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Origins of dental crowding and malocclusions: an anthropological perspective.
Rose JC, Roblee RD.
Compend Contin Educ Dent. 2009 Jun;30(5):292-300.
The study of ancient Egyptian skeletons from Amarna, Egypt reveals extensive tooth wear but very little dental crowding, unlike in modern Americans. In the early 20th century, Percy Raymond Begg focused his research on extreme tooth wear coincident with traditional diets to justify teeth removal during orthodontic treatment. Anthropologists studying skeletons that were excavated along the Nile Valley in Egypt and the Sudan have demonstrated reductions in tooth size and changes in the face, including decreased robustness associated with the development of agriculture, but without any increase in the frequency of dental crowding and malocclusion. For thousands of years, facial and dental reduction stayed in step, more or less. These analyses suggest it was not the reduction in tooth wear that increased crowding and malocclusion, but rather the tremendous reduction in the forces of mastication, which produced this extreme tooth wear and the subsequent reduced jaw involvement. Thus, as modern food preparation techniques spread throughout the world during the 19th century, so did dental crowding. This research provides support for the development of orthodontic therapies that increase jaw dimensions rather than the use of tooth removal to relieve crowding.
Posts: 2007 | From: Washington State | Registered: Oct 2006
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quote:Originally posted by Evergreen: Origins of dental crowding and malocclusions: an anthropological perspective.
Rose JC, Roblee RD.
Compend Contin Educ Dent. 2009 Jun;30(5):292-300.
"David Greene studied the teeth of skeletons excavated in the Sudan just south of Egypt along the Nile and documented a long-term trend in dental-size reduction for the 10,000-year period. He suggested this reduction in tooth size was from changes in diet and methods of food processing as agriculture was adopted and refined. Analysis of more samples by numerous researchers has established this general trend in tooth-size reduction that is associated with changes in diet. As the diet has become more refined, the consequent increase in dental decay selected for smaller and less complex teeth has moved distally in relation to the skull, such that the body of the mandible now protrudes forward underneath the alveolar bone producing a chin. Because teeth have become smaller without producing excess room in the jaws, other evolutionary mechanisms must have been at work on the alveolar bone and supporting structures of the maxilla and mandible."Posts: 2007 | From: Washington State | Registered: Oct 2006
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quote:Originally posted by Evergreen: Origins of dental crowding and malocclusions: an anthropological perspective.
Rose JC, Roblee RD.
Compend Contin Educ Dent. 2009 Jun;30(5):292-300.
"While it was common to use cranial measurements to document migrations, ancient Egyptian skulls also were employed to demonstrate that the development of Egyptian civilization was produced by the arrival of a "dynastic race" that had a different skull shape. To contradict this racial approach, Carlson and Van Gerven proposed the masticatory function hypothesis, which maintains that changes in the face and skull between the mesolithic and Christian periods (10,000-year span) in the southern Nile Valley were caused by dietary changes initiated by the adoption of agriculture and changing food processing technology."
"Carlson and Van Gerven argued most of the facial changes were not the result of genetic changes but caused by reduced chewing stress during development....they contend that the switch to modern diets had so reduced chewing stress that the jaws did not develop to a sufficient size to hold all the teeth and thus malocclusion became common."Posts: 2007 | From: Washington State | Registered: Oct 2006
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^Excellent addition to the discussions we'd had about this previously. The author does a much better job at explaining this process via Carlson and Van Gerven than Keita, who simply refers to it as the "Post-Pleistocene dental hypothesis". Early Irish and Turner's dismissal of this as even a partial contributing factor suggests extreme bias. I'd be willing, like Keita to place a lot more emphasis on the changes in subsistence but wouldn't discount that the patterns could have been introduced as well, and simply selected for given the changes already occurring (but still reflecting minimal gene flow). Hence, Turner's hasty conclusion that these changes occur too fast to be accounted for by micro-evolution and diet, are naive as this can be interpreted in a number of ways, with the above scenario (posted by you) seemingly being the most plausible.
Posts: 4021 | From: Bay Area, CA | Registered: Mar 2007
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quote:Originally posted by Evergreen: Origins of dental crowding and malocclusions: an anthropological perspective.
