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News: THE SEARCH FOR ATLANTIS IN CUBA
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the Saxons

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« Reply #15 on: May 02, 2007, 04:04:11 pm »

Admixture proportions were also evaluated by using a likelihood approach implemented by the program Lea [16]. This quantitative analysis was consistent with the visual pattern shown by PC investigation, and it also provides significant evidence that there has not been complete population replacement anywhere in the British Isles (see Table S1 in the Supplemental Data available with this article online).

The apportionment of genetic variation was inferred with AMOVA, as implemented by the Arlequin package [11]. Comparison of the different small towns sampled indicates that the vast majority of the diversity present was within populations (96.35%), with only 3.65% across populations. The subdivision of the samples into Celtic (Ireland, Wales, and mainland Scotland) versus the rest of the populations showed a distribution across the two groups of 3.65% of the total variation; the exclusion of Llanidloes and Durness, which clearly show evidence of continental input, increased this value to 6.16% ( Figure 3 and Table S1). Considering the indigenous/nonindigenous clustering system (Castlerea, Haverfordwest, and Llangefni versus the rest), a value of 7.48% was calculated, one of the highest values obtained, among multiple alternative clustering systems (not shown). Thus, the indigenous/nonindigenous distinction appears to be the most important factor influencing geographic patterns of Y chromosome variation in the British Isles.

In summary, our results show that Norwegian invaders heavily influenced the northern area of the British Isles, but this group had limited impact through most of mainland Scotland (except the extreme north). Instead, mainland Scotland was more influenced by the German/Danish input. Despite their well-known activities in the Irish Sea, Norwegian input in adjoining areas is modest. Some is indicated in the Isle of Man, and a smaller amount is indicated in Ireland. Perhaps the most surprising conclusion is the limited continental input in southern England, which appears to be predominantly indigenous and, by some analyses, no more influenced by the continental invaders than is mainland Scotland (Figure 3 and Table S1). It is interesting to note that the areas in southern England were, historically, mostly occupied by the Anglo-Saxons, while the activities of the Danish Vikings were mainly in eastern England [1]. The results seem to suggest that in England the Danes had a greater demographic impact than the Anglo-Saxons. An alternative explanation would be that the invaders in the two areas were genetically different and that we cannot see this difference reflected in the current inhabitants of the Continental areas corresponding to Anglo-Saxon and Danish homelands. This would seem to be a difficult distinction to make, and it should be emphasized that our analyses assume that we have correctly identified the source populations. If, for example, the real continental invaders had a composition more similar to the indigenous British than our candidate sample set, our results would systematically underestimate the continental input. Similarly, any Continental input into our Castlerea sample would bias our inferences, but the very similar composition of the Basque and Castlerea samples suggests that this has been minimal. With regard to source populations, we note that Weale et al. [7] recently used Friesland as an Anglo-Saxon representative source population and suggested a substantial replacement of pre-Anglo-Saxon paternal lineages in central England. We therefore compared Frisians to our North German/Danish sample and found that the two sets are not significantly different from each other (p = 0.3, data not shown). When included in the PC analysis, the Frisians were more “Continental” than any of the British samples, although they were somewhat closer to the British ones than the North German/Denmark sample. For example, the part of mainland Britain that has the most Continental input is Central England, but even here the AMH+1 frequency, not below 44% (Southwell), is higher than the 35% observed in the Frisians. These results demonstrate that even with the choice of Frisians as a source for the Anglo-Saxons, there is a clear indication of a continuing indigenous component in the English paternal genetic makeup. We also note that our analysis includes representatives of the Danish Vikings, which were not available in the Weale et al. study. Consideration of Danish Viking input is important because their activities on the British eastern coast are well documented [1]. Our evaluation of the Danish and Anglo-Saxon source populations, however, shows that the contributions of these groups are unlikely to be distinguishable by using the resolution available in our analyses. Whatever level of replacement took place in England, it could have been due to “Anglo-Saxons,” Danes, or a combination of both groups.

Conclusions

The detailed sampling scheme used here identified other previously unknown regional patterns in the degree of continental input. For example, the Central-Eastern part of England experienced the most continental introgression. In addition, our inclusion of samples from Wales additional to those of Weale et al. [7] indicates that the transition between England and Wales is somewhat gradual, which was not visible in the samples analyzed in the Weale et al. study

Most studies in human evolution and genetic history have used samples from very few locations, often near major metropolitan areas. Here, we show that detailed samples from multiple small, urban areas with a geographically structured sampling design reveal patterns that could not be detected with typical sampling schemes. For example, analyses of multiple sets have confirmed higher continental input in central England and the northernmost samples (Durness, on the north coast of Scotland and the Scottish Isles) and a lower level of continental introgression in southern England and Lowland Scotland. In addition, multiple sample sets revealed heterogeneity in Wales.

Iberian, French, and Central-Northern Italian populations have been shown to have similar Y chromosome compositions, presumably reflecting their common heritage in the European Palaeolithic [14]; Wilson et al. [4] noted that AMH+1 haplotypes at high frequency are associated with the European Palaeolithic. Here, we note that another haplogroup (I1b2) is found almost exclusively in British populations that have experienced little or no continental genetic input ( Tables 1 and S1). Intriguingly, earlier studies have shown that it is present in the Iberian Peninsula at low frequencies (0%–5.4%) and in Sardinia at a significant percentage (35.1%) [9 and 14]. This group might be another constituent of the European Palaeolithic.

Finally, we note that forensic analyses based on the Y chromosome generally assume homogeneity of Y chromosome haplotypes throughout most of Europe [17]. Our fine-scale investigation of Y chromosome variation demonstrates appreciable frequency differences of Y chromosome haplotypes over relatively short geographic distances. Haplotype 12 13 11 16 25 11 (hg R1a1) (number of repeats, loci as follows: DYS388, 393, 392, 19, 390, 391) is present at frequencies around 5% in Shetland and Orkney, while it is almost completely absent from the other collections. Similarly, haplotype 14 13 11 14 22 10 (hg IxI1b2) was recorded at 6%–7% in the Central-East English samples, but it was absent from Irish, Welsh, and Scottish populations.

Experimental Procedures

Microsatellite and UEP Analysis


Y chromosome microsatellites DYS388, 393, 392, 19, 390, and 391 analysis was performed by following the protocols described [12]. UEP analysis was based on a PCR-RFLP approach. Protocols will be published elsewhere and are available from C.C. upon request. Briefly, the DNA region containing the chosen polymorphic nucleotides was PCR amplified and then screened by using appropriate restriction endonucleases. Digested PCR products were loaded on a 377 ABI automated sequencer updated to 96 lanes, and alleles were called according to fragment size.

Data Analysis

Principal Components analysis was performed by using the POPSTR software (H. Harpending, personal communication). The apportionment of genetic variation and Fisher's Exact Test analog were inferred by using the Arlequin package [11].

Supplemental Data

Supplemental Data including Table S1 are available at http://images.cellpress.com/supmat/supmatin.htm.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VRT-48PV5SH-12&_coverDate=05%2F27%2F2003&_alid=339895807&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=6243&_sort=d&view=c&_acct=C000049116&_version=1&_urlVersion=0&_userid=949111&md5=9edf5ce1c39d4139af4c01733282fa82
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