The influence of artificial cranial deformation on discontinuous morphological traits
01 Nov 1970-American Journal of Physical Anthropology (Wiley Subscription Services, Inc., A Wiley Company)-Vol. 33, Iss: 3, pp 357-371
TL;DR: The findings suggest that deformed crania should be excluded from population studies in which genetic divergence between groups is estimated in terms of cranial trait frequencies.
Abstract: Following the elucidation by geneticists of the nature of minor skeletal variants in the mouse, anthropologists have stressed the potential of these traits for tracing the affinities and movements of extinct human populations. Earlier Sullivan observed that discrete traits could be particularly valuable where artificial cranial deformation limits the use of craniometry.
Twenty-eight minor variants were studied in bifronto-occipitally deformed and undeformed skulls of a sample of 78 from a single Hopewell mound. The pattern of frequency differences between deformed and undeformed with respect to traits at the back of the vault and in the frontal region, interpreted in developmental terms, reveals a hypostotic effect in these regions in the deformed skull; while, in contrast, traits of the lateral vault, facial skeleton and cranial base point to a general hyperostotic effect in these regions. Each of three emissaria tends to be more constant in the deformed.
That minor cranial variants manifest a plastic response to this type of environmentally-imposed stress is consistent with the nature of such variants as elucidated by genetics research in mice. The findings suggest that deformed crania should be excluded from population studies in which genetic divergence between groups is estimated in terms of cranial trait frequencies.
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TL;DR: It is concluded, on the basis of these findings, that discrete traits in isolation are not of paramount value to skeletal genetic studies, but may be vital in comparison and conjunction with other types of data in analyzing the population genetics of extinct groups.
Abstract: Discrete traits are of increasing interest in comparative skeletal biological research. Characteristics justifying their use have been investigated primarily in mice, however. Using 72 discrete variants, 321 human skulls from the Terry Collection of known race, sex and age have been studied. Significant sex and age differences were detected. Inter-trait correlation was found to be at a low but significant overall level. Multivariate comparison with conventional craniometric analysis was undertaken on subdivisions of the sample, and distance based on metric and nonmetric data were concordant. It is concluded, on the basis of these findings and the discontinuous variant frequency distributions, that discrete traits in isolation are not of paramount value to skeletal genetic studies, but may be vital in comparison and conjunction with other types of data in analyzing the population genetics of extinct groups.
197 citations
TL;DR: Clinical and experimental data are found to support strongly the hypothesis that there is a causative relationship between the formation of auditory exostoses and exploitation of resources in cold water, particularly through diving.
Abstract: The frequency of auditory exostoses was examined by latitude. It was found that discrete bony lesions of the external auditory canal were, with very few exceptions, either absent or in very low frequency (< 3.0%) in 0–30°N. and S latitudes and above 45°N. The highest frequencies of auditory exostoses were found in the middle latitudes (30–45°N and S) among populations who expoit either marine or fresh water resources. Clinical and experimental data are discussed, and these data are found to support strongly the hypothesis that there is a causative relationship between the formation of auditory exostoses and exploitation of resources in cold water, particularly through diving. It is therefore suggested that since auditory exostoses are behavioral rather than genetic in etiology, they should not be included in estimates of population distance based on nonmetric variables.
130 citations
TL;DR: The principal-coordinate and neighbor-joining analyses of Smith's mean measure of divergence (MMD), based on trait frequencies, indicate that the clustering pattern is similar to those based on classic genetic markers, DNA polymorphisms, and craniometrics, and significant interregional separation and intraregional diversity are present in Subsaharan Africans.
Abstract: In the present study, the frequency distributions of 20 discrete cranial traits in 70 major human populations from around the world were analyzed. The principal-coordinate and neighbor-joining analyses of Smith's mean measure of divergence (MMD), based on trait frequencies, indicate that 1). the clustering pattern is similar to those based on classic genetic markers, DNA polymorphisms, and craniometrics; 2). significant interregional separation and intraregional diversity are present in Subsaharan Africans; 3). clinal relationships exist among regional groups; 4). intraregional discontinuity exists in some populations inhabiting peripheral or isolated areas. For example, the Ainu are the most distinct outliers of the East Asian populations. These patterns suggest that founder effects, genetic drift, isolation, and population structure are the primary causes of regional variation in discrete cranial traits. Our results are compatible with a single origin for modern humans as well as the multiregional model, similar to the results of Relethford and Harpending ([1994] Am. J. Phys. Anthropol. 95:249-270). The results presented here provide additional measures of the morphological variation and diversification of modern human populations.
