(IsraelNN.com) Twenty percent of the population of the Iberian Peninsula has Sephardic Jewish ancestry and 11 percent have Arab or Berber ancestors, geneticists have found. The genetic signatures of people in Spain and Portugal provide "new and explicit evidence of the mass conversions of Sephardic Jews and Muslims to Catholicism in the 15th and 16th centuries," following the expulsion of the Jews and Muslims from that country.

The research was carried out by a team of geneticists and published in a report by the American Journal of Human Genetics and the International Herald Tribune (IHT).

The Alhambra Decree
The findings have a bearing on the question of how many Jews converted to Christianity and how many chose to remain Jewish and be expelled, when King Ferdinand and Queen Isabella signed the Alhambra Decree ordering Jews out of Spain in 1492.

According to Dr. Jonathan Ray, a professor of Jewish studies at Georgetown University, there is a dispute between historians on the debt owed by modern Spanish civilization to Jews and Judaism. Ray says that according to some historians, Spanish civilization is Catholic and other influences are foreign, while other historians see Spain as having been enriched by drawing from all three of its historic cultures: Catholic, Jewish and Muslim.

The study, based on an analysis of Y chromosomes, was conducted by a team of biologists led by Mark Jobling of the University of Leicester in England and Dr. Francesc Calafell of the Pompeu Fabra University in Barcelona. They developed a Y chromosome signature for Sephardic Jewish men by studying Sephardic Jewish communities in places where Jews migrated after being expelled from Spain in 1492. They also characterized the Y chromosomes of the Arab and Berber army that invaded Spain in 711 A.D. from data on people living in Morocco and Western Sahara.

Jews Were City Dwellers
Because most of the Y chromosome remains unchanged from father to son, the proportions of Sephardic and Moorish ancestry detected in the present population are probably the same as those just after the 1492 expulsions. A high proportion of people with Sephardic ancestry was to be expected, Ray told IHT, because "Jews formed a very large part of the urban population up until the great conversions."

Spanish Jewry once constituted one of the largest and most prosperous Jewish communities under Muslim and Christian rule in Spain, before the Jews were expelled in 1492. Today, a few thousand Jews live in Spain, but the descendants of Spanish and Portuguese Jews still make up around a tenth of the global Jewish population.

The term "Sephardic" is often used in a wider sense, however, to include most Jews of Asian and African origin, who use a Sephardic style of liturgy.

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