ABSTRACT

Dental enamel represents an important mineralized archive of an individual’s early life. Previously, isotopic (Ca) or trace element ratios (Sr/Ca, Ba/Ca) have been used to reveal dietary and weaning histories, although few studies have utilized both proxies to evaluate the respective results. Here we report histologically-defined, spatially-resolved Ca-isotope (laser-cut & TIMS) and trace element ratio (Sr/Ca, Ba/Ca; LA-ICPMS) profiles along the enamel-dentine-junction in three deciduous dental crowns of three early twentieth century Italian infants (Modern-22, 27, 29). Modern-27 and Modern-29 display overall similar patterns of Ca-isotope variation and reflect an overall increase of >1.0‰ in δ^44/40Ca across and after birth. Whilst the Sr/Ca and Ba/Ca signals of Modern-27 suggest a mixed breast-formula feeding, the two elemental proxies in Modern-29 hint at nearly exclusive breastfeeding until ∼4 months, followed by introduction of formula. A ∼0.5‰ δ^44/40Ca decrease across and after birth together with Sr/Ca ratios in Modern-22 suggest a dominant breastfeeding history for the first ∼5–8 months. Enamel Ca-isotope data alone are not sufficient to distinguish between breastfed or formula-fed infants. In addition, Ca-isotope profiles in deciduous enamel suggest a connection between prominent physiological stress like birth and negative Ca-isotope excursions, underlining the physiological overprint of Ca-isotope signatures.

摘要

牙釉质代表了个人早期生活的重要矿化档案。以前，同位素 (Ca) 或微量元素比率 (Sr/Ca, Ba/Ca) 已被用于揭示饮食和断奶历史，尽管很少有研究利用这两种代理来评估各自的结果。在这里，我们报告了三个落叶牙冠中沿釉质-牙本质-交界处的组织学定义、空间分辨的 Ca 同位素（激光切割和 TIMS）和微量元素比（Sr/Ca、Ba/Ca；LA-ICPMS）分布三名二十世纪早期的意大利婴儿（Modern-22, 27, 29）。Modern-27 和 Modern-29 显示出总体相似的 Ca 同位素变化模式，并反映δ ^{44/40的总体}增加> 1.0‰出生后和出生后的钙。虽然 Modern-27 的 Sr/Ca 和 Ba/Ca 信号表明混合母乳喂养，但 Modern-29 中的两个元素代理暗示几乎完全母乳喂养到 4 个月，然后引入配方奶。在 Modern-22 中，出生前后和出生后∼0.5 ‰ δ ^44/40 Ca减少以及 Sr/Ca 比率表明前 5-8 个月的母乳喂养史占主导地位。牙釉质钙同位素数据不足以区分母乳喂养或配方奶喂养的婴儿。此外，落叶牙釉质中的 Ca 同位素分布表明，出生等显着生理压力与负 Ca 同位素偏移之间存在联系，强调了 Ca 同位素特征的生理叠印。