The use of non-metrical variations of the cranium in the study of Scandinavian population movements

The composition of the founding population of Iceland: A new perspective from 3D analyses of basicranial shape

The settlement of Iceland in the Viking Age has been the focus of much research, but the composition of the founding population remains the subject of debate. Some lines of evidence suggest that almost all the founding population were Scandinavian, while others indicate a mix of Scandinavians and people of Scottish and Irish ancestry. To explore this issue further, we used three-dimensional techniques to compare the basicrania of skeletons from archaeological sites in Iceland, Scandinavia, and the British Isles. Our analyses yielded two main results. One was that the founding population likely consisted of roughly equal numbers of Scandinavians and people from the British Isles. The other was that the immigrants who originated from the British Isles included individuals of southern British ancestry as well as individuals of Scottish and Irish ancestry. The first of these findings is consistent with the results of recent analyses of modern and ancient DNA, while the second is novel. Our study, therefore, strengthens the idea that the founding population was a mix of Scandinavians and people from the British Isles, but also raises a new possibility regarding the regions from which the settlers originated.

The configuration of cervical spinous processes in black and white South African skeletal samples

The present study investigates the frequency of bifidity/nonbifidity in the black and white South African populations. Four-hundred skeletons of known race, sex, and tribal group were examined. Spinous processes were classified as bifid (bifurcate and cleft subtypes) and nonbifid (obtuse, pediculate, acinate, and clavate subtypes). Statistical analysis using the chi-squared probability test (p < 0.05) was carried out. Bifid spinous processes were present significantly more frequently in the white sample (58.9%) than in the black (31.6%). A bifid spinous process occurred most commonly in C2 (89%) followed by C5 (83%), C4 (79%), C3 (59.4%), and C6 (41.7%) in the white sample. A similar order of decrease in bifidity occurred in the black sample. C2 most commonly displayed the bifurcate subtype of spinous process, while the clavate subtype of nonbifid spinous process was the most common in both populations. The significantly higher frequency of bifidity in the white South African sample when compared to the black sample may suggest a population difference.

Why did the frequency of palatine torus increase in the ancient Anatolian populations?

The frequency of the palatine torus varies in various populations from different regions of the world. In this study, the change of frequency of palatine torus is examined using 387 skulls from 12 different ancient Anatolian populations in various periods ranging from the Early Bronze Age to the first quarter of the 20th century. While the frequency of palatine torus is 45% in the Early Bronze Age, this ratio steadily increases to 87% in the Ottoman Period and finally declines to 40% during the recent period. It was determined that the increase in the frequency of the palatine torus is statistically significant across different periods from the Early Bronze Age until the 20th century. Constituting a passageway between Asia and Europe and being located on the crossroads of the most important trade route of the Medieval Period, the Silk Road, Anatolia is known to have been subjected to recurring invasions and migrations since the 11th century A.D. Therefore, it is possible to say that, with the introduction of the Mongoloid influence in Anatolia, genetic flow has had a significant role in the observed increase in the frequency of this trait.

Why are rare traits unilaterally expressed?: Trait frequency and unilateral expression for cranial nonmetric traits in humans

Based on an analysis of nonmetric trait databases from several large skeletal series in Northern Europe and South America, representing 27 bilateral traits, we report a predictable relationship between the frequency of nonmetric traits and the probability that they are expressed bilaterally. In a wider sampling of traits and populations, this study thus confirms the findings of an earlier study by Ossenberg ([1981] Am. J. Phys. Anthropol. 54:471-479), which reported the same relationship for two mandibular traits. This trend was previously explained by extending the multifactorial threshold model for discontinuous traits to incorporate either separate thresholds for unilateral or bilateral expression, or by a fuzzy threshold in which the probability of bilateral expression increases away from the median threshold value. We show that the trend is produced under the standard multifactorial threshold model for discontinuous traits simply if the within-individual or developmental instability variance remains relatively constant across the range of liability. Under this assumption, the number of individuals in which one side but not the other is pushed over the threshold for trait formation will be a larger proportion of the number of individuals expressing the trait when the trait frequency is low. As trait frequency increases, the significance of within-individual variance as a determinant of trait formation decreases relative to the genetic and among-individual environmental variance. These results have implications for interpreting nonmetric trait data as well as for understanding the prevalence of unilateral vs. bilateral expression of a wide variety of discontinuous traits, including dysmorphologies in humans.

