Homo sapiens, Chimpanzees and the Enigma of Language

ObjectivesThe 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 MethodsTwenty 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.ResultsA 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.DiscussionIt 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

Hypothesis about the appearance of the vermillion border of the lips in Homo sapiens

The vermillion border of the lips is an exclusive aspect of Homo sapiens, and is one of the few morphological elements that mark the facial difference with the rest of hominids. On the other hand, modern spoken language is also a characteristic of the human species. Spoken language and the vermillion border could have a relationship. Hypothesis: About 200,000 years ago, spoken language appeared in Africa. The friction between the lips when pronouncing bilabial syllables could have been the origin of the disappearance of hair follicles, resulting in the emergence of the vermillion border of the lips. This study tries to evaluate the influence of persistent, non-aggressive friction on the density of the hair follicles in a given area of human skin. Material and methods: Twenty-five men between the ages of 25 and 95 years old, who had worn a gold ring on the finger of one hand for more than 5 years, were selected. A trichogram of the skin of the finger with the ring was made and compared with the skin of the finger without a ring on the opposite hand. The data analysis was carried out with the SPSS version 18 statistical package and the Kolmogorov-Smirnov, Student T, Mann Witney's U and Spearman tests were used. Results: The area of the collective study of fingers with a ring gave an average number of hair follicles of 7.0 with a standard deviation of 2.80. The area of the collective control fingers without a ring gave an average number of hair follicles of 9.76 with a standard deviation of 4.53. The differences between both groups are statistically very significant with p-value of 0.002. Discussion: The results obtained prove that there is a direct influence of persistent, non-aggressive friction on the hair density of human skin on the finger. It was verified that there is a 28.3% decrease in the average values of the follicles, which can be considered to be an important effect. Conclusions: It can be concluded that the hypothesis initially proposed to explain the appearance of the vermillion border in Homo sapiens is plausible. Also that the friction between lips, caused by the spoken language, especially its bilabial syllables, can be the origin, as in the case of a ring rubbing against the skin of a finger over several years