Deeper or more 'severe' linear enamel hypoplasia (LEH) defects are hypothesized to reflect more severe stress during development, but it is not yet clear how depth is influenced by intrinsic enamel growth patterns. Recent work documented inter- and intraspecific differences in LEH defect depth in extant great apes, with mountain gorillas having shallower defects than other taxa, and females having deeper defects than males. Here, we assess the correspondence of inter- and intraspecific defect depth and intrinsic aspects of enamel growth: enamel extension rates, outer enamel striae of Retzius angles, and linear enamel thickness. Thin sections of great ape canines (n = 40) from Gorilla beringei beringei, Gorilla gorilla gorilla, Pan troglodytes, and Pongo spp. were analyzed. Enamel extension rates were calculated within deciles of enamel-dentine junction length. Linear enamel thickness and the angle of intersection between striae of Retzius and the outer enamel surface were measured in the imbricational enamel. Mountain gorillas have faster enamel extension rates and shallower striae angles than the other taxa examined. Mountain gorillas have thinner imbricational enamel than western lowland gorillas and orangutans, but not chimpanzees. In the combined-taxon sample, females exhibit larger striae angles and thicker imbricational enamel than males. Enamel extension rates are highly negatively correlated with striae angles and LEH defect depth. Enamel growth variation corresponds with documented inter- and intraspecific differences in LEH defect depth in great ape canines. Mountain gorillas have shallower striae angles and faster extension rates than other taxa, which might explain their shallow LEH defect morphology and the underestimation of their LEH prevalence in previous studies. These results suggest that stressors of similar magnitude and timing might produce defects of different depths in one species or sex vs. another, which has implications for interpretations of stress histories in hominins with variable enamel growth patterns.

中文翻译：

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更快的生长与大猿犬中较浅的线性发育不良有关。

据推测，更深或更严重的“线性”釉质发育不全（LEH）缺陷反映了发育过程中更严重的压力，但尚不清楚内在的釉质生长方式如何影响深度。最近的工作表明，在现存的大猿猴中，LEH缺陷深度的种间和种内差异，山地大猩猩的缺陷比其他类群浅，雌性的缺陷比雄性深。在这里，我们评估种间和种内缺陷深度与搪瓷生长的内在方面的对应关系：搪瓷延伸率，Retzius角的外部搪瓷条纹和线性搪瓷厚度。大猩猩犬（n = 40）的薄片，来自大猩猩大猩猩，大猩猩大猩猩，盘尾猿和Pongo spp。被分析。牙釉质延伸率是在牙釉质-牙本质交界长度的十分之一内计算的。测量了在搪瓷搪瓷中的线性搪瓷厚度和Retzius条纹与搪瓷外表面之间的相交角。山地大猩猩的牙釉质扩展速度更快，条纹角度更浅。山地大猩猩比西部低地大猩猩和猩猩具有更薄的可吸收牙釉质，但黑猩猩则没有。在组合分类单元样本中，雌性显示出比雄性更大的条纹角和更厚的可浸润珐琅质。釉质延伸率与条纹角和LEH缺陷深度高度负相关。搪瓷生长变化与大猿犬的LEH缺损深度的种间和种内差异有对应关系。与其他类群相比，山地大猩猩的纹层角更浅，延伸速度更快，这可能解释了它们的浅层LEH缺陷形态和对先前研究中低层LEH患病率的低估。这些结果表明，大小和时间相近的应激源可能在一个物种或性别与另一物种或性别中产生不同深度的缺陷，这对于解释具有可变牙釉质生长模式的人源蛋白的应激历史具有重要意义。