.

MATERIALS AND METHODS

Temporal sequences of δ¹⁵ N and δ¹³ C isotope profiles for incrementally forming dentine collagen were obtained from deciduous teeth of 86 children from four early-medieval English cemeteries. Thirty-one were interred in child-specific burial clusters, and the remainder alongside adults in other areas of the cemetery. Isotope profiles were categorized into four distinct patterns of dietary and health status between the final prenatal months and death.

RESULTS

Isotope profiles from individuals from the burial clusters were significantly less likely to reflect weaning curves, suggesting distinctive breastfeeding and weaning experiences. This relationship was not simply a factor of differential age at death between cohorts. There was no association of burial location neither with stage of weaning at death, nor with isotopic evidence of physiological stress at the end of life.

DISCUSSION

This study is the first to identify a relationship between the extent of breastfeeding and the provision of child-specific funerary rites. Limited breastfeeding may indicate the mother had died during or soon after birth, or that either mother or child was unable to feed due to illness. Children who were not breastfed will have experienced a significantly higher risk of malnutrition, undernutrition and infection. These sickly and perhaps motherless children received care to nourish them during early life, and were similarly provided with special treatment in death.

Let's talk about stress, baby! Infant-feeding practices and stress in the ancient Atacama desert, Northern Chile

AIMS AND OBJECTIVES

The transition to an agricultural economy is often presumed to involve an increase in female fertility related to changes in weaning practice. In particular, the availability of staple crops as complementary foods is hypothesized to allow earlier weaning in agricultural populations. In this study, our primary aim is to explore whether this model fits the agricultural transition in the Atacama Desert using incremental isotopic analysis. A secondary aim of this study is to identify isotopic patterns relating to weaning, and assess how these may be differentiated from those relating to early life stress.

MATERIALS AND METHODS

We use incremental isotopic analysis of dentine to examine changes in δ¹⁵ N and δ¹³ C values from infancy and childhood in sites of the Arica region (n = 30). We compare individuals from pre-agricultural and agricultural phases to establish isotopic patterns and relate these patterns to maternal diet, weaning trajectory and physiological stress.

RESULTS

We find that there is no evidence for systematic temporal or geographic variation in incremental isotopic results. Instead, results from all time periods are highly variable, with weaning completed between 1.5 and 3.5 years. Characteristics of the incremental profiles indicate that both in utero and postnatal stress were a common part of the infant experience in the Atacama.

DISCUSSION

In the Atacama Desert it appears that the arrival of agricultural crops did not result in uniform shifts in weaning behavior. Instead, infant and child diet seems to have been dictated by the broad-spectrum diets of the mothers, perhaps as a way of mitigating the stresses of the harsh desert environment.

Breastfeeding, weaning, and dietary practices during the Western Zhou Dynasty (1122-771 BC) at Boyangcheng, Anhui Province, China

OBJECTIVES

Here we investigate breastfeeding and weaning practices and adult dietary habits at the Western Zhou Dynasty (1122-771 BC) site of Boyangcheng () located in Anhui Province, China. In addition, we utilize the differences in bone collagen turnover rates between rib and long bones from the same individual to examine past life histories, such as changes in diet or residence.

MATERIALS AND METHODS

Bone collagen from both the rib and long bones (either femora or humeri) of 42 individuals was measured for stable isotope ratios of carbon (δ¹³ C) and nitrogen (δ¹⁵ N). In addition, δ¹³ C and δ¹⁵ N values are reported for 35 animals (dogs, cows, horses, pigs, and deer).

RESULTS

The human δ¹³ C values range from -20.7‰ to -12.0‰ with a mean value of -18.8 ± 1.6‰. The human δ¹⁵ N values range from 9.1‰ to 13.4‰ with a mean value of 10.9 ± 1.0‰. The animals display a wide range of δ¹³ C (-21.5‰ to -8.2‰; -15.8 ± 4.5‰) and δ¹⁵ N values (4.0‰ to 9.5‰; 6.5 ± 1.8‰).

