Brow ridge: Difference between revisions

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This page is racist. It's not good enough to use one ethnic group to discuss a bias. You need more than one ethnic group.

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+This page is racist. It's not good enough to use one ethnic group to discuss a bias. You need more than one ethnic group.
-[[File:Workii tribe of Gilbert River Australoid.png|thumb|200px|[[Australian Aborigine]] man of the [[Workii people]]]]
-[[File:Workii tribe woman of Gilbert River Australoid.png|thumb|200px|[[Australian Aborigine]] woman of the [[Workii people]]]]
-The '''supraorbital ridge''' (or '''brow ridge''') refers to a bony ridge located above the eye sockets of all [[primate]]s. In ''[[Homo sapiens sapiens]]'' (modern humans) the eyebrows are located on their lower margin.
-Other terms in use are:
-* ''supraorbital arch''
-* ''frontal torus''
-* ''supraorbital torus''
-* ''superciliary ridge''
-* ''arcus superciliaris'' (Latin, meaning "superciliary arch")
-* ''supraorbital margin'' and ''the margin of the orbit''
-==Anthropological concept==
-[[Image:Gorilla Cin Zoo 020.jpg|thumb|Gorilla face.]]
-[[Image:Young male chimp.png|thumb|Chimpanzee face.]]
-The size of these ridges varies also between different species of primates, either living or fossil. The closest living relatives of humans, the [[great apes]], have a relatively pronounced supraorbital ridge, which has also been called a ''frontal torus''<ref name= sollas>{{Cite journal|last= [[William Johnson Sollas|Sollas, W.J.]] |title= The Taungs Skull. |journal= Nature|volume= 115 |pages= 908–9 }}</ref> while in modern humans it is relatively reduced. The fossil record indicates that the supraorbital ridge in early hominins was reduced as the cranial vault grew and became positioned vertically, above the face.
-Some [[Paleoanthropology|paleoanthropologists]] distinguish between ''torus'' and ''ridge.'' In anatomy, a ''[[Torus (disambiguation)|torus]]'' is a projecting shelf of bone.<ref>For some basic English definitions refer to the [[American Heritage Dictionary]] online under [http://www.bartleby.com/61/92/S0909200.html supraorbital] and [http://www.bartleby.com/61/35/T0283500.html torus]. Webster's Third New International Dictionary also does not make the distinction.</ref> Fossil [[hominid]]s, in this theory, have the ''frontal torus'',<ref name=sollas/> but modern humans only have the ridge.
-==Purpose==
-{{See also|Human skeletal changes due to bipedalism}}
-The brow ridge functions to reinforce the weaker bones of the face in much the same way that the chin of modern humans reinforces their comparatively thin [[Human mandible|mandible]]s. This was necessary in [[pongid]]s and early hominids because of the tremendous strain put on the [[Human cranium|cranium]] by their powerful chewing apparatuses, which is best demonstrated by any of the members of the genus ''[[Paranthropus]]''. The brow ridge was one of the last traits to be lost in the path to modern humans, and only disappeared with the development of the modern pronounced [[frontal lobe]]. This is one of the most salient differences between ''Homo sapiens'' and ''[[Neanderthal|Homo neanderthalensis]]''.
-[[Image:Europaeid types.jpg|thumb|200px|''Meyers Blitz-Lexikon'' ([[Weimar Republic|Leipzig, 1932]]) shows "Caucasoid types".  Caucasoids have the second largest brow ridge under Australoids.<!--pg 84-->.<ref name=Wilkenson />]]
-[[Image:NSRW Australian Types.png|thumb|right|Some faces of non-European Australians ca. 1914. Australoids have the largest browridges.<!--pg87-->.<ref name=Wilkenson />]]
-==In modern humans==
-Forensic anthropologist Caroline Wilkenson said that Australoids have the largest brow ridges "''with moderate to large supraorbital arches''",<!--pg87--><ref name=Wilkenson />  Caucasoids have the second largest brow ridges with "''moderate supraorbital ridges''",<!--pg 84--><ref name=Wilkenson />  Negroids have the third largest brow ridges with an "''undulating supraorbital ridge''"<ref name=Wilkenson /> and Mongoloids are "''absent browridges''"<!--pg86-->.<ref name=Wilkenson>Wilkenson, Caroline. Forensic Facial Reconstruction. Cambridge University Press. 2004. ISBN 0521820030{{Page needed|date=September 2010}}</ref> Anthropologist [[Ashley Montagu]] said Mongoloids are "''absent browridges''" and he said "''such ridges are absent in the skulls of both sexes in Mongoloid peoples.''"<ref>Montagu, A. (1989). Growing Young. Bergin & Garvey: CT.</ref> Dr. Marta Mirazon Lahr of the Department of Biological Anthropology at [[Cambridge University]] said the "[[Paleoindian]]" has "[[Mongoloid race#Proto-Mongoloids|proto-Mongoloid]]" "morphology" such as "pronounced development of supraorbital ridges"<ref>Lahr, M. M. (1995), Patterns of modern human diversification: Implications for Amerindian origins. American Journal of Physical Anthropology, 38: 163–198. {{doi|10.1002/ajpa.1330380609}}</ref> Anthropologist [[Arnold Henry Savage Landor]] described the [[Ainu people|Ainu]] as having deep-set eyes and a large and prominent browridge.<ref>Arnold Henry Savage Landor (1970). Alone with the hairy Ainu: or, 3.800 miles on a pack saddle in Yezo and a cruise to the Kurile islands</ref>
-==Spatial model==
-Much of the groundwork for the spatial model was laid down by Schultz (1940). He was the first to document that at later [[Child development stages|stages of development]] (after age 4) the growth of the orbit would outpace that of the eye. Consequently, he proposed that facial size is the most influential factor in orbital development, with orbital growth being only secondarily affected by size and ocular position.