Composition of the founding population of Iceland: biological distance and morphological variation in early historic Atlantic Europe

We examined the composition of the founding population of Iceland through the study of morphological traits in skeletons from Iceland, Ireland, Norway, and Greenland. This is the first study to address this issue from the Settlement Period of Iceland and contemporary samples from Ireland. We pose the following questions: 1) Was the founding population of Iceland of mixed or homogeneous origin? 2) Is there evidence for a significant Irish cohort in the founding population, as suggested in medieval Icelandic literature? Analysis of biodistance revealed that both Settlement Age and later samples from Iceland showed a greater degree of phenetic similarity to contemporary Viking Age Norwegians than to samples obtained from early medieval Ireland. Analysis of among-individual morphological variation showed that the Settlement Age population of Iceland did not exhibit an increase in variation in comparison to other populations in the sample, suggesting a relatively homogenous origin. However, estimation of admixture between the Irish and Norwegian populations indicated that 66% of the Icelandic settlers were of Norwegian origin. Comparison of the Icelandic samples to hybrid samples produced by resampling the Viking Age Norwegian and early medieval Irish samples revealed that the Icelandic samples are much closer to the Norwegian samples than expected, based on a 66:34 mixture of Norwegian and Irish settlers. We conclude that the Settlement Age population of Iceland was predominantly (60-90%) of Norwegian origin. Although this population was relatively homogenous, our results do not preclude significant contributions from Ireland as well as other sources not represented in our analysis.

Cranial variation in the Marquesas Islands

The Marquesas Islands have traditionally been divided into a northwestern and a southeastern group, a division which reflects language dialect differences. Additionally, archaeological studies have also suggested that differences in material culture existed between the northwestern and southeastern islands. This study examines Marquesan cranial discrete and metric traits to evaluate the level of intra-archipelago heterogeneity, and to determine if a northwest/southeast division is evident cranially. The data consist of 28 cranial discrete traits and 49 craniofacial measurements of prehistoric Marquesans. Male and female data are pooled for discrete trait and metric data, following a Z-score standardization technique adjustment. The data represent three island samples: Nuku Hiva (northwest), Fatuiva (southeast), and a combined Tahuata/Hiva 'Oa (southeast). Of the 28 discrete traits, 16 are utilized in a mean measure of divergence analysis that provides scores of 0.259 for Fatuiva-Tahuata/Hiva 'Oa, 1.850 for Nuku Hiva-Fatuiva, and 1.491 for Nuku Hiva-Tahuata/Hiva 'Oa. Of the 49 craniofacial measurements, 46 are utilized in RMET/NORM analyses, providing unbiased D(2) values of 0.0433 for Fatuiva-Tahuata/Hiva 'Oa, 0.1328 for Nuku Hiva-Fatuiva, and 0.0813 for Nuku Hiva-Tahuata/Hiva 'Oa. The islands of the southeastern group are closer to each other than either was to the island of the northwestern group. When a sample from 'Ua Huka is included in the craniometric analysis, the unbiased D(2) values of 0.0829, 0.1175, and 0.0431 are calculated for 'Ua Huka and Nuku Hiva, and Fatuiva and Tahuata/Hiva 'Oa pairings, respectively, indicating a close similarity of 'Ua Huka to the southeastern islands. Mean measure of divergence analysis of cranial discrete traits as well as RMET/NORM analyses of craniometric variables reveal that differences exist between the islands of the northwestern and southeastern Marquesas Islands. These results support previous research that documented linguistic and cultural differences between these regions of the archipelago. However, the results indicate that 'Ua Huka, an island traditionally included in the northwestern Marquesas Islands, has an affinity to the southeastern Marquesas Islands, possibly due to its pivotal position as a waypoint in the Marquesas Island interaction sphere.

Palatine torus in the Greenlandic Norse

Physical anthropologists have long been intrigued by the distinctive oral tori expressed by the medieval Norse populations of Iceland and Greenland. To assess the temporal and spatial variation of one form of oral tori, palatine torus, observations were made on all available Greenlandic Norse skeletons, as well as on samples of medieval Icelanders and Norwegians. In terms of temporal variation, 12th to 14th century (medieval) Greenlanders from the Eastern and Western settlements exhibited higher frequencies and more pronounced expressions of palatine torus compared with early 11th century Greenlanders. The early Greenlandic sample closely approximated the medieval Icelandic and Norwegian samples for total torus frequency, although the Norwegians exhibited the trait to a less pronounced degree. As degree of expression is the most distinctive aspect of torus variation among the Norse, some combination of environmental factors, including increased masticatory stress and chronic undernutrition, probably accounts for most of the difference between settlement period and medieval Greenlanders. Although palatine torus may be hereditary in part, environmental factors play a significant role in the expression of this trait.

