E-M81 is the most common subclade of E-L19/V257 and found in the Maghreb, dominated by its sub-clade E-M183. This haplogroup reaches a mean frequency of 42% in North Africa, decreasing in frequency from 100% in some isolated Berber populations to approximately 10% to the east of this range in Egypt.[10][11][12] Because of its prevalence among these groups and also others such as Mozabite, Middle Atlas, Kabyle and other Berber groups, it is sometimes referred to as a genetic "Berber marker". Pereira et al.