Teeth of omnivores face a formidable evolutionary challenge: how to protect against fracture and abrasive wear caused by the wide variety of foods they process. It is hypothesized that this challenge is met in part by adaptations in enamel microstructure. The low-crowned teeth of humans and some other omnivorous mammals exhibit multiple fissures running longitudinally along the outer enamel walls, yet remain intact. It is proposed that inter-prism weakness and enamel property gradation act together to avert entry of these fissures into vulnerable inner tooth regions and, at the same time, confer wear resistance at the occlusal surface. A simple indentation experiment is employed to quantify crack paths and energetics in human enamel, and an extended-finite-element model to evaluate longitudinal crack growth histories. Consideration is given as to how tooth microstructure may have played a vital role in human evolution, and, by extension, to other omnivorous mammals.

杂食动物的牙齿面临着巨大的进化挑战：如何防止它们加工的各种食物引起的断裂和磨损。据推测，这一挑战部分是通过釉质微观结构的适应来解决的。人类和其他一些杂食性哺乳动物的低牙冠牙齿呈现出沿外釉质壁纵向延伸的多个裂缝，但仍保持完整。建议棱镜间弱点和牙釉质属性渐变共同作用以防止这些裂缝进入脆弱的内牙区域，同时赋予咬合面耐磨性。一个简单的压痕实验被用来量化人体牙釉质中的裂纹路径和能量，以及一个扩展的有限元模型来评估纵向裂纹扩展历史。