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1Recent studies have produced a variety of advances in the investigation of genetic similarities and differences among human populations. Here, I pose a series of questions about human population-genetic similarities and differences, and I then answer these questions by numerical computation with a single shared population-genetic data set. The collection of answers obtained provides an introductory perspective for understanding key results on the features of worldwide human genetic variation.
Fifty unrelated Basque males from southwest Idaho were typed for the 17 Y-STR loci in the Yfiler multiplex kit (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635, YGATA H4.1 and DYS385a/b). In total, 42 haplotypes were identified, with no more than two individuals sharing a single haplotype. The haplotype diversity (HD) was 0.9935, and gene diversity (D) over loci was 0.457 ± 0.137. The Idaho Basque population was compared to the source population from the Basque autonomous region of Northern Spain and Southern France, as well as a United States Caucasian population. The haplotype diversity for the immigrant Basque sample is within 0.4% of the haplotype diversity of the European Basques (0.9903); thus the power of discrimination is similar for each population. The Idaho Basque population has less diversity in 9 out of 16 loci (considering DYS385a/b together) and 3% less diversity across all loci, compared to the European Basque population. A multidimensional scaling analysis (MDS) was created using pairwise RST values to compare the Idaho Basques to other populations. Based upon RST and FST measures, no significant differentiation was found between the Idaho and source European Basque population.
The 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, a direct relationship between NL thickness variation and the physical was trauma implied by the birth dynamics, the Caesarean, and the operative modes are apparently associated with 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 was 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.
The genetic surveys of the population of Britain conducted by Weale et al. and Capelli et al. produced estimates of the Germani immigration into Britain during the early Anglo-Saxon period, c.430–c.730. These estimates are considerably higher than the estimates of archaeologists. A possible explanation suggests that an apartheid-like social system existed in the early Anglo-Saxon kingdoms resulting in the Germani breeding more quickly than the Britons. Thomas et al. attempted to model this suggestion and showed that it was a possible explanation if all Anglo-Saxon kingdoms had such a system for up to 400 years. I noted that their explanation ignored the probability that Germani have been arriving in Britain for at least the past three millennia, including Belgae and Roman soldiers, and not only during the early Anglo-Saxon period. I produced a population model for Britain taking into account this long term, low level migration that showed that the estimates could be reconciled without the need for introducing an apartheid-like system. In turn, Thomas et al. responded, criticizing my model and arguments, which they considered persuasively written but wanting in terms of methodology, data sources, underlying assumptions, and application. Here, I respond in detail to those criticisms and argue that it is still unnecessary to introduce an apartheid-like system in order to reconcile the different estimates of Germani arrivals. A point of confusion is that geneticists are interested in ancestry, while archaeologists are interested in ethnicity: it is the bones, not the burial rites, which are important in the present context.