The phenomenon of distinct genetic substrata in the West, East, and South Slavs would imply several mechanisms, including cultural assimilation of indigenous populations by bearers of Slavic languages as a major mechanism of the spread of Slavic languages to the Balkan Peninsula.[8][9] About 55% of the Bulgarian autosomal genetic legacy is Mediterranean, about the half of which resembles the Caucasian, Middle Eastern and to a lesser extent the North African genetics.[3] Combining all lines of evidence, it is suggested that the major part of the within-Balto-Slavic genetic variation can be mainly attributed to the assimilation of the pre-existing regional genetic components, which differ for West, East and South Slavic-speaking peoples.[8]