-Weindenreich (1941) and Biegert (1957, 1963) argued that the supraorbital region can best be understood as a product of the orientation of its two components, the face and the neurocranium.
-The most composed articulation of the spatial model was presented by Moss and Young (1960), who stated that "the presence… of supraorbital ridges is only the reflection of the spatial relationship between two functionally unrelated cephalic components, the orbit and the brain" (Moss and Young, 1960, p282). They proposed (as first articulated by Biegert in1957) that during infancy the neurocranium extensively overlaps the orbit, a condition that prohibits [[Supraorbital foramen|brow ridge]] development. As the splanchocranium grows, however, the orbits begin to advance, thus causing the anterior displacement of the face relative to the brain. Brow ridges then form as a result of this separation.
-To put it simply, the Spatial model proposes that supraorbital torus development can be best explained in terms of the disparity between the anterior position of the orbital component relative the neurocranium.
-==Bio-mechanical model==
-Research done on this model has largely been based on earlier work of Endo (1965, 1966, 1970, and 1973). By applying pressure similar to the type associated with [[chewing]], he carried out an analysis of the structural function of the supraorbital region on dry human and gorilla [[skull]]s. His findings indicated that the face acts as a pillar that carries and disperses tension caused by the forces produced during mastication. Russell (1982, 1985) and Oyen et al. (1979a) elaborated on this idea, suggesting that amplified facial projection necessitates the application of enhanced force to the anterior dentition in order to generate the same bite power that individuals with a dorsal deflection of the facial skull exert. In more prognathic individuals, this increased pressure triggers bone deposition to reinforce the brow ridges, until equilibrium is reached.
-In their 1979(a) publication, Oyen et al. conducted a cross-section study of ''[[Papio anubis]]'' in order to ascertain the relationship between palate length, incisor load and Masseter lever efficiency, relative to torus enlargement. Indications found of osteoblastic deposition in the glabella region were used as evidence for supraorbital enlargement. Oyen et al.’s data suggested that more prognathic individuals experienced a decrease in load/lever efficiency. This transmits tension via the frontal process of the maxilla to the supraorbital region, resulting in a contemporary reinforcement of this structure. This was also correlated to periods of tooth eruption.
-In a later series of papers, Russell (1985, 1986a, and 1986b) developed aspects of this mode further. Employing an adult Australian sample, she tested the association between brow ridge formation and anterior dental loading, via the craniofacial angle (prosthion-nasion-metopion), maxilla breadth, and discontinuities in food preparation such as those observed between different age groups. Finding strong support for the first two criteria, she concluded that the supraorbital complex is formed as a result of increased tension due to the widening of the maxilla, thought to be positively correlated with the size of the messeter muscle, as well as with the improper orientation of bone in the superior orbital region.
-In short, the bio-mechanical model predicts that morphological variation in torus size is the direct product of differential tension caused by mastication, as indicated by an increase in load/lever ratio and broad craniofacial angle (Oyen and Russell, 1984, p.&nbsp;368-369).
-==See also==
-* [[Occipitofrontalis muscle]]
-* [[Supraorbital foramen]]
-==References==
-{{Refimprove|date=September 2008}}
-{{Reflist}}
-==Further reading==
-*{{Cite journal|last1=Endo |first1=B |year=1965 |title=Distribution of stress and strain produced in the human face by masticatory forces |journal=Journal of the Anthropological Society of Nippon |volume=73 |pages=123–36|doi=10.1537/ase1911.73.123|issue=4}}
-*{{Cite journal|last1=Endo |first1=B |year=1970 |title=Analysis of stresses around the orbit due to masseter and temporalis muscles respectively |journal=Journal of the Anthropological Society of Nippon |volume=78 |pages=251–66|doi=10.1537/ase1911.78.251|issue=4}}
-*{{Cite journal|last1=Endo |first1=B |year=1973 |title=Stress analysis of the gorilla face |journal=Primates |volume=14 |pages=37–45}}
-*{{Cite journal|first1=Mary Doria |last1=Russell |month=June |year=1985 |title=The Supraorbital Torus: 'A Most Remarkable Peculiarity' |journal=Current Anthropology |volume=26 |issue=3 |pages=337–360  |doi=10.1086/203279}}
-*{{Cite journal|last1=Oyen |first1=Ordean J. |last2=Rice |first2=Robert W. |last3=Cannon |first3=M. Samuel |month=July |year=1970 |title=Browridge structure and function in extant primates and Neanderthals |journal=American Journal of Physical Anthropology |volume=51 |issue=1 |pages=83–95 |doi=10.1002/ajpa.1330510111}}
-==External links==
-*[http://www.csuchico.edu/anth/Module/frontal.html The Frontal Bone], California State University at Chico site.
-*[http://www.websters-online-dictionary.org/ar/arcus+superciliaris.html ARCUS SUPERCILIARIS], Webster's Online Dictionary.
-{{DEFAULTSORT:Supraorbital Ridge}}
-[[Category:Primate anatomy]]
-[[Category:Bones of the head and neck]]
-[[Category:Facial features]]
-[[br:Gwareg-abrant]]
-[[ca:Arc superciliar]]
-[[cs:Nadočnicový oblouk]]
-[[de:Überaugenwulst]]
-[[fr:Arcade sourcilière]]
-[[ja:眼窩上隆起]]
-[[pl:Łuk brwiowy]]