Although the Rh-negative trait is rare in most parts of the world, it occurs in about 15 percent of Caucasians in Europe, Canada, and the United States. The trait’s highest incidence is among the Basques of the Pyrenees (25–35 percent) and the Imazighen (Berbers) of Africa and the Bedouins of the Sinai Peninsula (18–30 percent). Source: Blood: Physiology and Circulation So who are the Bedouins genetically speaking? You may be surprised.