CONCLUSIONS

The adult δ¹³ C and δ¹⁵ N results indicate that mixed C₃ (rice) and C₄ (millet) terrestrial diets with varying levels of animal protein (mostly pigs and deer) were consumed. The elevated subadult δ¹⁵ N results return to adult levels by approximately 3-4 years of age, indicating that the weaning process was completed during this period. Individuals between 2 and 10 years old, with lower δ¹³ C and δ¹⁵ N results than the adult mean, possibly consumed more plant-based diets, and this is consistent with Chinese medical teachings ∼1500 years later during the Tang Dynasty (AD 618-907). The isotopic offsets between the ribs and long bones revealed that five adults experienced dramatic dietary shifts in their later lives, switching from predominately C₃ /C₄ to C₃ diets. This research provides the first isotopic information about ancient Chinese breastfeeding and weaning practices and establishes a foundation for future studies to examine diachronic trends.

Post-weaning diet in archaeological human populations: A meta-analysis of carbon and nitrogen stable isotope ratios of child skeletons

OBJECTIVES

Childhood is a unique stage in human life history, in which subadults have completed their weaning process but are still dependent on older individuals for survival. Although the importance of food provisioning during childhood has been intensively discussed, childhood diet in the past has rarely been studied in a systematic manner.

METHODS

In this study, a meta-analysis of carbon and nitrogen stable isotope ratios of post-weaning children (PWC) in Holocene human populations around the world is presented. The isotope ratios of PWC were standardized with those of adult females and males in the same population, and they were analyzed in terms of the difference in subsistence.

RESULTS

Results of this study indicate that diets of PWC and adults were generally similar (most differences were within the range of ±1‰), which is consistent with the universal feature of food provisioning to PWC in humans. In hunter-gatherer populations, there is no significant difference between PWC and adult isotope ratios. In non-hunter-gatherer populations, however, PWC probably consumed significantly larger proportions of foods from lower trophic levels than did the adults, and such foods would be terrestrial C₃ plants.

CONCLUSIONS

Potential factors relating to the dietary differences among PWC and adults are presented from a perspective of balance between food provisioning and self-acquisition by PWC. Significant isotopic differences between PWC and adults in non-hunter-gatherer populations revealed in this study have implications for declined health during the subsistence transition in Holocene, isotopic studies using human tooth enamel, and "δ¹⁵ N dip" of subadults after weaning.

Assessing human weaning practices with calcium isotopes in tooth enamel

Weaning practices differ among great apes and likely diverged during the course of human evolution, but behavioral inference from the fossil record is hampered by a lack of unambiguous biomarkers. Here, we show that early-life dietary transitions are recorded in human deciduous tooth enamel as marked variations in Ca isotope ratios (δ^44/42Ca). Using a sequential microsampling method along the enamel growth axis, we collected more than 150 enamel microsamples from 51 deciduous teeth of 12 different modern human individuals of known dietary histories, as well as nine enamel samples from permanent third molars. We measured and reconstructed the evolution of ⁴⁴Ca/⁴²Ca ratios in enamel from in utero development to first months of postnatal development. We show that the observed variations of δ^44/42Ca record a transition from placental nutrition to an adult-like diet and that Ca isotopes reflect the duration of the breastfeeding period experienced by each infant. Typically, the δ^44/42Ca values of individuals briefly or not breastfed show a systematic increase during the first 5-10 mo, whereas individuals with long breastfeeding histories display no measurable variation in δ^44/42Ca of enamel formed during this time. The use of Ca isotope analysis in tooth enamel allows microsampling and offers an independent approach to tackle challenging questions related to past population dynamics and evolution of weaning practices in hominins.