The relationship between auditory exostoses and cold water: a latitudinal analysis

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 (less than 3.0%) in 0-30 degrees N and S latitudes and above 45 degrees N. The highest frequencies of auditory exostoses were found in the middle latitudes (30-45 degrees N and S) among populations who exploit 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.

The use of nonmetric variation in estimating human population admixture: a test case with Brazilian blacks, whites, and mulattos

Measurements in populations which serve as valid indicators of biological relationship should be proportional to genetic distance. In order to test the utility of discrete cranial traits for estimating genetic distances among populations, estimates of admixture are obtained for gene frequency data and nonmetric cranial data in São Paulo mulattos (M). The gene frequency data serve as a control that the three populations are related as stated: estimates of admixture are obtained by using São Paulo whites (W) and blacks (B) as parental populations and by estimating the parameter of admixture, m, in the model pM = (1 - m) pW + mpB (Elston, 1971) where the p's are either gene frequencies or nonmetric trait frequencies. A test of goodness of fit of the model provides a means of ascertaining whether or not the data fit this linear model. While the gene frequency data indicate distances among the three populations which are highly compatible with the linear model of admixture, the nonmetric data show significant deviations from the model. This implies that the frequencies of the nonmetric traits in the populations used in this analysis are not a linear function of genetic distance. This discourages the use of nonmetric traits in making quantitative conclusions about genetic relationships. It also suggests the need for investigation of the use of other skeletal characters for estimating genetic distance, as well as approaches for such investigations through the study of hybrid individuals.

Effects of protein-calorie malnutrition during suckling and post-weaning periods on discontinuous cranial traits in rats

The influences of protein-calorie malnutrition (PCM), and sex during lactation and post-lactation on the frequencies of 25 discontinuous cranial traits (DCT), were investigated in Holtzman rats. Significant differences were observed in about 20% of the traits. Those traits were: the interfrontal fusion, the posterior incurvation of the palatine border, the double maxillary foramen, the double posterior palatine foramen, and the double frontal foramen. Total PCM was the nutritional factor which showed the greatest influence on the variability of the DCTs. It was followed, in decreasing order, by the PCM imposed during post-lactation and lactation. Sex had more influence than early PCM but less than late PCM. It is concluded that despite their apparent stability, a substantial number of DCTs were altered by both biological (like sex) and environmental factors (like nutritional deficiencies) imposed at different stages of postnatal development.

The assessment and meaning of intraobserver error in population studies based on discontinuous cranial traits

Intraobserver scoring precision of 50 discontinuous (discrete) cranial traits was assessed on a sample of 125 intact Iroquois crania using the square of the phi coefficient. Scoring consistency was high for most traits although several were subject to low precision (phi 2 less than 0.7). Most errors were random rather than systematic. Taken collectively the problematic traits exceeded their expected contribution to MMD coefficients among four Woodland samples from southern Ontario. A traitlist with the problematic variants excluded produced more meaningful biological relationships among the samples. Further, the % contribution of the problematic traits increased with the time interval between the scoring of the individual samples. It was suggested that intraobserver error could effectively distort the interpretation of biological relationships and that it must in part be responsible for the poor performance reported for discontinuous traits in some studies. Therefore, it was argued that the results support rather than compromise the use of discontinuous skeletal traits in population studies and that the assessment of intraobserver error should be a standard procedure of the research design.

