Explaining close relatedness and the founding of the Faroe Islands from a bottleneck effect observed in ROHs: Topic: 19. Population Genetics and Evolutionary Genetics

Background/Objectives: The population of the Faroe Islands, about 50,000 people, is an
isolated community with a high incidence of rare diseases, e.g., Primary Carnitine Deficiency
(1:300). For diagnostic purposes, some cases not affected by known mutations were wholegenome sequenced at high coverage (x37). Here, the genomes from consenting individuals are utilized to explore the genomic variation and the ancestral history of the population.

Methods: We determine the number of SNPs and heterozygosity for eight individual and
merged samples. We study the pairwise relatedness through kinship, inbreeding from runs of
homozygosity (ROHs), and analyse the minor allele frequency distribution. Additionally, the
population ancestry and the timing of the founding event are estimated.

Results: Close relatedness was found between all the supposedly unrelated individuals.
From ROHs, the high relatedness is interpreted as an ancient property of the isolated
population. A bottleneck effect is estimated, starting between years 50 and 300 AD, with a
maximum effect in the year 600 AD. A distinct clustering near the central European and
British populations of the 1000 Genome Project is likely the result of the population isolation
and genetic drift. The minor allele frequency distribution suggests many rare variants.

Conclusion: The ancestry is European, while inbreeding is higher compared to
contemporary European populations and population isolates. The Faroese population
exhibits inbreeding like ancient Europeans. We discovered a bottlenecked and
consanguineous population event starting in the 1st-4th century, potentially 2-3 centuries
earlier than previously believed based on archaeological findings.