Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Laboratorio de Ecología Evolutiva Humana (LEEH), Unidad de Enseñanza Universitaria Quequén, Facultad de Ciencias Sociales, Universidad Nacional del Centro de la Provincia de Buenos Aires (UNCPBA), Argentina; School of Biological Sciences, University of Utah, USA.
School of Biological Sciences, University of Utah, USA.
Forensic Sci Int. 2021 Oct;327:110990. doi: 10.1016/j.forsciint.2021.110990. Epub 2021 Sep 2.
Accurate human provenancing using stable isotopes depends directly on solid understandings of the geographic and individual factors affecting isotope variability and incorporation into human tissues. Transfer of isotopic, and therefore spatial, information between environmental water and biological tissues is mediated by the isotopic composition of body water. Thus, there is a need to study body water isotope ratios at a population level and over a large isotopic and geographic range. We evaluated oxygen (δO) and hydrogen (δH) isotope values of body water from 72 volunteers in 10 different cities across the US, and over a 5-10-day period. We analyzed covariates (e.g., water intake, physical activity, biometrics, gender) that might explain individual stable isotope ratio variations and tested a predictive model that incorporates the δ-values of drinking water, food, and O as well as individual variables to predict the δ-values of body water. The individual variability in body water isotope values overtime (mean 0.3‰ for δO and 2.3‰ for δH) was lower than the intra-city variability (mean 0.9‰ for δO and 6.9‰ for δH). Body water isotope values differed among cities (ANOVA: δOF = 97.2, p < 0.001; δHF = 176.2, p < 0.001). However, significant overlap among some cities with different drinking water was discovered. We detected significant covariation of measured drinking water and human body water isotope values (both isotope systems R ≥ 0.89, p < 0.001) and small but significant effects of the average daily exercise and amount of fluid intake. The differences between measured and model-predicted body water values (mean 0.12 ± 1.2‰ for ΔδO and -1.2 ± 8.2‰ for ΔδH) were statistically indistinguishable from zero (ΔδO t = -0.751, p = 0.45; ΔδH t = 1.133, p = 0.26). Here we show that community level variation exists in the δO and δH values and the primary drivers are the regional differences in drinking water isotopes. Consistency of the body water isotope composition over the study period suggests that tissues would incorporate a stable isotope signal over time. The amount of drinking water and physical activity influence body water values, while the variation in the isotopic values of food may contribute to regional level variability, but that still remains to be assessed further. The human body water model provides accurate estimates for measured values, capturing and reproducing the main features of the body water isotope variation across space.
利用稳定同位素进行准确的人类起源研究，直接依赖于对影响同位素变异和纳入人体组织的地理和个体因素的深入了解。环境水和生物组织之间同位素的转移，也就是空间信息的转移，由体液的同位素组成所介导。因此，有必要在人群水平上并在较大的同位素和地理范围内研究体液同位素比值。我们评估了美国 10 个不同城市的 72 名志愿者在 5-10 天期间的体液中的氧（δO）和氢（δH）同位素值。我们分析了可能解释个体稳定同位素比值变化的协变量（例如，水的摄入量、体力活动、生物统计学、性别），并测试了一个预测模型，该模型将饮用水、食物和 O 的 δ 值以及个体变量纳入其中，以预测体液的 δ 值。个体随时间变化的体液同位素值的个体差异（δO 的平均值为 0.3‰，δH 的平均值为 2.3‰）低于城市内的变异性（δO 的平均值为 0.9‰，δH 的平均值为 6.9‰）。城市之间的体液同位素值存在差异（方差分析：δOF=97.2，p<0.001；δHF=176.2，p<0.001）。然而，发现一些具有不同饮用水的城市之间存在显著重叠。我们检测到测量的饮用水和人体体液同位素值之间存在显著的协变（两个同位素系统的 R 值均≥0.89，p<0.001），以及日常锻炼和液体摄入量的平均值的小但显著的影响。测量值和模型预测的体液值之间的差异（ΔδO 的平均值为 0.12±1.2‰，ΔδH 的平均值为-1.2±8.2‰）在统计学上与零无差异（ΔδO t=-0.751，p=0.45；ΔδH t=1.133，p=0.26）。在这里，我们表明社区层面存在 δO 和 δH 值的变化，主要驱动因素是饮用水同位素的区域差异。研究期间体液同位素组成的一致性表明，组织会随时间积累稳定同位素信号。饮用水量和体力活动影响体液值，而食物同位素值的变化可能导致区域水平的变异性，但这仍有待进一步评估。人体体液模型为测量值提供了准确的估计，捕获并再现了空间内体液同位素变化的主要特征。
