PubMed1997
Comparative phylogenic movements of skull points can be obtained using vestibular orientation and skulls from various mammals after reducing the bimediocondyle distance to approximately 100 mm (as in man). With this method, the condyle is seen to move backwardly and rise in a very thin bony area which will be covered by the increasing volume of the encephalus. A "mandibulocerebral" index of less than 100 is a criteria of humanoid species. A part posterior to the fixed zone in primate which will become the temporal condyl in man is eroded by the mandibular condyle. The tympanum migrates upwardly and posteriorly in primates and turns forwardly in man, contributing to limit the glenoid cavity posteriorly. The anterior limit to mandibular propulsion in primates is the intercanine bite; this disappears in man as does the post-glenoid apophysis which is reduced to a tubercle with no limiting effect. In man, function of the temporomandibular joint depends on its more delicate construction than in primates. The major humanoidizing processes alone, i.e. posterior movement of the jaws and their reduced volume, bipedism, and amplification of the cerebral volume, are sufficient to explain this situation which results from the effect of phylogenic evolution.