Homo sapiens, Chimpanzees and the Enigma of Language.

OBJECTIVES: The present study explores the hypothesis that the anatomical bone structures of the oral cavity have probably evolved under the influence of language function. The possible changes have been evaluated by comparing two close species essentially differentiated from each other by spoken language. MATERIALS AND METHODS: Twenty dry skulls and 20 mandibles of modern Caucasians were compared with 12 dry skulls and 12 mandibles of chimpanzees, with the analysis of 37 variables and the definition of new anatomical parameters. RESULTS: A number of highly significant differences were found between humans and chimpanzees. The human temporomandibular joint is comparatively less flat and has a more limited excursive movement range, with structural elements that seem to be lighter. A significant difference is noted in mandibular alveolar vergency and in the internal slope of the mandibular symphysis where the oral cavity's morphology is modified, thereby increasing the free space for tongue movements in humans. The chin, which is unique to the human species, is quantified through the external slope of the mandibular symphysis with a lesser angle in humans. DISCUSSION: It is obvious that there are differences between humans and chimpanzees in the bone morphology of the oral cavity structures. This has been confirmed with the analysis of new variables. 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. 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. On average, humans weigh 70 kg and chimpanzees 44 kg. 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. The refinement of the supralaryngeal vocal tract in the human species must have co-evolved with speech fairly recently. The human skull has temporomandibular joints that are comparatively less flat with a more limited movement. There is a greater lingual space and there is also a chin that suggests a muscular stimulant. 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.

Morphometric analysis of the dorsum linguae in patientswith Oral Lichen Planus

Objective: Morphometric study of the dorsum linguae in patients with Oral Lichen Planus (OLP).Material and Method: In 236 patients with a clinicopathologic diagnosis of OLP, 111 were found to have involvementof the dorsum linguae. For the purposes of the study, 41 of these cases were used, due to the availabilityof photographic records fulfilling quality conditions according to objective criteria. The experimental variablewas defined as the proportion of affected dorsum linguae measured and calculated using the MIP4(R) computersoftware.Results: In 236 patients with OLP, the mucosa of the dorsum linguae was affected in 47.6% of the cases (total111). The proportion of affected area was studied in 41 of these cases, 8 men (19.5%) and 33 women (80.5%). In73% of these cases, the affected area was less than 50% of the total surface of the dorsum linguae. There wereno statistically significant differences (p=0.495) in relation to age and proportion of lingual surface affected. Onthe other hand, significant statistical differences were found between the period of disease evolution and area oflingual involvement (p=0.044).Conclusion: Lingual involvement is frequent in patients with OLP, and manifests as de-papillate areas to the leftand right of the median sulcus of tongue (occasionally linked by an isthmus) and having a certain "butterfly wing" symmetry (AU)

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Morphometric analysis of the dorsum linguae in patients with Oral Lichen Planus.

OBJECTIVE: Morphometric study of the dorsum linguae in patients with Oral Lichen Planus (OLP). MATERIAL AND METHOD: In 236 patients with a clinicopathologic diagnosis of OLP, 111 were found to have involvement of the dorsum linguae. For the purposes of the study, 41 of these cases were used, due to the availability of photographic records fulfilling quality conditions according to objective criteria. The experimental variable was defined as the proportion of affected dorsum linguae measured and calculated using the MIP4(R) computer software. RESULTS: In 236 patients with OLP, the mucosa of the dorsum linguae was affected in 47.6% of the cases (total 111). The proportion of affected area was studied in 41 of these cases, 8 men (19.5%) and 33 women (80.5%). In 73% of these cases, the affected area was less than 50% of the total surface of the dorsum linguae. There were no statistically significant differences (p=0.495) in relation to age and proportion of lingual surface affected. On the other hand, significant statistical differences were found between the period of disease evolution and area of lingual involvement (p=0.044). CONCLUSION: Lingual involvement is frequent in patients with OLP, and manifests as de-papillate areas to the left and right of the median sulcus of tongue (occasionally linked by an isthmus) and having a certain " butterfly wing" symmetry.

A study of the movements of the human temporomandibular joint complex in the cadaver.

The objective of this study was to define the movements in the sagittal plane of the articular disk relative to the temporal bone and the mandibular condyle respectively, on jaw-opening in the absence of loads. Four temporomandibular joints from two human cadavers were used as materials in the study. Ten steel needles were placed in the lateral plane. Lateral photographs were taken of the articular area in different mandibular positions. OXY reference systems were adapted to the temporal and condylar points. The movements of the disk relative to the temporal bone are statistically different from those relative to the condyle. These findings are consistent with the new concept that the mandible joins the skull through two Temporomandibular Joint Complexes (TMJCs), one on each side and each one made up of a reciprocally fitting temporodiskal joint and a disko-condyle of the condylar type.