Breastfeeding and weaning in ancient populations

As one of the unique features of the human life history, breastfeeding is key area of research on past human populations. Infant feeding practices have important implications not only for the health, growth, and development of children, but also for population dynamics, as they affect fertility, morbidity, and mortality patterns. More importantly, human breastfeeding and weaning practices (BWP) are variable and shaped by complex interactions of the cultural and biological givens of any human group, from availability of nutrition and associated beliefs, to the ways in which any group constructs childhood and parenthood in the context of its ideological superstructures. When the unique human pattern emerged, and what the drivers of this variation are, remain open questions for bioarchaeologists. With current differences in expert opinion as to the proper timing for the introduction of solids into an infant's diet, examining past human practices on a larger scale allows us to better evaluate our guidelines and understand whether a “natural pattern” of breastfeeding for humans even exists. Since the discovery that the nitrogen stable isotope ratio (δ15N) in body tissues can be used to reconstruct breastfeeding and weaning practices (Fogel, Tuross, & Owsley, 1989), there have been numerous studies aimed at developing more precise methods of reconstructing BWPs in archaeological populations. While most early studies have concentrated on stable carbon (δ13C) and nitrogen isotopes, later approaches have incorporated new elements such as oxygen (δ18O), and more recently sulfur (δ34S), in order to gain resolution around important questions related to the age at the start of weaning and the type of resources used during the weaning process. Most early isotope studies on this topic failed to consider, differential bone turnover rates in juveniles, thus affecting the reliability of interpretations of BWP. Studies that use a direct comparison of the nitrogen isotope composition of adult females and juvenile individuals to infer the start of weaning and the cessation of breastfeeding often employ static isotopic enrichment factors between different food sources and adult female tissue (bone collagen), adult female tissue and breast milk, and non-adult mixed diet (milk and non-milk) and their tissues (Reynard & Tuross, 2015). Other approaches normalize non-adult values by subtracting the adult (or adult female) mean from juvenile values; however, as we know, these do not necessarily represent the mothers who are providing milk. The quantitative evaluation of contributions from breast milk, weaning foods, and adult foods in the non-adults' diet requires knowledge of physiological processes, as food components are represented in body tissues in proportions that are not necessarily equal to the proportion consumed. Importantly, studies have also detected diet-specific variations in the diet-collagen fractionation factors, suggesting that the exact dietary offsets (∆δ13Cdiet-col) are influenced by the isotopic compositions of the macronutrients consumed (Froehle, Kellner, & Schoeninger, 2010), which could lead to the misrepresentation of the weaning foods consumed if static isotopic offsets are used. Finally, most previous studies assumed that each individual in the population had a similar “weaning trajectory” to the population average and analyse cross-sectional samples of skeletal populations (concentrating on non-adults of different ages). These studies may underestimate the individual heterogeneity in the risk of death and disease. This results in an “osteological paradox,” as skeletal series represents only dead individuals who did not survive past the age at which they are examined (Wood, Milner, Harpending, & Weiss, 1992), and thus are not necessarily representative of the actual health status and life history of the population. This Special Issue of the International Journal of Osteoarchaeology brings together a selection of syntheses, regional studies, and papers with novel methodological approaches and techniques that offer suitable solutions for many of the challenges mentioned above. The use of Bayesian methods, such as the WARN model (Tsutaya & Yoneda, 2013), can provide probabilistic assessment of the timing of weaning, offering an alternative solution to the use of static offsets, bone turnover in non-adults, isotopic offsets between diet-tissues and tissues-milk, and collagen fractionation factors. In addition, most papers from this volume used serial sections of dentin from adults to reconstruct BWP, two of them with refined sampling protocols. By studying the teeth of adults—the individuals who survived the weaning process—it is possible to mimic a longitudinal study, assess the heterogeneity of risk, and account for the osteological paradox. The combination of stable isotopes with other lines of evidence also strength the reconstruction of BWP to better understand the variability of the isotopic signal among non-adults. Manuscripts included to this compilation cover a wide geographic and temporal distribution, thus allowing us to examine biological and cultural determinants of BWP in humans, including such factors as environment, subsistence strategies, sex-based differences, cultural perceptions, and lifestyle. We envision that these explorations, together with a critical analysis of the sustained uncertainties involved in reconstructing the BWP in ancient cultures, will serve as a reference point for future developments in the field. Ultimately, we hope that such analysis will enhance our understanding of complex relationships between breastfeeding and culture in humans

Archaeology · Breastfeeding · Developmental psychology · Environmental health · Geography · Population · Sociology · Weaning · Craniofacial Disorders and Treatments · Demography · Forensic Anthropology and Bioarchaeology Studies · Indigenous Studies and Ecology · Medicine · Psychology · Pediatrics

• Prácticas de crianza desde la perspectiva bioarqueológica

  Open Access•Bibiana Cadena Duarte, Bibiana Cadena-Duarte•Boletín de Antropología•2020

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• Tracing early life histories from Roman times to the Medieval era

  Open Access•Maren Velte, A Czermak et al.•Archaeological and Anthropological…•2023

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• Quantitative Reconstruction of Weaning Ages in Archaeological Human Populations Using Bone Collagen Nitrogen Isotope Ratios and Approximate Bayesian Computation

  Open Access•T Tsutaya, Minoru Yoneda et al.•PLoS ONE•2013

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• Focus

  Open Access•Andrew W Froehle, Corina M Kellner et al.•Journal of Archaeological Science•2010

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• The known, the unknown and the unknowable

  Open Access•Linda M Reynard, N Turo et al.•Journal of Archaeological Science•2014

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• The Osteological Paradox

  James W Wood, G R Milner et al.•Current Anthropology•1992

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