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Facial Angle

size human line brain

In the eighteenth century, the increasing involvement of European nations with colonies in the tropics brought Europeans into contact not only with tropical human populations but also with tropical nonhuman animals. A major attempt to classify the creatures of the world on the basis of assumed relationships was one of the consequences of this expanded European consciousness, and the major system of classification drawn up by the Swedish naturalist Carolus Linnaeus (1707–1778) was one of the results. His Systema Naturae was first published in 1735, with a definitive tenth edition appearing in 1758. Linnaeus assigned human beings, whom he defined in binomial fashion as Homo sapiens , to the order he called “Primates,”which also includes monkeys and apes.

Later in the eighteenth century, the Dutch anatomist Petrus Camper (1722–1789), suggested a quantitative way to assess the relationships of some of the members of the order Primates. Camper developed his method in 1760 and presented it for public discussion in 1770, but it was not formally published until 1791, two years after his death. Camper took as his horizontal orientation a line on the face drawn from the ear opening to the base of the nose. Then, to generate his “facial line,”he drew a line from the forehead to the junction between the upper and the lower lips. The angle made by the horizontal line with the facial line was his “facial angle.”As he viewed it, the normal human condition was represented by facial angles between 70 and 80 degrees. Everything above 80 degrees he declared belonged to the realm of art, and everything below 70 degrees belonged to the animal kingdom.

With monkeys and apes included in the same zoological order as humans, Camper constructed a diagram displaying the facial angle of a monkey, an ape, and a number of human examples. The monkey has not been identified as to species, but the ape is a young orangutan. The orangutans, of course, were native to those parts of Indonesia and Borneo under Dutch control, so a Dutch anatomist would have had access to such specimens. The orang he depicted was a very immature individual, prior to the eruption of any of its permanent dentition. The first human shown was a young Negro bordering on adolescence, and the next was someone from Central Asia, although a number of observers have noted that the individual depicted is markedly different from other examples from this region. The other individuals are Europeans who display nearly vertical faces, for they lack the forward projecting dentitions that contribute to a reduction in the facial angle.

This points up the problem with the facial angle. The size of the brain case and the size of the teeth are under separate and completely unrelated selective force constraints. A single figure, then, cannot reveal anything of much biological significance concerning these two separate features. An increase in the facial angle can be produced by an increase in brain and skull size while face and tooth size remain constant, or by a decrease in tooth and face size while brain and skull size remain constant. The single figure of the facial angle cannot indicate which of these processes has produced that change in the facial angle. The difference in Camper’s illustration between monkey and ape and human being is almost certainly due solely to a relative increase in brain size, while the difference between recent human groups is almost certainly because of the relative differences in tooth size between populations.

Facial Animation and Affective Human-Computer Interaction - Affective Human-Computer Interaction, Expressing Emotion, Facial Animation in MPEG-4, Conclusions [next] [back] Face Recognition Evaluation and Pilots

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