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The ancestry of modern Iberians (Spanish and Portuguese) is consistent with the geographical situation of the Iberian Peninsula in the south-west corner of Europe. There is a strong prehistoric connection particularly with Atlantic Europe, but also with the wider Mediterranean region, albeit the latter is lesser than regions to the East of the continent (the Balkans) due to Iberia being the farthest away from the Bosphorous region considered the main bridge of population expansions into Europe during the Neolithic. On the other hand, Iberia has the strongest genetic proximity in Europe to North Africa, although with strong regional variations. This purportedly results from northward population movements during the seven centuries of Muslim rule within the peninsula. The Basque Region in Northern Spain is genetically distinct as well as typically Atlantic European, holding the least Neolithic/Mediterranean and North African ancestry in Iberia. Modern day Basques are likely to be genetically similar to the Iberian peninsula's paleolithic inhabitants who repopulated Western Europe after the last Ice Age. == Population Genetics: Methods and Limitations == One of the first scholars to perform genetic studies was Luigi Luca Cavalli-Sforza. He used ''classical genetic markers'' to analyse DNA by proxy. This method studies differences in the frequencies of particular allelic traits, namely polymorphisms from proteins found within human blood (such as the ABO blood groups, Rhesus blood antigens, HLA loci, immunoglobulins, G-6-P-D isoenzymes, among others). Subsequently his team calculated genetic distance between populations, based on the principle that two populations that share similar frequencies of a trait are more closely related than populations that have more divergent frequencies of the trait. Since then, population genetics has progressed significantly and studies using ''direct DNA analysis'' are now abundant and may use mitochondrial DNA (mtDNA), the non-recombining portion of the Y chromosome (NRY) or autosomal DNA. MtDNA and NRY DNA share some similar features which have made them particularly useful in genetic anthropology. These properties include the direct, unaltered inheritance of mtDNA and NRY DNA from mother to offspring and father to son, respectively, without the 'scrambling' effects of genetic recombination. We also presume that these genetic loci are not affected by natural selection and that the major process responsible for changes in base pairs has been mutation (which can be calculated). Whereas Y-DNA and mtDNA haplogroups represent but a small component of a person’s DNA pool, autosomal DNA has the advantage of containing hundreds and thousands of examinable genetic loci, thus giving a more complete picture of genetic composition. Descent relationships can only to be determined on a statistical basis, because autosomal DNA undergoes recombination. A single chromosome can record a history for each gene. Autosomal studies are much more reliable for showing the relationships between existing populations but do not offer the possibilities for unraveling their histories in the same way as mtDNA and NRY DNA studies promise, despite their many complications. Genetic studies operate on numerous assumptions and suffer from methodological limitations such as selection bias and confounding. Phenomenon like genetic drift, foundation and bottleneck effects cause large errors, particularly in haplogroup studies. No matter how accurate the methodology, conclusions derived from such studies are compiled on the basis of how the author envisages their data fits with established archaeological or linguistic theories. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Genetic history of the Iberian Peninsula」の詳細全文を読む スポンサード リンク
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