A family study of two skeletal variants: atlas bridging and clinoid bridging

The frequency of two non-metric skeletal traits, atlas bridging and clinoid bridging, were examined serially in a randomly chosen sample of 147 families who participated in the Burlington Growth Study. The sample is representative of an Ontario white Anglo-Saxon population. Partial and complete atlas briging occurred in 29.2% of the sample, partial and complete clinoid bridging in 15.2%. Atlas bridging appears at an average age of 10.7 years, clinoid bridging at seven years, demonstrating that these characters are not simply expressions of soft tissue sclerosis in old age. Both traits show no strong associations with bone robusticity although atlas bridging is slightly more frequent in males. Both traits are more frequent in relatives of affected individuals than in the sample as a whole. Correlations between parents and offspring and between sibs are highly significant for atlas bridging, less so far clinoid bridging. These traits should fit either a single gene or quasi-continuous, polygenic model of inheritance. Several tests for polygenic inheritance such as the correlation between first and second born sibs' trait condition, the relationship between trait expression in offspring and total trait incidence in affected parents, and the correlation between trait frequency and expressivity on an intergroup basis were all positive for atlas bridging. The evidence for polygenic inheritance of clinoid bridging is weaker but suggestive. The results obtained in this study for atlas bridging are comparable to data from one earlier family study. The evidence suggests that these two traits should prove useful as genetic markers in skeletal population studies although there is still need for careful control over trait observation and description. Future research should attempt to measure non-metric traits continuously when their underlying distributions are known to be graded.

Within and between race distances in population studies based on discrete traits of the human skull

A battery of 24 discrete cranial traits has been tested for its power to discriminate within- and between-race distances for the two principal North American indigenous populations: Indian (7 samples, N = 366) and Eskimo (7 samples, N = 451). One of the Indian samples, Dakota Sioux, has been split according to tribal subdivisions, the intra-tribal mean distance providing a parameter of very close relationship. In addition, two Negro samples provide a parameter of relationship phylogenetically remote from the Amerinds. Separate male-female analysis of the three largest samples indicates that distances for pooled samples are not seriously affected by the sex component. Within-race distances (C. A. B. Smith's Measure of Divergence, MD), are smaller than between-race at the .00001 level of significance (Mann-Whitney U test) for both Indian-Eskimo and Amerind-Negro comparisons. The features most powerful for Indian-Eskimo and Amerind-Negro comparisons. The features most powerful for Indian-Eskimo discrimination are revealed by their percent contribution to the mean of 49 MD's. The African heritage of American Blacks is reflected in a characteristic Negro pattern of trait frequencies different from the Amerind. This battery of features yields valid taxonomical information useful in conjunction with other physical data to reconstruct affinities of extinct populations.

The anthropological value of minor variants of the dental crown

The incidences of 31 minor variants of the dental crown were scored from dental casts of samples taken from six European populations. Although several variants showed significant sex bias in one or other sample, only one (pits instead of furrow on premolar2) consistently favoured one sex. Associations between the variants were sought. Although few consistent associations were demonstrated, there was a possible tendency for extra cusps to occur together throughout the dentition. Distance statistics calculated between the samples were compatible with the expected genetical relationships of the samples, but only modern samples could be used since variants were destroyed by attrition in archeological samples. Before such distances can be considered reliable, it is necessary to know: (i)the extent to which environmental factors such as diet influence variant expression. (ii)whether or not variant bearing teeth are selectively destroyed by caries, which in civilised populations render a high proportion of most dentitions unscoreable.

The natural history of man in Shetland

The Shetland Islands lie in the North Atlantic approximately equi-distant between Scotland, Norway and the Faroes. The earliest known colonizers came from the Mediterranean, but when the Vikings arrived (c. AD 800), there seem to have few or no human inhabitants. The descendants of the west Scandinavians who came to the islands in the early Viking movement still comprise the bulk of the human population, and form a series of isolates unique in the United Kingdom.

The paper summarizes the available information on the origins and physical characteristics of the Shetlanders. Much of this is trivial, but in the absence of any other review we have brought together what is known. The only blood group data are ABO frequencies which are similar to those on the other North Atlantic islands (Orkney, Faroe and Iceland). The best estimates of relationship are based on comparisons of non-metrical skull variant frequencies which show that the nearest relatives of the Shetlanders are the inhabitants of Jaeren in southern Norway. The same conclusion comes from independent evidence of linguistic affinities.

Shetland has the highest known prevalence of multiple sclerosis in the world, and possibly a high incidence of gastric ulceration. It also has a large number of standard Down's syndrome (trisomy-21) patients. These could be the result of the fathers' periodic absences at sea, resulting in their families being spread over a large span of years. Clearly there are interesting and possibly important morbidity and mortality factors operating in the population—which could give significant information about genetical factors in disease. Data on mental defect and psychiatric disease are also presented.