130 citations
Additional excerpts
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TL;DR: The results of a new skull simplification metric (SSM), which is defined as a function of the number of distinct elements, show that pronounced simplification is evident on both temporal and phylogenetic scales.
Abstract: The prevalence and meaning of morphological trends in the fossil record have undergone renewed scrutiny in recent years. Studies have typically focused on trends in body size evolution, which have yielded conflicting results, and have only rarely addressed the question as to whether other morphological characteristics show persistent directionality over long time scales. I investigated reduction in number of skull and lower jaw bones (through loss or fusion) over approximately 150 million years of premammalian synapsid history. The results of a new skull simplification metric (SSM), which is defined as a function of the number of distinct elements, show that pronounced simplification is evident on both temporal (i.e., stratigraphic) and phylogenetic scales. Postcranial evolution exhibits a similar pattern. Skull size, in contrast, bears little relationship with the number of distinct skull bones present. Synapsid skulls carried close to their observed maximum number of elements for most of the La...
128 citations
Cites background from "The influence of artificial cranial..."
...Although skull growth has been shown to have an effect on skull bone number in some developmental studies (e.g., Coulombre et al. 1962; Ossen- berg 1970), adult skull size in fossil synapsids has little relationship with skull bone number....
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TL;DR: This work test the hypothesis that fronto-occipital artificial reshaping of the neurocranial vault results in specific changes in the cranial base and face, and finds that important differences may exist in the morphological effects of frontoscipital reshaping from one group to another.
Abstract: Artificial reshaping of the cranial vault has been practiced by many human groups and provides a natural experiment in which the relationships of neurocranial, cranial base, and facial growth can be investigated. We test the hypothesis that fronto-occipital artificial reshaping of the neurocranial vault results in specific changes in the cranial base and face. Fronto-occipital reshaping results from the application of pads or a cradle board which constrains cranial vault growth, limiting growth between the frontal and occipital and allowing compensatory growth of the parietals in a mediolateral direction. Two skeletal series including both normal and artificially modified crania are analyzed, a prehistoric Peruvian Ancon sample (47 normal, 64 modified crania) and a Songish Indian sample from British Columbia (6 normal, 4 modified). Three-dimensional coordinates of 53 landmarks were measured with a diagraph and used to form 9 finite elements as a prelude to finite element scaling analysis. Finite element scaling was used to compare average normal and modified crania and the results were evaluated for statistical significance using a bootstrap test. Fronto-occipitally reshaped Ancon crania are significantly different from normal in the vault, cranial base, and face. The vault is compressed along an anterior-superior to posterior-inferior axis and expanded along a mediolateral axis in modified individuals. The cranial base is wider and shallower in the modified crania and the face is foreshortened and wider with the anterior orbital rim moving inferior and posterior towards the cranial base. The Songish crania display a different modification of the vault and face, indicating that important differences may exist in the morphological effects of fronto-occipital reshaping from one group to another.
120 citations
References
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Journal Article•
642 citations
Book•
01 Jan 1963
TL;DR: Almost without exception the conditions whose developmental pathology been studied have been selected for the simplicity of the genetical situation so as to avoid unnecessary complications.
Abstract: Almost without exception the conditions whose developmental pathology been studied have been selected for the simplicity of the genetical situation so as to avoid unnecessary complications". This sentence from the preface adequately reflects the viewpoint from which the book has been written. Veterinary readers seeking information on domestic species will be disappointed to find that 90% of the animals are Other CABI sites
180 citations
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168 citations
TL;DR: In this paper, a comparison between the incidences of skeletal variants in house mouse populations collected from: corn ricks on a single farm in Hampshire; eleven separated localities in different parts of the British Isles; and nine other places throughout the world.
Abstract: It has been suggested (Berry & Searle, 1963) that the discontinuous (‘quasi-continuous’) variants studied by Gruneberg et al. in the skeleton of rodents can be regarded as constituting epigenetic polymorphism in different populations. Comparisons have been made between the incidences of skeletal variants in house mouse populations collected from: corn ricks on a single farm in Hampshire; eleven separated localities in different parts of the British Isles; and nine other places throughout the world. These showed that the method could profitably be used for genetically characterizing and hence comparing populations. There was evidence suggestive of genetical drift between local populations and stabilizing selection over a larger area.
133 citations
128 citations