Data for Study.

In living primates, bite forces required to fracture hard-object foods can result in high frequencies of chipped teeth, providing a comparative basis for inferring hard-object feeding in the fossil record. Yet, inferring hard-object feeding from chipping frequencies is complicated by factors such as dental wear, age, and sex that might also affect them. Using dental remains of rhesus macaques (Macaca mulatta) from Cayo Santiago, Puerto Rico, we investigated whether these factors covaried with molar chipping frequencies. We hypothesized that dental wear, because it has a direct relationship to chip formation, would be a stronger predictor of chipping frequencies than age. We also hypothesized that if a sex difference were found, males would have higher frequencies of chipping than females, which is the most common sex difference in chipping found in humans. Samples consisted of 36–38 molars from females and 60–63 molars from males per molar type. Dental wear was measured and chips were identified on consistently oriented occlusal surface photographs. We performed a logistic General Linear Mixed Model (GLMM) of chipping with data on wear and chipping for the six different molar types treated as repeated measures for individuals. The GLMM revealed statistically significant effects for wear and sex, but not for age, on chipping. Our results suggest that wear has a greater effect on chipping frequencies than age, and that sex, at least in this sample, can also affect chipping frequencies. Sex differences in chipping frequencies of the magnitude found here could potentially obscure dietary signals inferred from chipping in studies of fossil primates. These findings suggest that analyzing chipping frequencies with respect to wear and sex could help improve the accuracy of dietary reconstruction of fossil primate diets based on chipping.

现生灵长类动物中，碎裂硬质食物所需的咬合力会导致牙齿崩缺的发生频率显著升高，这为通过化石记录推断古灵长类的硬质食物摄食行为提供了比较学依据。然而，仅通过牙齿崩缺频率推断硬质食物摄食行为时，会受到诸多因素的干扰——诸如牙齿磨损、年龄与性别等，这些因素同样会对牙齿崩缺的发生产生影响。本研究以采自波多黎各卡约圣地亚哥岛的恒河猴（Macaca mulatta）颌骨遗骸为研究材料，探究上述因素是否与臼齿崩缺频率存在共变关系。我们提出两项研究假设：其一，鉴于牙齿磨损与牙崩缺的形成存在直接关联，其对崩缺频率的预测能力应强于年龄；其二，若研究发现性别差异，雄性个体的崩缺频率应高于雌性——这也是人类中已被证实的最为普遍的牙崩缺性别差异模式。本研究的样本涵盖各臼齿类型的雌性个体臼齿36~38颗、雄性个体臼齿60~63颗。研究人员通过拍摄标准化朝向的咬合面照片，对牙齿磨损程度进行量化，并识别牙崩缺痕迹。我们针对6种臼齿类型构建了牙崩缺的logistic广义线性混合模型（General Linear Mixed Model, GLMM），将个体内的不同臼齿作为重复测量项。该模型分析结果显示，牙齿磨损与性别对牙崩缺均具有显著的统计学效应，而年龄则未表现出此类效应。本研究结果表明，牙齿磨损对崩缺频率的影响程度高于年龄，且至少在本样本中，性别同样会对崩缺频率产生影响。本研究发现的性别差异幅度，可能会在古灵长类动物的牙崩缺饮食推断研究中掩盖其真实的饮食信号。上述研究结果提示，结合牙齿磨损与性别因素分析牙崩缺频率，有助于提升基于牙崩缺推断的古灵长类动物饮食重建的准确性。