After an intensive bibliographic search, we compiled all the available data on allele frequencies for classical genetic polymorphisms referring to North African populations and synthesized the data in an attempt to reconstruct the populations' demographic history using two complementary methods: (1) principal components analysis and (2) genetic distances represented by neighbor-joining trees. In both analyses the main feature of the genetic landscape in northern Africa is an east-west pattern of variation pointing to the differentiation between the Berber and Arab population groups of the northwest and the populations of Libya and Egypt. Moreover, Libya and Egypt show the smallest genetic distances with the European populations, including the Iberian Peninsula. The most plausible interpretation of these results is that, although demic diffusion during the Neolithic could explain the genetic similarity between northeast Africa and Europe by a parallel process of gene flow from the Near East, a Mesolithic (or older) differentiation of the populations in the northwestern regions with later limited gene flow is needed to understand the genetic picture. The most isolated groups (Mauritanians, Tuaregs, and south Algerian Berbers) were the most differentiated and, although no clear structure can be discerned among the different Arab- and Berber-speaking groups, Arab speakers as a whole are closer to Egyptians and Libyans. By contrast, the genetic contribution of sub-Saharan Africa appears to be small.
PIP: An extensive bibliographic search was conducted to compile all available data on allele frequencies for classical genetic polymorphisms referring to North African populations. The data were then synthesized to reconstruct the population's demographic history using principal components analysis and genetic distances represented by neighbor-joining trees. Both analyses identified an east-west pattern of genetic variation in northern Africa pointing to the differentiation between the Berber and Arab population groups of the northwest and the populations of Libya and Egypt. Libya and Egypt are also the smallest genetic distances away from European populations. Demic diffusion during the Neolithic period could explain the genetic similarity between northeast Africa and Europe through a parallel process of gene flow from the Near East, but a Mesolithic or older differentiation of the populations into the northwestern regions with later limited gene flow is needed to understand this genetic picture. Mauritanians, Tuaregs, and south Algerian Berbers, the most isolated groups, were the most differentiated, while Arab speakers overall are closer to Egyptians and Libyans. The genetic contribution of sub-Saharan Africa appears to be small.