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Saturday, May 15th, 2004, 06:11 PM
Am J Phys Anthropol. 1995 Jan;96(1):25-38.

Anthropometric variation and the population history of Ireland.

Relethford JH, Crawford MH.

Department of Anthropology, State University of New York College, Oneonta 13820, USA.

Genetic variation among human populations can reflect a combination of contemporary patterns of gene flow and genetic drift as well as long-term population relationships due to population history. We examine the likely impact of past history and contemporary structure on the patterns of anthropometric variation among 31 counties in Ireland (made up of the two nations of the Republic of Ireland and Northern Ireland). Data for 17 anthropometric measures and parent-offspring migration on 7,214 adult Irish males were taken from the large data set originally collected by Dupertuis and Dawson in the mid-1930s (Hooton et al., 1955). Patterns of genetic similarity among 31 counties were assessed using R matrix methods that allow estimation of minimum genetic distances. These distances were compared to distances reflecting history, geography, and migration using matrix permutation methods. The results indicate that among-group variation in Ireland reflects past population history to a much greater extent than contemporary patterns of migration and population size. The midland counties are distinct from other populations, and their history suggests greater genetic input from early Viking invasions. A second major pattern in biological variation is a longitudinal gradient separating western and eastern counties. This gradient appears related to patterns of early settlement and/or a concentration in the east of later immigrants, particularly from England. Comparison of regional means with published data for several other European nations confirms these hypotheses.

Saturday, May 15th, 2004, 06:24 PM
Hum Biol. 1999 Oct;71(5):823-45. Related Articles, Links

Spatial variation of anthropometric traits in Ireland.

North KE, Crawford MH, Relethford JH.

Department of Anthropology, University of Kansas, Lawrence 66045, USA.

To further elucidate the relationship between geography and genetics in Ireland, we considered variation in anthropometric traits of adult males by town using spatial autocorrelation methods. By describing and distinguishing significant patterns of anthropometric variation, we determined whether the anthropometric traits display a simple pattern of spatial variation, as predicted by the isolation by distance model, or other patterns of spatial variation. Several hypotheses were examined, including (1) whether there was spatial patterning of 20 anthropometric phenotypic distributions and 7 principal components of Irish males and (2) if there was, whether these phenotypic distributions could be explained by a simple isolation by distance model. The results of this study can be summarized by several key findings: (1) There is significant spatial patterning among towns, as detected in correlograms of 14 anthropometric traits and 2 principal component factor scores (values of Moran's I ranging from 0.7510 to -0.3616, p < or = 0.0071); (2) 4 spatial patterns were detected, including clinical patterns, long-distance differentiation, distance distinction, and regional patchiness. These results suggest several likely causes of the observed spatial patterns. First, in Ireland patterns of anthropometric variation could not be explained by a single spatial pattern (i.e., isolation by distance). Second, through an examination of the various combinations of statistical homogeneity or heterogeneity, spatial patterning or nonpatterning, and similarity or dissimilarity of spatial patterns, we conclude that several migrational events structured the genetic landscape of Ireland.

Saturday, May 15th, 2004, 06:27 PM
Hum Biol. 1991 Apr;63(2):155-65.

Genetic drift and anthropometric variation in Ireland.

Relethford JH.
Division of Epidemiology, New York State Department of Health, Albany 12237.

The effect of genetic drift on the genetic structure of seven Irish populations was investigated using anthropometric data collected during the 1890s on 259 adult males. These populations ranged in size from 769 to 3757, were relatively stable over time, and were located within 119 km of one another. Two populations are known to have experienced considerable English admixture. Data on ten anthropometric variables (three body measures and seven craniofacial measures) were adjusted for age and used to compute a relationship (R) matrix. The R matrix was converted into a distance measure and compared with a potential genetic drift distance measure, defined as (1/Ni + 1/Nj), where Ni and Nj are the effective population sizes of groups i and j (derivation of this formula is presented). Distances were rank-transformed, and the correlation between their pairwise elements was computed using matrix permutation methods to assess significance. Under the hypothesis that drift affects anthropometric variation, these correlations are expected to be positive. The correlation between anthropometric distance and potential genetic drift distance is 0.123, which is not significantly different from 0 (P = 0.368). When a multiple regression model is used to adjust for geographic distance and English admixture, the partial correlation (0.369) is significant (p = 0.021). As part of further analysis of the genetic structure of these populations, the same analyses were repeated using a distance matrix derived from surname frequencies. The correlation of surname distance and potential genetic drift distance is 0.164, which is not significant (p = 0.264). When the multiple regression model is applied, the correlation is 0.401, which is borderline significant (p = 0.055). These results show the influence of genetic drift, local migration, and admixture on Irish population structure.

