Galbany Jordi, Muhire Thadée, Vecellio Veronica, Mudakikwa Antoine, Nyiramana Aisha, Cranfield Michael R, Stoinski Tara S, McFarlin Shannon C
Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, District of Columbia.
Department of Social Psychology and Quantitative Psychology, University of Barcelona, Barcelona, Spain.
Am J Phys Anthropol. 2018 Dec;167(4):930-935. doi: 10.1002/ajpa.23720. Epub 2018 Oct 23.
Ecological factors, but also tooth-to-tooth contact over time, have a dramatic effect on tooth wear in primates. The aim of this study is to test whether incisor tooth wear changes predictably with age and can thus be used as an age estimation method in a wild population of mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda.
In mountain gorillas of confidently known chronological age (N = 24), we measured the crown height of all permanent maxillary and mandibular incisors (I , I , I , I ) as a proxy for incisal macrowear. Linear and quadratic regressions for each incisor were used to test whether age can be predicted by crown height. Using these models, we then predicted age at death of two individual mountain gorillas of probable identifications, based on their incisor crown height.
Age decreased significantly with incisor height for all teeth, but the upper first incisors (I ) provided the best results, with the lowest Akaike's Information Criterion corrected for small sample size (AICc) and lowest Standard Error of the Estimate (SEE). When the best age equations for each sex were applied to gorillas with probable identifications, the predicted ages differed 1.58 and 3.33 years from the probable ages of these individuals.
Our findings corroborate that incisor crown height, a proxy for incisal wear, varies predictably with age. This relationship can be used to estimate age at death of unknown gorillas in the skeletal collection, and in some cases, to corroborate the identity of individual gorillas recovered from the forest postmortem at an advanced state of decomposition. Such identifications help fill gaps in the demographic database and support research that requires individual-level data.
生态因素以及牙齿间长期的接触，对灵长类动物的牙齿磨损都有显著影响。本研究的目的是测试门齿磨损变化是否随年龄呈可预测性变化，从而能否作为一种年龄估计方法，应用于卢旺达火山国家公园野生山地大猩猩（Gorilla beringei beringei）种群。
在已知确切年龄的山地大猩猩（N = 24）中，我们测量了所有上颌和下颌恒门齿（I1、I2、I3、I4）的冠高，以此作为切牙宏观磨损的指标。对每颗门齿进行线性和二次回归分析，以测试冠高是否能预测年龄。然后，利用这些模型，根据两只可能已识别身份的山地大猩猩的门齿冠高，预测它们的死亡年龄。
所有牙齿的年龄均随门齿高度显著降低，但上颌第一门齿（I1）的结果最佳，其校正小样本量的赤池信息准则（AICc）最低，估计标准误差（SEE）也最低。当将每种性别的最佳年龄方程应用于可能已识别身份的大猩猩时，预测年龄与这些个体的可能年龄相差1.58年和3.33年。
我们的研究结果证实，作为切牙磨损指标的门齿冠高随年龄呈可预测性变化。这种关系可用于估计骨骼样本中未知大猩猩的死亡年龄，在某些情况下，还可用于证实从森林中回收的处于高度腐烂状态的个体大猩猩的身份。此类身份识别有助于填补人口统计学数据库中的空白，并支持需要个体水平数据的研究。