Cyclical nursing patterns in wild orangutans

Nursing behavior is notoriously difficult to study in arboreal primates, particularly when offspring suckle inconspicuously in nests. Orangutans have the most prolonged nursing period of any mammal, with the cessation of suckling (weaning) estimated to occur at 6 to 8 years of age in the wild. Milk consumption is hypothesized to be relatively constant over this period, but direct evidence is limited. We previously demonstrated that trace element analysis of bioavailable elements from milk, such as barium, provides accurate estimates of early-life diet transitions and developmental stress when coupled with growth lines in the teeth of humans and nonhuman primates. We provide the first detailed nursing histories of wild, unprovisioned orangutans (Pongo abelii and Pongo pygmaeus) using chemical and histological analyses. Laser ablation inductively coupled plasma mass spectrometry was used to determine barium distributions across the teeth of four wild-shot individuals aged from postnatal biological rhythms. Barium levels rose during the first year of life in all individuals and began to decline shortly after, consistent with behavioral observations of intensive nursing followed by solid food supplementation. Subsequent barium levels show large sustained fluctuations on an approximately annual basis. These patterns appear to be due to cycles of varying milk consumption, continuing until death in an 8.8-year-old Sumatran individual. A female Bornean orangutan ceased suckling at 8.1 years of age. These individuals exceed the maximum weaning age reported for any nonhuman primate. Orangutan nursing may reflect cycles of infant demand that relate to fluctuating resource availability.

Alloparenting is associated with reduced maternal lactation effort and faster weaning in wild chimpanzees

Alloparenting, when individuals other than the mother assist with infant care, can vary between and within populations and has potential fitness costs and benefits for individuals involved. We investigated the effects of alloparenting on the speed with which infants were weaned, a potential component of maternal fitness because of how it can affect inter-birth intervals, in wild chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Uganda. We also provide, to our knowledge, the first description of alloparenting in this population and present a novel measure of the contribution of milk to infant diets through faecal stable nitrogen isotopes (δ15N). Using 42 mother-infant pairs, we tested associations of two alloparenting dimensions, natal attraction (interest in infants) and infant handling (holding, carrying), to the proportion of time mothers spent feeding and to maternal lactation effort (mean nursing rates and mother-infant δ15N differences). Neither natal attraction nor infant handling was significantly associated with feeding time. Infant handling was inversely associated with both measures of lactation effort, although natal attraction showed no association. Alloparenting may benefit mothers by enabling females to invest in their next offspring sooner through accelerated weaning. Our findings emphasize the significance of alloparenting as a flexible component of female reproductive strategies in some species.

Weaning practices among pastoralists: New evidence of infant feeding patterns from Bronze Age Eurasia

OBJECTIVES

This paper investigates infant feeding practices through stable carbon (δ¹³ C) and nitrogen (δ¹⁵ N) isotopic analyses of human bone collagen from Kamennyi Ambar 5, a Middle Bronze Age cemetery located in central Eurasia. The results presented are unique for the time period and region, as few cemeteries have been excavated to reveal a demographic cross-section of the population. Studies of weaning among pastoral societies are infrequent and this research adds to our knowledge of the timing, potential supplementary foods, and cessation of breastfeeding practices.

MATERIALS AND METHODS

Samples were collected from 41 subadults (<15 years) and 27 adults (15+ years). Isotopic reference sets from adult humans as well as faunal remains were utilized as these form the primary and complementary foods fed to infants.

RESULTS

Slight shifts in δ¹³ C and δ¹⁵ N values revealed that weaning was a multi-stage process (breastfeeding, weaning, and complete cessation of nursing) that began at 6 months of age, occurred over several years of early childhood, and was completed by 4 years of age.

DISCUSSION

Our results indicate that weaning was a multi-stage process that was unique among late prehistoric pastoralist groups in Eurasia that were dependent on milk products as a supplementary food. Our discussion centers on supporting this hypothesis with modern information on central and east Eurasian herding societies including the age at which complementary foods are introduced, the types of complementary foods, and the timing of the cessation of breastfeeding. Integral to this work is the nature of pastoral economies and their dependence on animal products, the impact of complementary foods on nutrition and health, and how milk processing may have affected nutrition content and digestibility of foods. This research on Eurasian pastoralists provides insights into the complexities of weaning among prehistoric pastoral societies as well as the potential for different complementary foods to be incorporated into infant diets in the past.

A novel fecal stable isotope approach to determine the timing of age-related feeding transitions in wild infant chimpanzees

OBJECTIVES

Determining nutritional development in wild primates is difficult through observations because confirming dietary intake is challenging. Physiological measures are needed to determine the relative contributions of maternal milk and other foods at different ages, and time of weaning. We used fecal stable carbon and nitrogen isotopes (δ¹³ C, δ¹⁵ N) and fecal nitrogen concentrations (%N) from wild chimpanzees at Ngogo, Uganda, to derive physiological dietary indicators during the transition from total reliance on maternal milk to adult foods after weaning.

