Y chromosomes in surname samples: insights into surname frequency and origin. F. Calafell, N. SolÚ-Morata, J. Bertranpetit, D. Comas Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Barcelona, Spain.

   In most societies, surnames are inherited through the paternal line, exactly as Y chromosomes are, with the exceptions of adoption, false paternity, and the inheritance of the maternal surname (as in the case of single mothers). The well-established phylogeography of the Y chromosome and the existence of fast-evolving STR markers implies that genotyping the Y chromosomes in samples of men bearing the same surname allows to i) count the number of founders of a surname and the frequency of their descendant in the current population and ii) pinpoint the remote origins of the founder of a surname. We have collected >2,500 samples from volunteers bearing one of 50 different Catalan surnames (http:// http://cognoms.upf.edu/), in which we are genotyping 17 Y-chromosome STRs and a custom-designed set of 64 SNPs (typed in a single reaction with the OpenArray Real-Time PCRplatform), with the following objectives: i)Discover and quantify the processes that drive surname frequency. Surname polyphiletism (which can be measured from the number of founders detected from the Y chromosome diversity) can drive surname frequency, as was found in a sample of English surnames, but drift and natural selection (associated with high-status surnames) may also have a role. 2) Were the founders of surnames that are linguistically Arab or Hebrew North Africans or Jews themselves? 3) Were the founders of Germanic patronymic surnames of a different genetic origin form the rest of the population? In Catalonia, as in France, a frequent source of surnames are former first names of Germanic origin (Albert, Robert, Grau,...). We will compare some of those to patronymic surnames of Latin origin (Oriol, Pons,...). Haplogroup frequency differences between Germany and Catalonia provide sufficient power for this comparison. 4) Does an ethnonymic surname indicate a foreign origin? Some Catalan surnames (Alemany, DanÚs, Guasch) denote geographic origin (they mean German, Dane, Gascon, respectively). We have completed this objective and we have found that haplogroups that are more frequent in Germany or Gascoigne than in Catalonia were not overrepresented in the founders of the Alemany and Guasch surnames. Thus, these surnames may have originated as bynames not necessarily linked with the origins of the founders.

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