When this does not occur, particularly during infantile development, the palate curves (ogival palate) and the occlusion is altered (anterior open bite and posterior crossbite). The tongue must be perfectly positioned in relation to the palate for the palate and dental arches to develop correctly. They form part of the environmental factors capable of modifying these structures ( Shanhraki et al., 2012). The pharynx in adult humans is much longer than in children and the hyoid bone and larynx descend ( Lieberman et al., 2001), eliminating the closure between the epiglottis and the soft palate.Ĭompared to a lactating human or a chimpanzee, the descended pharynx of an adult has the acoustic significance of producing sounds ( Lieberman et al., 2001) as the vocal tract includes the pharyngeal, oral and nasal cavities.Īnomalous oral habits prolonged over time have altered craniofacial development and growth. After the chimpanzee’s birth, the larynx descends as occurs in children, but the hyoid bone does not ( Nishimura et al., 2006). This is similar to what occurs in a lactating human. The chimpanzee’s epiglottis covers the ventral side of the oropharynx, overlapping and extending over and behind the free edge of the soft palate. The upright position allowed mandibular horizontalization, lengthening of the pharynx and descent of the larynx. The relation between the larynx, pharynx, and oral cavity changed. In addition to language three conditioning factors could have influenced the development and evolution of the hard structures relating to the oral cavity of modern man: bipedalism, oral habits, and genetics.īipedalism resulted in a series of adaptive phenomena that would later contribute to the appearance of the spoken language. The working hypothesis of this study is that the bone structures that participate in phonatory function have evolved conditioned among other factors to the specific movements of spoken language, and with the purpose of facilitating such movements.īy studying the bone structures of the temporomandibular joints (mandibular condyle and articular tubercle of the temporal bone), the bone structures surrounding the tongue (alveolar process, mandible, and hard palate) and the hard structures related to the lower lip (chin and its inclinations), it may be possible to establish associations with speech. human facial bones.Īlthough the difference in body mass between humans and chimpanzees is always in favor of humans, the maxillofacial massif appears larger and more prominent in chimpanzees. The present study involves a comparative anatomical investigation of chimpanzee facial bones vs. Mammals have had a larynx, pharynx, and oral cavity for many millions of years and these structures allow the different species to communicate. In effect, speech is a characteristic exclusive to Homo sapiens, though the human phonatory apparatus is not a specific organ. “Of all animals, only Man possesses speech” (Aristotle). This leads to the conclusion that, at least in part, speech is behind all these changes, although it is difficult to establish a cause-effect relationship. There is a greater lingual space and there is also a chin that suggests a muscular stimulant. The human skull has temporomandibular joints that are comparatively less flat with a more limited movement. ![]() The refinement of the supralaryngeal vocal tract in the human species must have co-evolved with speech fairly recently. ![]() However, the majority of the variables studied in skulls and mandibles are greater in chimpanzees, which suggests that the evolution of the oral zone in humans has suffered a reduction in size with changes in shape. ![]() On average, humans weigh 70 kg and chimpanzees 44 kg. The number of mandibular movements involved in speech is far greater than those used in chewing, which must have conditioned the evolution of the oral structures implicated in the development of language. Together with other factors (bipedalism, habits, and genetics) speech in humans must have played an important role in the aforementioned differences between humans and chimpanzees. This has been confirmed with the analysis of new variables. It is obvious that there are differences between humans and chimpanzees in the bone morphology of the oral cavity structures.
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