Department of Health Sciences, East Tennessee State University, Johnson City, TN 37614, USA.
Research Group Computed Tomography, University of Applied Sciences Upper Austria, 4600 Wels, Austria.
Proc Biol Sci. 2022 Jun 8;289(1976):20220711. doi: 10.1098/rspb.2022.0711. Epub 2022 Jun 15.
Australopiths, a group of hominins from the Plio-Pleistocene of Africa, are characterized by derived traits in their crania hypothesized to strengthen the facial skeleton against feeding loads and increase the efficiency of bite force production. The crania of robust australopiths are further thought to be stronger and more efficient than those of gracile australopiths. Results of prior mechanical analyses have been broadly consistent with this hypothesis, but here we show that the predictions of the hypothesis with respect to mechanical strength are not met: some gracile australopith crania are as strong as that of a robust australopith, and the strength of gracile australopith crania overlaps substantially with that of chimpanzee crania. We hypothesize that the evolution of cranial traits that increased the efficiency of bite force production in australopiths may have simultaneously weakened the face, leading to the compensatory evolution of additional traits that reinforced the facial skeleton. The evolution of facial form in early hominins can therefore be thought of as an interplay between the need to increase the efficiency of bite force production and the need to maintain the structural integrity of the face.
南方古猿，一种生活在非洲上新世至更新世的人科动物，其颅骨具有衍生特征，据推测，这些特征增强了面部骨骼以应对摄食负荷，并提高了咬合力的产生效率。强壮的南方古猿的颅骨被认为比纤细型南方古猿的颅骨更强壮、更高效。先前力学分析的结果大体上与这一假设一致，但这里我们表明，该假设在机械强度方面的预测并未得到满足：一些纤细型南方古猿的颅骨与强壮型南方古猿的颅骨一样强壮，而且纤细型南方古猿颅骨的强度与黑猩猩颅骨的强度有很大的重叠。我们假设，在南方古猿中增加咬合力产生效率的颅骨特征的进化可能同时削弱了面部，导致额外的强化面部骨骼的特征进行了补偿性进化。因此，早期人类面部形态的进化可以被认为是增加咬合力产生效率的需要和保持面部结构完整性的需要之间的相互作用。
