Genetic history of Europe

The genetic history of Europe is complicated because European populations have a complicated demographic history, including many successive periods of population growth. The history must be inferred from the patterns of genetic diversity across continents and time. The primary data come from sequences of , Y-chromosome, and autosomal DNA (including single-nucleotide polymorphisms) from modern populations and if available from ancient DNA.

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, , immunoglobulins, G6PD 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.

From this, he constructed phylogenetic trees that showed genetic distances diagrammatically. His team also performed principal component analyses, which is good at analysing multivariate data with minimal loss of information. The information that is lost can be partly restored by generating a second principal component, and so on. In turn, the information from each individual principal component (PC) can be presented graphically in synthetic maps. These maps show peaks and troughs, which represent populations whose gene frequencies take extreme values compared to others in the studied area.

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