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Y-DNA Haplogroup Atlas

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Haplogroup I1i

I1-BY158

Macro-haplogroup
I
Parent clade
I1
Formed (estimate)
c. 3,500–4,000 years before present
TMRCA (estimate)
c. 2,400–2,700 years ago

Overview

I1i (BY158) represents a transitional coastal lineage connecting the late Nordic Bronze Age sphere of southern Scandinavia with the maritime interaction corridors of the Baltic and North Sea. This clade formed within a period characterized by increased long-distance mobility, the emergence of specialized seafaring groups, and intensified cultural exchanges across Denmark, southern Norway, Jutland, Frisia and the western Baltic. Unlike major I1 clusters that experienced substantial demographic expansions, I1i retained moderate but stable growth, marking it as a lineage tied to localized but well-connected maritime populations.

Geographic distribution

Present-day occurrences of I1i are concentrated along the North Sea and Baltic coasts, particularly in Denmark, northern Germany, the Netherlands, Norway and southern Sweden. Its appearance in England and Scotland corresponds primarily to Anglo-Saxon and later Viking migrations. Minor frequencies in Poland, Latvia and Estonia reflect the clade’s Baltic engagement during the Iron Age.

Ancient DNA

  • Iron Age individuals from Jutland and Schleswig-Holstein show upstream relationships to BY158-related lineages.
  • Viking Age burials from Denmark and coastal Norway include samples belonging to Z58 > Z138 > BY158 frameworks.
  • North Sea medieval skeletal remains, including Frisian and Saxon contexts, show genetic proximity to I1i microclades.

Phylogeny & subclades

I1i descends from the broader Z58 > Z138 coastal radiation but branches separately from major clusters such as Z63 and Z2041. BY158 and companion markers Y7075 and BY160 define its phylogenetic core. Internal diversification is modest, with downstream microclades showing geography-driven structuring around the Jutland–Frisia–Skagerrak triangle.

  • I1-Y7075
  • I1-BY160
  • I1-Y7073
  • Basal BY158* clades

Notes & context

I1i is a particularly informative lineage for reconstructing maritime cultural zones of the Late Bronze and Iron Age. Its presence at the junction of multiple coastal regions highlights its role in shaping early Germanic and proto-Scandinavian demographic networks.