Impaired Air Conditioning within the Nasal Cavity in Flat-Faced Homo

• DOI: 10.1371/journal.pcbi.1004807
• Publication Date: 2016-03-24T17:53:43Z
• Authors: Takeshi Nishimura; Futoshi Mori; Sho Hanida; Kiyoshi Kumahata; Shigeru Ishikawa; Kaouthar Samarat; Takako Miyabe-Nis...; Misato Hayashi; Masaki Tomonaga; Juri Suzuki; Tetsuro Matsuzawa; Teruo Matsuzawa
• Keywords: 0301 basic medicine; Pan troglodytes; QH301-705.5; Air; Temperature; Hominidae; Humidity; 03 medical and health sciences; Inhalation; Species Specificity; Animals; Humans; Macaca; Air Conditioning; Biology (General); Nasal Cavity; Rheology; Research Article

We are flat-faced hominins with an external nose that protrudes from the face. This feature was derived in genus Homo, along facial flattening and reorientation to form a high nasal cavity. The passage conditions inhaled air terms of temperature humidity match required lung, its anatomical variation is believed be evolutionarily sensitive ambient atmospheric given habitat. In this study, we used computational fluid dynamics (CFD) three-dimensional topology models under same simulation conditions, investigate air-conditioning performance humans, chimpanzees, macaques. CFD showed horizontal straight flow chimpanzees macaques, contrasting upward curved humans. conditioned poorly humans compared nonhuman primates. Virtual modifications human topology, which vestibule valve modified resemble those change airflow horizontal, but have little influence on These findings suggest morphological only weakly atmosphere conditions; rather, cavity formed simply by evolutionary reorganization divergence Homo other hominin lineages, impairing performance. Even though not adjusted well within it can fully subsequently pharyngeal cavity, lengthened Homo. Thus, faculty passages probably impaired early members, although they survived successfully fluctuating climate Plio-Pleistocene, then moved "Out Africa" explore more severe climates Eurasia.