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Early Migrations to Canary Islands Untangled with Ancient Mitochondrial DNA

NEW YORK (GenomeWeb) – Using ancient mitochondrial genome sequences, a team from the US, Spain, and the UK has proposed a model for the peopling of the Canary Islands that includes multiple migrations, mainly from North Africa.

Researchers from Stanford University, the University of La Laguna, and elsewhere sequenced four dozen mitochondrial genomes stretching back hundreds of years from sites on seven Canary Islands. With phylogeographic analyses and comparisons to present-day populations, they identified several mitochondrial lineages that appear to be specific to the Canary Islands and saw variable levels of Central North African, West African, and Near Eastern ancestry from one island to the next.

"These results point to a complex scenario, where different migration waves from a dynamic and evolving North African population reached the islands over time," corresponding and co-first author Rosa Fregel and her colleagues wrote in their PLOS One study. "Every island experienced their own evolutionary path, determined by the environmental conditions and limitations of insularity."

Fregel is currently a biochemistry, microbiology, cell biology, and genetics researcher at the University of La Laguna. She was previously a postdoc in senior author Carlos Bustamante's genetics lab at Stanford.

Though genetic studies on current Canary Island populations indicate that North African populations served as a source for indigenous ancestry on the islands, the team noted, European colonization in the 15th century and other historical events introduced new populations to the islands. Moreover, the authors explained, there have also been hints that "indigenous populations from different islands might have experienced different demographic processes."

Consequently, they set out to profile genetic features from ancient indigenous individuals spanning all seven islands in an effort to accurately characterize the archipelago's indigenous population.

Using whole-genome, in-solution capture-enrichment, and short-read sequencing, the researchers generated full mitochondrial genome sequences, covered to an average depth of 140-fold, for ancient samples from 25 sampling sites on Lanzarote, Fuerteventura, Gran Canaria, Tenerife, La Gomera, La Palma, and El Hierro that stretched over an estimated 1,200 years. They also considered mitochondrial genomes for 18 present-day individuals from the Canary Islands, along with new and previously hypervariable region mitochondrial profiles for indigenous Canarians.

Based on the ancestral contributions they detected in populations from each island in the context of the islands' distance from the mainland, the team proposed a peopling model for the Canary Islands that involved at least two early migration events. The available data also pointed to mixing between North African Berbers and populations from the Mediterranean prior to Canary Island colonization, consistent with previously proposed interactions between populations during Neolithic migrations from the Middle East to Europe and Africa.

"The presence of haplogroups of Mediterranean distribution in the indigenous people of the Canaries demonstrates the impact of these prehistoric and historical migrations in the Berbers and that they were already an admixed population at the time of the indigenous colonization of the islands," the authors reported.

Although the current findings provide a more nuanced view of indigenous populations on the Canary Islands than was previously available, they noted that future studies that include larger ancient mtDNA sets, genome-wide data, archeological information, and radiocarbon dating clues "will be essential for improving our knowledge of the origins and evolution of the indigenous population of the Canary Islands."