Abstract
This paper explores the potential of combining different isotope systems from different tissues to improve resolution when reconstructing breastfeeding and weaning practices (BWP) in archaeology. Additionally, we tested whether changes in diet can be detected in deciduous teeth. Rib collagen samples from 22 infants/children from the archaeological site of Bacuranao I (Mayabeque, Cuba) were processed for nitrogen (δ15N) and carbon (δ13Cco) stable isotopes and assessed using a Bayesian model (WARN). In addition, enamel of 48 teeth from 30 infants/children were analyzed for oxygen (δ18Oen) and carbon (δ13Cen) stable isotopes. Data revealed that the timing of weaning cannot be characterized precisely by analyzing either δ18O or δ15N. While a depletion in both δ15N and δ13Cco is only evident after one year, the WARN model suggested that the weaning process started at around 3 months and ended around 1.7 years. Most teeth were enriched in δ18Oen compared to deciduous incisors, suggesting a breastfeeding signal. However, a high variability in δ18O was found between similar teeth from the same individuals. Higher enrichment in δ18Oen, and variability, was observed in tissues formed during the first six months of life. A δ13C enrichment of 1.0‰ was observed among deciduous teeth and ribs. While most individuals enriched in δ15N showed enrichment in δ13C, the δ18O values were more variable. Our data suggests that stable isotopes of deciduous teeth, especially δ13Cen, can be used to detect changes in diet during the weaning process. It is also possible that the δ18O enrichment observed in M1 is influenced by the effects of cooking techniques on weaning foods. The combination of multiple isotope systems and tissues overcome some of the limitations posed by single tissue approaches.
Highlights
Combining multiple stable isotope systems in different tissues from the same individuals showed potential for both understanding the possible sources of intra-population variability, and refining the resolution at which events related to the weaning process can be detected in archaeological populations
While the WARN model predicts that the age at the start of weaning occurred at around four months of age (MDE = 0.3 years), most non-adult tissues formed until one year of age are still enriched in both δ15N and δ18O, suggesting that breastmilk was the most important protein [25,26,27] and water source [36, 80] in their diets during that time
Some infants younger than a year showed no signal of breastfeeding when comparing their δ15N and δ18O values with the estimated female baseline, suggesting that external food supplements and water were introduced into their diet, even before six months. This apparent disagreement between WARN model parameters and the visual inspection of the data (e.g., Fig 3) can be influenced by several factors, including the input of the low δ15N values observed in the collagen of some infants who died before six months of age into the WARN model, an artifact of the inaccuracy of the female δ15N and δ18O estimated values used as a baseline, or a time lag of δ15N values due to turnover rates, a factor that the WARN model does incorporate to estimate its parameters [24]
Summary
Refining models to reconstruct breastfeeding and weaning practices (BWPs) of past populations is of great interest to bioanthropologists, as it provides information about demographic. Combining multiple isotope systems from multiple non-adult tissues to detect the timing of weaning. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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