Enamel thickness remains an important morphological character in hominin systematics and is regularly incorporated into dietary reconstructions in hominin species. We expand upon a previous study of enamel thickness in mandibular molars by examining a large maxillary molar sample of Plio-Pleistocene hominins (n = 62) and a comparative sample of extant nonhuman apes (n = 48) and modern humans (n = 29). 2D mesial planes of section were generated through microtomography, and standard dental tissue variables were measured to calculate average enamel thickness (AET) and relative enamel thickness (RET). AET was also examined across the lingual, occlusal, and buccal regions of the crown. This study confirms previous findings of increasing enamel thickness throughout the Plio-Pleistocene, being thinnest in Australopithecus anamensis and peaking in Australopithecus boisei, with early Homo specimens, exhibiting intermediate enamel thickness. Agreeing with previous findings, 2D plane of section enamel thickness is found to be a poor taxonomic discriminator, with no statistically significant differences observed between fossil hominins. For fossil hominins, modern humans, and Pongo, the occlusal region of enamel was the thickest, and the lingual enamel thickness was greater than buccal. Pan and Gorilla present the opposite pattern with enamel being thinnest occlusally. Comparison at each molar position between the maxilla and mandible revealed very few significant differences in fossil hominins but some evidence of significantly thicker maxillary enamel (AET) in modern humans and thinner maxillary enamel in Pan (RET).

釉质厚度仍然是人参系统中的一个重要形态学特征，并且经常被纳入人参物种的饮食结构中。我们通过检查大型上颌上颌骨更新世人类（n = 62）的上颌磨牙样本以及现存非人类猿类（n = 48）和现代人类（n = 29）的对比样本，扩展了下颌磨牙釉质厚度的先前研究。 。通过显微断层摄影术生成2D截面的中间平面，并测量标准的牙齿组织变量以计算平均牙釉质厚度（AET）和相对牙釉质厚度（RET）。还检查了冠的舌，颊和颊区域的AET。这项研究证实了以前的发现，即整个上新世更新时期的牙釉质厚度增加，这是最薄的。南方古猿（Australopithecus anamensis）和博伊古猿（Austrolopithecus boisei）的峰值，早期的人标本，其牙釉质中等。与以前的发现一致，发现牙釉质厚度的2D平面是不良的分类学判别器，人类化石之间没有观察到统计学上的显着差异。对于人类化石，现代人和庞哥来说，牙釉质的咬合区最厚，舌质珐琅质的厚度大于颊颊。潘与大猩猩呈现相反的图案，牙釉质最薄。在上颌骨和下颌骨的每个臼齿位置进行比较后发现，人类化石的化石几乎没有显着差异，但有证据表明现代人的上颌釉质（AET）明显较厚，而Pan（RET）上颌釉质较薄。