African mtDNA in the Iberian Northern plateau

Alvarez et al. Mitochondrial DNA patterns in the Iberian Northern plateau: Population dynamics and substructure of the Zamora province. American Journal of Physical Anthropology. Early View. Published Online: 1 Feb 2010. 10.1002/ar.20976

In the province of Zamora, if the total number of African lineages are taken into account (Hgs L1b, L2b, L3, M1, and U6a1a), the contribution represents 5.7% of the total Hg composition. [. . .] As regards sub-Saharan Hgs (L1b, L2b, and L3b), the high frequency found in the southern regions of Zamora, 18.2% in Sayago and 8.1% in Bajo Duero, is comparable to that described for the South of Portugal, but it does not have any parallels with any other analyzed areas in the Northern part of Iberia (Pereira et al., 2005).

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In Zamora, both North African and sub- Saharan mtDNA lineages were found. It has been suggested that U6 and M1 Hgs, detected in low frequencies in Zamora, have been involved in the dispersal of Upper Palaeolithic Levantine people to North Africa along the south Mediterranean coastal areas (Olivieri et al., 2006). In this scenario, prehistoric links between North Africa and Iberia could explain the presence of this Hg in the Northern part of Iberia. The identification of a M1 mtDNA African lineage in a Basque necropolis dating back to the 6th–7th centuries (Izagirre et al., 2005) together with cattle from the Bronze Age (Anderung et al., 2005) with mtDNA African lineage support this hypothesis. However, paying heed to the low diversity of these Hg in Iberia, a more recent North African contribution that claims that it may be due to the flexible procreation between Christians and Muslims (females) (Pereira et al., 2005) is plausible. Another explanation is the relocation of moriscos, a hypothesis recently proposed by Adams et al. (2008) based on Y chromosome data and supported by historical data available for the studied region (Martin, 2003).

As regards sub-Saharan lineages, it is well known that during the 16th–19th centuries, African slaves were captured along the West African Coast and were frequently transported to Cape Verde (Macaronesia region). This archipelago served, from the beginning of the slave trade, as a kind of platform that connected the African continent to Europe, America, and India from which slaves were transported to different regions, including the other Macaronesia archipelagos (Canary, Madeira, and Azores) and mainland Portugal (Comissa˜o Nacional para as Comemorac¸o˜es dos Descobrimentos Portugueses, 1999). Thus, paying heed to the sharing Ht analyses, it seems that the slave trade, during the 16th–19th centuries, better explains the African sub-Saharan lineages found in the Iberian Peninsula (including those found in the Zamora province). However, in contrast to the welldocumented presence of slaves in the Portuguese territories (Comissa˜o Nacional para as Comemorac¸o˜es dos Descobrimentos Portugueses, 1999), the same evidence does not exist for mainland Spain. In the Zamora province, there is only one reference to the presence of slaves in the province (Carbajo Martin, 1995). As the Hts found in the area are also shared with North African populations, we cannot discard the possibility that these lineages derived from the North African Muslim permanence in the Iberian Peninsula. A great number of Berber troops relocated their family groups to the gained territories (Salvatierra and Canto, 2008). Thus, this phenomenon could explain the presence of sub-Saharan lineages.