Bipedalism and dental occlusion
The new research rejects the common belief that features of our teeth and mandibles would have been a direct consequence of changes in diet; these changes, it is claimed, would have occurred because of feeding adaptations to new environments outside the tropical woodlands, then the appearance of the first Paleolithic tools, and the use of fire for cooking food. Conversely, comparing evolutionary rates of changes in the shape of mandibles across a large morphometric dataset dealing with extinct and living primates, the researchers have observed that the jaws of our species and its closest evolutionary relatives, such as the Australopithecine or the Neanderthals, changed over the last millions years more rapidly than in any other primate group.
According to this study, the explanation of such a surprising evolutionary acceleration has to be found in the new structural relationships between the mandible, the neck and the skull, due to the acquisition of our unique pattern of locomotion and posture, which took place between 6 and 7 million years ago. This indicates that two key-processes of human evolution, i.e. bipedalism and dental occlusion, are much more interconnected than previously believed.
Thus, the new structural arrangements produced cascading effects, which allowed to the first bipedal hominids to adapt to the consumption of more tough foods (seeds and tubers) in scattered forest environments and in the savannahs. Subsequently, such changes would have allowed the first representatives of the genus Homo to change their diet, with increasing consumption of meat and cooked foods, up to the gracile jaws of Homo sapiens, with our small teeth and the emergence of our curious chin.
Unexpectedly rapid evolution of mandibular shape in hominins - P. Raia, M. Boggioni, F. Carotenuto, S. Castiglione, M. Di Febbraro, F. Di Vincenzo, M. Melchionna, A. Mondanaro, A. Papini, A. Profico, C. Serio, A. Veneziano, V.A. Vero, L. Rook, C. Meloro, G. Manzi - Scientific Reports, 2018; 8: 7340. DOI: 10.1038/s41598-018-25309-8
Giorgio Manzi, Department of Environmental Biology, Sapienza University of Rome