Why do humans have such a prominent nose? The final result of phylogenesis: A significant reduction of the splanchocranium on account of the neurocranium

Abstract

During the last few decades several authors tried to clarify the anthropological aspects of the shape of the human nose and why it has so emphasized projection. Our hypothesis suggests the essentiality of the role of morphologic changes of the human skull which occurred during the phylogenesis. It seems that erectile posture of the man caused remarkable morphological changes of the skull base shape thus being a part of morphologic evolution. The changes in the shape of the human spine from birth to adulthood show a philogenesis in short: a newborn has an almost flat spine like quadrupeds (except in the sacro-coccigeal region), but the spine gets increasingly bent as the person grows (lumbar lordosis, thoracic kyphosis, cervical lordosis). It is well known that the sphenoidal angle was less emphasized in prehistoric man than in modern man. In addition, the cervical spine position in the gorilla, Neanderthal man and modern man is quite different in terms of anterior inclination. Accordingly, there is a great degree of maxillary and mandible reduction in humans. The same differences can be seen when comparing the skull shapes of gorilla, gibbons, Neanderthals and modern man. A major reason for the maxillary and mandible reduction in humans is that their way of feeding has changed remarkably with time. In lower primates and other animals, nasal function, particularly olfaction, may be essential for day-to day survival. In humans, however, this is less important although both impaired nasal breathing and olfaction may affect the function in the other body organs and, of course, influence the quality of life. Nasal configuration in recent humans seems to be associated with the internal nasal cavity wideness and nasal bridge elevation which just happened because of newly developed physiological needs. The skull base angulation leads directly to obvious changes in splanchocranium on the account of neurocranium, since previous is getting "squeezed", by angulation of the surrounding bones, and the other one gets more room for the further development according to human's intellectual needs. The final morphologic result of the squeezing of the splanchocranium, in fact a side-effect of these phylogenetic changes, is a protrusion of its most anterior parts more anteriorly, that is a prominent nose in humans which is a hallmark of the modern man.