Saturday, May 15th, 2004, 06:30 PM
Am J Phys Anthropol. 1988 May;76(1):111-24.

Effects of English admixture and geographic distance on anthropometric variation and genetic structure in 19th-century Ireland.

Relethford JH.

Department of Anthropology, State University of New York College, Oneonta, New York 13820.

The analysis of anthropometric data often allows investigation of patterns of genetic structure in historical populations. This paper focuses on interpopulational anthropometric variation in seven populations in Ireland using data collected in the 1890s. The seven populations were located within a 120-km range along the west coast of Ireland and include islands and mainland isolates. Two of the populations (the Aran Islands and Inishbofin) have a known history of English admixture in earlier centuries. Ten anthropometric measures (head length, breadth, and height; nose length and breadth; bizygomatic and bigonial breadth; stature; hand length; and forearm length) on 259 adult Irish males were analyzed following age adjustment. Discriminant and canonical variates analysis were used to determine the degree and pattern of among-group variation. Mahalanobis' distance measure, D2, was computed between each pair of populations and compared to distance measures based on geographic distance and English admixture (a binary measure indicating whether either of a pair of populations had historical indications of admixture). In addition, surname frequencies were used to construct distance measures based on random isonymy. Correlations were computed between distance measures, and their probabilities were derived using the Mantel matrix permutation method. English admixture has the greatest effect on anthropometric variation among these populations, followed by geographic distance. The correlation between anthropometric distance and geographic distance is not significant (r = -0.081, P = .590), but the correlation of admixture and anthropometric distance is significant (r = 0.829, P = .047). When the two admixed populations are removed from the analysis the correlation between geographic and anthropometric distance becomes significant (r = 0.718, P = .025). Isonymy distance shows a significant correlation with geographic distance (r = 0.425, P = .046) but not with admixture distance (r = -0.052, P = .524). The fact that anthropometrics show past patterns of gene flow and surnames do not reflects the greater impact of stochastic processes on surnames, along with the continued extinction of surnames. This study shows that 1) anthropometrics can be extremely useful in assessing population structure and history, 2) differential gene flow into populations can have a major impact on local genetic structure, and 3) microevolutionary processes can have different effects on biological characters and surnames.

Saturday, May 15th, 2004, 06:34 PM
Ann Hum Biol. 1983 Jul-Aug;10(4):321-33.

Genetic structure and population history of Ireland: a comparison of blood group and anthropometric analyses.

Relethford JH.

Population structure and history may be studied on a local or a regional level. This paper examines the regional population structure of the Republic of Ireland and Northern Ireland with respect to population history and demographic processes. Blood-group and anthropometric data obtained from the literature are analysed. The blood-group data consist of ABO and Rhesus gene frequencies for 32 counties and the Aran Islands. Anthropometric data consist of summary statistics for 15 variables collected from 19 regions. The degree and pattern of population differentiation is assessed using new methods of population-structure analysis. Both blood group and anthropometric analyses show a west-east division of populations corresponding to the known history of inhabitation of Ireland, where successive waves of immigrants pushed earlier populations further west. In both analyses there were two deviations to this basic pattern: the Aran Islands and the midlands. In both cases, alternative historical explanations are examined. The genetic relationship of the Aran Islands to the rest of Ireland and England appears to be due to English admixture following the garrisoning of soldiers several centuries ago. The genetic position of the midlands is more complex, but suggests the effects of early Viking inhabitation. These findings are related to studies of the local, rather than regional, population structure of Ireland.