Early Holocenic and Historic mtDNA African Signatures in the Iberian Peninsula: The Andalusian Region as a Paradigm

Abstract

Determining the timing, identity and direction of migrations in the Mediterranean Basin, the role of “migratory routes” in and among regions of Africa, Europe and Asia, and the effects of sex-specific behaviors of population movements have important implications for our understanding of the present human genetic diversity. A crucial component of the Mediterranean world is its westernmost region. Clear features of transcontinental ancient contacts between North African and Iberian populations surrounding the maritime region of Gibraltar Strait have been identified from archeological data. The attempt to discern origin and dates of migration between close geographically related regions has been a challenge in the field of uniparental-based population genetics. Mitochondrial DNA (mtDNA) studies have been focused on surveying the H1, H3 and V lineages when trying to ascertain north-south migrations, and U6 and L in the opposite direction, assuming that those lineages are good proxies for the ancestry of each side of the Mediterranean. To this end, in the present work we have screened entire mtDNA sequences belonging to U6, M1 and L haplogroups in Andalusians—from Huelva and Granada provinces—and Moroccan Berbers. We present here pioneer data and interpretations on the role of NW Africa and the Iberian Peninsula regarding the time of origin, number of founders and expansion directions of these specific markers. The estimated entrance of the North African U6 lineages into Iberia at 10 ky correlates well with other L African clades, indicating that U6 and some L lineages moved together from Africa to Iberia in the Early Holocene. Still, founder analysis highlights that the high sharing of lineages between North Africa and Iberia results from a complex process continued through time, impairing simplistic interpretations. In particular, our work supports the existence of an ancient, frequently denied, bridge connecting the Maghreb and Andalusia.

Ancient and recent Middle Eastern maternal genetic contribution to North Africa as viewed by mtDNA diversity in Tunisian Arab populations

“…However, the significant presence of Sub‐Saharan lineages (L0, L1, L2, L3, and L4) in the two Tunisian Arab populations (35%) suggests significant admixture with indigenous Berbers, who are known to display Sub‐Saharan contributions since Paleolithic times (Frigi et al, ; Soares et al, ). This includes contributions from the Early Holocene, across the Sahel Belt, during the African Humid Period (Černý et al, ; Hernández et al, ; Podgorná et al, ; Soares et al, ), without excluding a more recent introduction in North Africa through the trans‐Saharan slave routes suggested to be mainly established in the seventh century (Harich et al, ).…”

“…Conversely, the specific North African U6 and M1 haplogroups, particularly in Wesletia (7.81%), may have been brought to North Africa during Paleo‐climatic fluctuations that occurred in North Africa (Secher et al, ) in association with the flourishing of the Iberomaurusian industry (Hernández et al, ; Maca‐Meyer et al, ; Pennarun et al, ; Pereira et al, ) and perhaps later at the Capsian time (Fernandes et al, ; Pennarun et al, ).…”

“…Other studies revealed the arrival of some L sublineages in North Africa across the Sahel Belt during the Early Holocene at the beginning of the African Humid Period (11 000 years ago), particularly L1b and L3e5 which are commonly found in the Lake Chad Basin (Černý, Salas, Hájek, Žaloudková, & Brdička, ; Frigi et al, ; Hernández et al, ; Podgorná, Soares, Pereira, & Černý, ; Soares et al, ). Conversely, U6 and some L sublineages were introduced from northwest Africa into Iberia probably after the Younger Dryas period (Cerezo et al, ; Hernández et al, ; Podgorná et al, ; Secher et al, ; Soares et al, ).…”

“…U6 is more common in western North Africa, whereas M1 is more common in the eastern part (Olivieri et al, ; Pennarun et al, ). The time of the most recent common ancestor (TMRCA) of U6a1, M1a, and M1b of around 20 000 years ago implied their expansion in North Africa in association with the flourishing of the Iberomaurusian industry (Hernández et al, ; Maca‐Meyer et al, ; Pennarun et al, ; Pereira et al, ).…”

“…Through the characterization of key demographic events in Arabia, Fernandes et al () proposed an Epipaleolithic migration around 10 000 years ago of some Eurasian mtDNA sublineages to North Africa, namely HV, K, J1d1a, J2a2b, T2c1, T2b, R0a, X, U5, U5b. Some Sub‐Saharan sublineages, such as L3b1, L3e1, L3e2, and L3e5a, were introduced in North Africa across the Sahel Belt around 8000–6000 years ago (Hernández et al, ; Soares et al, ). North African subhaplogroups U6b, M1b1 (Pennarun et al, ), U6a1a and M1a1 (Fernandes et al, ) appeared later at the Capsian era.…”