MATERIALS AND METHODS

We analyzed 560 fecal samples collected non-invasively from 48 infants, their mothers, and 6 juvenile siblings. Most infant and juvenile samples (90%) were matched to samples collected from mothers on the same day. Isotopic assessments were compared with observations of nursing and feeding.

RESULTS

Infants ≤1 year old showed average δ¹⁵ N, δ¹³ C and %N ratios that were 2.0‰, 0.8‰ and 1.3% greater than their mothers, respectively, interpreted as trophic level effects. Although data collected on newborns were few, results suggest that solid foods were consumed within 2-5 months after birth. Trophic level differences decreased steadily after 1 year, which indicates a decreasing relative contribution of milk to the diet. Isotopic results indicated infants were weaned by 4.5 years old-more than a year earlier than observations of nipple contacts ceased, which revealed the occurrence of "comfort nursing." Juvenile isotopic signatures indicate no nursing overlap between siblings.

DISCUSSION

Our results resemble the stable isotope differences of human babies. This study contributes to a model of chimpanzee nutritional development required to understand early life history patterns in hominins.

Jealousy Protest

In this article, nascent jealousy’s ultimate foundation is theorized as an adapted psychological mechanism that evolved in the environment of evolutionary adaptedness (EEA) to prepare 1-year-olds for defending against premature weaning upon the closely spaced birth of a sibling. This position rests on evidence that nascent jealousy is expressed through jealousy protest, a constellation of caregiver-directed protests and bids for exclusive attention, and evidence that its onset occurs at approximately 9 months of age. Given that the period of human gestation is 9 months, we propose that jealousy protest’s form and timing were compelled by the possibility that the end of an infant’s first year could be met by competition with a newborn sibling. That possibility placed infants at risk of malnutrition and mortality due to entailing the loss of exclusive access to mother’s milk, while infants were at an age when they were still heavily reliant on breast milk for survival. At this juncture, threat posed by the birth of a sibling was compounded by conditions of the EEA, where the sole viable source of breast milk was an infant’s mother, and her supply of milk was sufficient for sustaining only one child at a time. We conclude by offering suggestions for future research and discuss implications for the theory of parent–offspring conflict as a foundation of adaptations in children.

Isotopic evidence of human mobility and diet in a prehistoric/protohistoric Fijian coastal environment (c. 750-150 BP)

OBJECTIVES

Bourewa, on the southwest coast of Viti Levu in Fiji, is a multi-period site that contained burials dated to the later Vuda Phase (750-150 BP), a period of climatic fluctuations that potentially impacted the availability of food resources. We aim to investigate diet and movement at this site during a time of possible ecological pressure and political change.

MATERIALS AND METHODS

We analyzed δ(13) C, δ(15) N, and (87) Sr/(86) Sr of these Vuda Phase individuals (n = 25) interred at the site. By analyzing dentin and bone, both childhood diet and the diet within the past few years of adults' lives were examined.

RESULTS

The paleodietary results suggested that adult diets consisted largely of low trophic level marine organisms. Dentin and bone isotopic values differed significantly: childhood diet involved consumption of more higher trophic level terrestrial foods. Most individuals displayed (87) Sr/(86) Sr ratios expected of people living along a marine coastline. However, a few individuals displayed (87) Sr/(86) Sr ratios and paleodietary values (δ(13) Cdentin , δ(15) Ndentin ) suggestive of living further inland or consuming a more terrestrial-based childhood diet.

DISCUSSION

The results are compared with past studies of sites from Fiji and nearby archipelagoes, placing our interpretations into a wider regional context. The Bourewa community appears to have consumed more low trophic level marine foods than any nearby site, possibly because terrestrial foods were more difficult to acquire. Interpreting the childhood diet is challenging due to the paucity of ethnohistoric literature on Fijian childhood; small meals outside of communal mealtimes or feeding children terrestrial animal protein as a means of cultural buffering are potential explanations.