Abstract
Integrated developmental and elemental information in teeth provide a unique framework for documenting breastfeeding histories, physiological disruptions, and neurotoxicant exposure in humans and our primate relatives, including ancient hominins. Here we detail our method for detecting the consumption of mothers' milk and exploring health history through the use of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) mapping of sectioned nonhuman primate teeth. Calcium-normalized barium and lead concentrations in tooth enamel and dentine may reflect milk and formula consumption with minimal modification during subsequent tooth mineralization, particularly in dentine. However, skeletal resorption during severe illness, and bioavailable metals in nonmilk foods, can complicate interpretations of nursing behavior. We show that explorations of the patterning of multiple elements may aid in the distinction of these important etiologies. Targeted studies of skeletal chemistry, gastrointestinal maturation, and the dietary bioavailability of metals are needed to optimize these unique records of human health and behavior.
Highlights
Tooth growth and mineralization: a microscopic archive of developmental informationTeeth are one of the most common anatomical units recovered in forensic, archeological, and paleontological contexts
Nursing infants absorb Ca passively prior to the maturation of their GI tract, a process that is enhanced by other chemicals in mothers’ milk. This dynamic process of Ca transportation is relevant to studies of infant nursing and metals exposure, as Ca shares several chemical characteristics with the “bone-seeking” elements barium, strontium, and lead
The neonatal line in human and nonhuman primate deciduous teeth and permanent first molar (M1) provides a reliable biomarker for the estimation of an individual’s age as well as their nursing history, including reliance on artificial infant formulas (Figure 3).[18]. By using this unique skeletal birth certificate as a focal point, we have shown that the continuous process of tooth mineralization does not greatly obscure the timing of known dietary transitions, and instead records the onset of nursing through an increase in Ba, as well as the end of milk intake through a decrease of Ba, which is discussed further below
Summary
Tooth growth and mineralization: a microscopic archive of developmental information. Teeth are one of the most common anatomical units recovered in forensic, archeological, and paleontological contexts. Additional ions are added through active transport and diffusion, with dentine reaching a fully mineralized state more rapidly than enamel.[19,23] Once enamel secretory cells reach their final position at the tooth surface, hydroxyapatite crystals further thicken with the active addition of calcium and phosphate, and the removal of water and proteins This final stage of enamel mineralization (maturation) does not follow the original pattern of matrix secretion that produces incremental features, leading to distinct spatial patterns of elemental incorporation.[22,25] Dentine forms in tandem with enamel but continues beyond it, forming the bulk of the tooth root while retaining more protein and fluid as a result of its relatively rapid mineralization.[23,26]. We show how the timing and patterning of these elements in nonhuman primate teeth provide retrospective access to consequential behaviors for human survival, reproduction, and health outcomes
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