Genetic heterogeneity of Berber peoples as a result of differential migration and admixture patterns

Abstract

The genome-wide structure of North African populations has been describe d as an amalgam of autochthonous, Middle Eastern, European and Sub-Saharan ancestries. The indigenous North African genetic ancestry has been estimated to be derived from a "back to Africa" migration dated in pre-Holocean times, and suggested to be in high est frequency in Berber populations, which are considered the autochthonous populations of North Africa.

The lack of genetic knowledge on Berber populations in the current datasets prevents the understanding of the complex population processes occurred in North Africa. We have genotyped ~900,000 genome-wide SNPs in four different Berber groups and compared the results with other North African and neighboring groups. Our research reflects the complex structure of North African populations due to multiple admixture processes. Berber groups are very heterogeneous, showing different patterns of admixture and demographic histories, such as relevant endogamy levels within groups. The analysis of haplotype structure and the ancestral relationship between individuals has allowed us to estimate historical dates for some migrations coming from the Middle East and Sub-Saharan Africa into North Africa, affecting in an heterogeneous way the populations of the region. In addition, the comparison of autosomal and sexual chromosomes has shown a sexual bias in the admixture between North African populations and their surrounding neighbors, being the North African autochthonous component mainly derived from males and the European admixture driven by women. This study brings light to the origin of Berbers and the complex admixture processes in the population of North Africa.