Rose JC, Roblee RD.
Compend Contin Educ Dent. 2009 Jun;30(5):292-300.
"Into this fray stepped Robert Corruccini .....who marshaled 20 years of research on cross- cultural differences in occlusal anomalies to support the masticatory functional explanation of malocclusion."
"Corruccini and his colleagues favored the explanation that reduced chewing stress in childhood produced jaws that were too small for the teeth despite the ubiqutious trend in dental size reduction."
"Corruccini also documented a clear association of alveolar bone growth with the functional stimulation of chewing forces that includes measurements of bite-force variation between generations of Eskimos and experimental studies showing changes in mandibular growth of rats and primates between groups consuming hard and soft diets. For example, Lieberman et al raised hyraxes on either cooked or raw foods and showed an approximate 10% difference in facial growth. They not only supported the idea that diet-asscoiated reduction in chewing stress resulted in decreased growth of the mandibular and maxillary arches, but also that animal studies, in general, show both facial reduction and increased malocclusion in the low-force groups."Posts: 2007 | From: Washington State | Registered: Oct 2006
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quote:Originally posted by Sundjata: I'd be willing, like Keita to place a lot more emphasis on the changes in subsistence but wouldn't discount that the patterns could have been introduced as well, and simply selected for given the changes already occurring (but still reflecting minimal gene flow).
Evergreen Writes: Agreed. The Saharo-tropical cranio-facial changes we see from the mid-Holocene Nile Valley may reflect multiple explanations, including:
1) A general trend in cranio-facial reduction from the more typical "West African" modal type we see in the mesolithic period.
2) An introduction of a morphological pattern selected for.
3) The general trend of an elongated morphology due to ecological changes in a hyper-arid sahara.
4) The introduction of an elongated morphological trend from the Red Sea Hills area as Horn of Africa groups back-migrated into the Upper Nile.
Posts: 2007 | From: Washington State | Registered: Oct 2006
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posted
^ Yes excellent work Evergreen, in showing the the factors of evolution at play when it comes to dental-cranial morphology. This is another blow to racialist claims including the use of 'dental patterns' to disprove black identity and/or prove "caucasian" presence.
Posts: 26255 | From: Atlanta, Georgia, USA | Registered: Feb 2005
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quote:Originally posted by Evergreen: 1) A general trend in cranio-facial reduction from the more typical "West African" modal type we see in the mesolithic period.
2) An introduction of a morphological pattern selected for.
3) The general trend of an elongated morphology due to ecological changes in a hyper-arid sahara.
4) The introduction of an elongated morphological trend from the Red Sea Hills area as Horn of Africa groups back-migrated into the Upper Nile.
I don't know when Evergreen will be back to see this, but where did he read about Red Sea Hills people migrating into the Upper Nile?
Posts: 7080 | From: Fallbrook, CA | Registered: Mar 2004
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To understand the change in african craniometric over time you must read Carlson and Gerven. You guys fail to understand many phenomena because you don't check the original articles mentioned in research papers.
Carlson and Gerven observed that the variance in craniofacial features in African populations may be due to diet( See: Carlson,D. and Van Gerven,D.P. (1979). Diffussion, biological determinism and bioculdtural adaptation in the Nubian corridor,American Anthropologist, 81, 561-580.)
. The research indicates that craniofacial features, in relation to the skull can be shaped, in evolutionary terms by heritability and high biomechanical load. This is reflected in the morphological heterogeneity within the same population studied by Carlson and Gerven when they studied Nubian craniometrics.
These researchers explained that the differences in Nubian skeletal remains was not the result of populaton changes resulting from invasion. They argued that the skeletal remains represented the same population.
So instead of the changes in crania reflecting biological diffusion, the changes in facial features result from changes in diet that lead to less masticatory stress associated with changes in subsistence patterns . Research shows that changes in diet lead to variation in the size and position of the muscles of mastication which inturn lead to reduction in the robustness of the craniofacial complex. This would explain why the use of multivariate techniques show variability between modern and ancient crania and skulls of African people and the broad or fine features associated with diverse African populations.
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