Paleoanthropology Group, Department of Paleobiology, Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain.
Departamento de Ingeniería Térmica y Fluidos, Universidad de Cartagena, Cartagena, Spain.
Anat Rec (Hoboken). 2022 Aug;305(8):1962-1973. doi: 10.1002/ar.24790. Epub 2021 Oct 12.
The facial differences between recent Pan troglodytes and Homo sapiens can be used as a proxy for the reduction of facial prognathism that happened during evolutionary transition between Australopithecines and early Homo. The projecting nasal morphology of Homo has been considered both a passive consequence of anatomical reorganization related to brain and integrated craniofacial evolution as well as an adaptation related to air-conditioning during physiological and behavioral shifts in human evolution. Yet, previous research suggested impaired air-conditioning in Homo challenging respiratory adaptations based on computational fluid dynamics (CFD) and airflow simulations. Here we improved CFD model at the inflow region and also carried out three-dimensional (3D) geometric morphometrics to address the hypothesis of impaired air-conditioning in humans and species differences in airway shape. With the new CFD model we simulated pressure, velocity, and temperature changes in airflow of six adult humans and six chimpanzees and analyzed 164 semi-landmarks of 10 humans and 10 chimpanzees for 3D size and shape comparisons. Our finding shows significantly different internal 3D nasal airways. Also, species means of pressure, velocity, and temperature differed statistically significantly. However, form-related differences in temperature exchanges seem subtle and may question adaptive disadvantages. We rather support a hypothesis of craniofacial changes in the Australopithecus-Homo transition that are related to brain evolution and craniofacial integration with facial and nasal modifications that contribute to maintain respiratory adaptations related to air conditioning.
近期的南方古猿与智人之间的面部差异可以作为南方古猿和早期人类进化过程中面部前突减少的替代指标。人类突出的鼻腔形态被认为既是与大脑相关的解剖结构重组以及综合颅面进化的被动结果，也是人类进化过程中生理和行为转变时与空气调节相关的适应结果。然而，之前的研究基于计算流体动力学（CFD）和气流模拟，表明人类的空气调节能力受损，从而对呼吸适应提出了挑战。在这里，我们改进了流入区域的 CFD 模型，并进行了三维（3D）几何形态测量，以解决人类空气调节受损和气道形状物种差异的假设。利用新的 CFD 模型，我们模拟了六个成年人和六个黑猩猩的气流中的压力、速度和温度变化，并分析了 10 个人类和 10 个黑猩猩的 164 个半标志点，以进行 3D 大小和形状比较。我们的研究结果表明，内部的 3D 鼻腔气道存在显著差异。此外，物种的压力、速度和温度平均值在统计学上存在显著差异。然而，与形态相关的温度交换差异似乎很小，可能会对适应劣势提出质疑。我们更支持一个假说，即南方古猿-人类进化过程中的颅面变化与大脑进化以及颅面整合有关，与面部和鼻腔的修饰一起，有助于维持与空气调节相关的呼吸适应。
