Institute of Human Origins, Arizona State University, Tempe, AZ, USA.
School of Human Evolution and Social Change, Arizona State University, Tempe, AZ, USA.
Biol Lett. 2020 Jan;16(1):20190671. doi: 10.1098/rsbl.2019.0671. Epub 2020 Jan 22.
As the tissue most directly responsible for breaking down food in the oral cavity, the form and function of enamel is obviously of evolutionary significance in humans, non-human primates and other vertebrates. Accordingly, a standard metric, relative enamel thickness (RET), has been used for many decades to provide insights into vertebrate and human palaeobiology. Relatively thick enamel has evolved many times in vertebrates including hominoids (the group to which living humans and fossil hominins belong), and this pattern is thought to provide information about taxonomy, phylogeny, functional anatomy and diet. In particular, relatively thick enamel is thought to make tooth crowns strong so that they resist fractures associated with eating mechanically resistant foods. Here, we use current models of tooth biomechanics to show that RET is at best only moderately informative of function and diet in living hominoids and fossil hominins, and at worst provides misleading information. We propose a new metric, absolute crown strength, to assess the resistance of teeth to fracture, and identify what may be a novel characteristic of tooth strength in fossil hominins.
作为口腔中负责分解食物的最重要组织，牙釉质的形态和功能在人类、非人类灵长类动物和其他脊椎动物中显然具有进化意义。因此，相对牙釉质厚度（RET）作为一种标准衡量指标，已经被使用了数十年，以提供有关脊椎动物和人类古生物学的深入了解。相对较厚的牙釉质在脊椎动物中多次进化，包括人科动物（包括现存人类和已灭绝的人科动物），这种模式被认为提供了关于分类学、系统发育、功能解剖和饮食的信息。特别是，相对较厚的牙釉质使牙冠更强壮，从而抵抗与食用机械抗性食物相关的断裂。在这里，我们使用当前的牙齿生物力学模型来表明，RET 最多只能适度反映现生人科动物和已灭绝人科动物的功能和饮食，而在最坏的情况下，它提供了误导性的信息。我们提出了一种新的衡量标准，即绝对冠部强度，来评估牙齿对断裂的抵抗力，并确定在已灭绝的人科动物的牙齿强度中可能存在的一个新特征。
