No abstract

Chloroplast PCR-RFLP markers were used to reconstruct the history of the silver birch, Betula pendula Roth, in Europe since the last glacial maximum (LGM). In birch, fossil pollen maps do not reveal a clear chronological sequence of postglacial spread. If anything, the pollen record suggests that most of Europe was recolonized by birches as early as 10000 bp, probably from populations that remained close to the ice sheets during the LGM. The geographical distribution of haplotypes supports a scenario of early colonization. Two of the 13 haplotypes that were observed are common, representing 35% and 49% of the total sample, respectively. Although one of the common haplotypes is predominant in the NW and the other in the SE, both are present throughout most of the investigated geographical area. Rare haplotypes are geographically restricted. The distribution of the haplotypes reveals five genetic boundaries between groups of haplotypes and allows us to infer patterns of postglacial recolonization. Europe was re-occupied by two main waves of recolonization: one eastern and one western, with origins at intermediate latitudes. Populations in the Iberian Peninsula and in Italy did not take part in the postglacial recolonization of Europe.

ABTRACTThe transition from an intra-to extra-uterine environment leaves its mark in deciduous teeth (and first permanent molars) as an accentuated enamel incremental ring called the neonatal line (NL). This prominent microfeature separates the enamel formed during intrauterine life from that formed after leaving the womb. However, while the physical structure of this scar is well known, the bases of its formation are still a matter of investigation. In particular, besides the influence of the birth-related abrupt environmental and dietary changes and the role played by physiological factors such as hypocalcaemia, it has been suggested a direct relationship between NL thickness variation and the physical trauma implied by the birth dynamics, the Caesarean and the operative modes being apparently associated to the thinnest and the thickest lines, respectively. By using the histological record from a deciduous dental sample (exfoliated crowns) of 100 modern healthy school-aged children (47 males and 53 females) of reported birth histories (normal delivery mode: 55 cases; Caesarean: 40; operative: 5), we investigated the relationships between birth dynamics and NL thickness variation. The Tukey Honest Significant Difference method has been used to test the differences between the means of the grouping levels. The results of our histo-morphological investigation do not support the suggestion that Caesarean-born children display, on average, a thinner enamel scar compared to children associated to a normal delivery mode. Rather, our study points to the influence exerted by factors intimately related to gestational length variation on the degree of expression of the line. KEY WORDS: HUMAN BIRTH, DELIVERY MODE, GESTATION LENGTH, DECIDUOUS TEETH, DENTAL ENAMEL STRUCTURE, INCREMENTAL MARKERS, NEONATAL LINE.Pre-print version. Visit http://digitalcommons.wayne.edu/humbiol/ after 1 December 2011 to acquire final version. 2The birth process leaves its mark on dental enamel in the form of a ring, an accentuated incremental line called the "Neonatal Line" (NL) (Rushton 1933;Schour 1936). This prominent microfeature, occasionally visible also in the dentine (Schour 1936;Skinner 1992), separates the enamel formed during intrauterine life from that formed after leaving the womb.In modern humans, the NL is usually present in all crowns forming at birth, that is, all the elements of the primary dentition and the first permanent molars (mesiobuccal cusp) (Christensen and Kraus 1965, Deutsch andPe'er 1982;Deutsch et al. 1985;Kraus 1959;Levine et al. 1979). Occasionally, a macroscopic hypoplasia can be detected in correspondence with the NL, but it is usually worn away (Massler et al. 1941;Moss-Salentijn and Hendricks-Klyvert 1985;Schroeder 1991;Skinner 1992).At birth, the enamel is only partially mineralized and continues to increase in thickness by apposition of additional centripetal layers secreted by the ameloblasts at the level of the enamel-dentine junction (EDJ) to a circadian rhythm of 4-5 µm in extant humans (Antoine et al. 2...

Abstract. Dialectometry produces aggregate distance matrices in which a distance is specified for each pair of sites. By projecting groups obtained by clustering onto geography one compares results with traditional dialectology, which produced maps partitioned into implicitly non-overlapping dialect areas. The importance of dialect areas has been challenged by proponents of continua, but they too need to compare their findings to older literature, expressed in terms of areas.Simple clustering is unstable, meaning that small differences in the input matrix can lead to large differences in results (Jain et al. 1999). This is illustrated with a 500-site data set from Bulgaria, where input matrices which correlate very highly (r = 0.97) still yield very different clusterings. Kleiweg et al. (2004) introduce composite clustering, in which random noise is added to matrices during repeated clustering. The resulting borders are then projected onto the map.The present contribution compares Kleiweg et al.'s procedure to resampled bootstrapping, and also shows how the same procedure used to project borders from composite clustering may be used to project borders from bootstrapping.

Several studies showed that surnames are good markers to infer patrilineal genetic structures of populations, both on regional and microregional scales. As a case study, the spatial patterns of the 9,929 most common surnames of the Netherlands were analyzed by a clustering method called self-organizing maps (SOMs). The resulting clusters grouped surnames with a similar geographic distribution and origin. The analysis was shown to be in agreement with already known features of Dutch surnames, such as 1) the geographic distribution of some well-known locative suffixes, 2) historical census data, 3) the distribution of foreign surnames, and 4) polyphyletic surnames. Thus, these results validate the SOM clustering of surnames, and allow for the generalization of the technique. This method can be applied as a new strategy for a better Y-chromosome sampling design in retrospective population genetics studies, since the idenfication of surnames with a defined geographic origin enables the selection of the living descendants of those families settled, centuries ago, in a given area. In other words, it becomes possible to virtually sample the population as it was when surnames started to be in use. We show that, in a given location, the descendants of those individuals who inhabited the area at the time of origin of surnames can be as low as approximately 20%. This finding suggests 1) the major role played by recent migrations that are likely to have distorted or even defaced ancient genetic patterns, and 2) that standard-designed samplings can hardly portray a reliable picture of the ancient Y-chromosome variability of European populations.