Overview
I1d represents a set of northern and northwestern European branches within haplogroup I1 that are distinct from the major I1a (L22), I1b (Z58) and I1c (Z63) radiations. It likely emerged in the same late Neolithic to early Bronze Age period that saw the wider I1 expansion in Scandinavia and the North Sea region, but its later demographic trajectory is characterized by smaller and more regionally focused founder events. I1d is less frequent than I1a or I1b and tends to appear in populations with complex mixtures of Scandinavian, North Sea and British Isles ancestry.
Genetically, I1d contains several microbranches that have been detected through high coverage sequencing projects. These lineages show signs of moderate expansion but did not reach the very high frequencies observed in core I1a Scandinavian clusters. Their distribution suggests involvement in early movements across the North Sea and into the British Isles, as well as participation in later medieval demographic processes in northern and western Europe.
Geographic distribution
Modern I1d lineages are found at low to moderate frequencies in the British Isles, northern France, the Low Countries, Denmark and coastal Germany. They also occur in Norway and Sweden, particularly in regions with historical connections to North Sea trade and migration routes. In England and Scotland, I1d often appears in areas with documented Viking Age and later North Sea contacts but does not dominate the paternal landscape.
Outside this core zone, I1d is detected at low levels across central Europe and in European descendant populations overseas. Its presence in eastern Europe and the Balkans is rare and primarily reflects more recent historical movements rather than deep regional roots.
Ancient DNA
- Some early medieval burials in the British Isles and the Low Countries carry I1 lineages that could belong to I1d or its immediate upstream structure, although many ancient samples are not yet resolved at this level.
- Viking Age contexts with strong North Sea orientation occasionally show I1 lineages phylogenetically close to I1d clusters.
- Later medieval remains from coastal North Sea regions display I1 diversity that includes branches plausibly connected to I1d.
Phylogeny & subclades
Within I1, I1d sits as a smaller sister cluster to the more expansive I1a, I1b and I1c branches. The defining Z2041 and related markers identify a set of lineages that diverged during the main I1 star like expansion but did not undergo the same scale of growth. Internal structure includes several shallow subbranches that correspond to regional founder events in the British Isles and the North Sea coast.
In the atlas, I1d provides a container for those northern European I1 lineages that have clear regional signal but do not belong to the main L22 based Scandinavian or Z58 and Z63 based continental and eastern clusters.
- I1d* basal northern European lineages
- I1d1 – British Isles oriented clusters
- I1d2 – North Sea coastal microbranches
Notes & context
Including I1d as a separate branch prevents the internal structure of I1 from being over simplified and allows users to see that not all northern European I1 diversity is captured by the three largest radiations. I1d is important for detailed reconstructions of North Sea and British Isles paternal histories.
References & external links