P21.021.C The first settlers of the Faroe Islands - impacts on modern heterozygosity and personalized medicine: Abstracts from the 58th European Society of Human Genetics (ESHG) Conference: Hybrid Posters. Eur J Hum Genet 33 (Suppl 1), 508–1220 (2025). https://doi.org/10.1038/s41431-025-01935-5

Background: The Faroe Islands, an isolated population of ~50,000
people, exhibit a high incidence of rare diseases, such as Primary
Carnitine Deficiency (1:300). For diagnostic purposes, whole
genomes from cases not affected by known mutations were
sequenced at high coverage (x37). We explore the genomic
variation and study the arrival and ancestry of the founding
population.
   Methods: We examined the relationship between the number
(NROH) and sum (SROH) of ROHs to discover a bottleneck effect
for ROHs larger than a minimum length. From this length and
theory for the length distribution of ROHs, we estimate the timing
of the initial settlement. Whole-genome SNPs and multidimensional scaling (MDS) were used to assess ancestry. SNPs within
ROHs of different length intervals provided further insights into
settlement timing and origins.
   Results: Heterozygosity was 0.60, 0.29 and 0.93 for all, shared
and unique SNPs, respectively. A population bottleneck is
estimated to have begun between 50 and 300 AD, peaking
around 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. Further analysis
using reference data including more populations from the British
Isles and Scandinavia suggests the founders were Orcadians, or
settlers of both Scandinavian and British ancestry.
Conclusion: The Faroese population is of European origin,
possibly Orcadian or mixed central European/British/Scandinavian
ancestry. This study suggests the population was founded in the
1st-4th century, potentially 2–3 centuries earlier than previously
believed based on archaeological findings.
C.O.I. Disclosure:
H. Gislason: None