From Normandy to Flanders, from southern England to the Netherlands and northern France,
modern people of northwestern Europe form one of the tightest genetic clusters on the continent.
On a PCA plot or with G25-based tools, a French person from Pas-de-Calais can overlap almost
perfectly with someone from Kent, Flanders or Zeeland.
This is not a bug in our calculators. It is the logical result of
the same sequence of population events happening on both sides of the Channel:
Western Hunter-Gatherers, the same Neolithic farmers, the same Bell Beaker expansion, very similar
Iron Age Celtic networks, and then very similar early medieval Germanic migrations.
1. A Shared Mesolithic and Neolithic Foundation
After the Last Glacial Maximum, western Europe was repopulated by a group that geneticists call
Western Hunter-Gatherers (WHG). This WHG ancestry is found from Atlantic France
to Britain and the Low Countries, forming a continuous genetic background. Recent work on the
last hunter-gatherers of Atlantic France (Hoedic, Téviec, etc.) confirms that these coastal
communities were part of the same broader WHG network.9
When farming arrived in Europe from Anatolia, Early European Farmers (EEF)
mixed with WHG populations in similar proportions on both sides of the Channel.
By 3000 BCE, northern France, Belgium, the Netherlands and southern Britain
already shared a remarkably similar WHG + EEF genetic substrate.
2. The Bell Beaker “Reset” of Northwestern Europe
The Bell Beaker Expansion (2600–2000 BCE) introduced Steppe-derived ancestry
across the entire region in a near-simultaneous wave. Britain experienced a population turnover
of up to 90%.1
Bell Beaker groups in France, Belgium and the Low Countries show the same Steppe-rich profile,
with similar Y-DNA lineages (R1b-L151 & R1b-P312), creating a unified genetic block stretching
across the Channel.3, 4
This transformation is the main reason why modern populations from Kent, Flanders,
northern France and the Netherlands overlap almost perfectly in PCA space.
3. Cross-Channel Celtic Worlds in the Iron Age
The Channel was a bridge, not a barrier.
Iron Age Gauls in Normandy closely resemble southern Britons.
Urville-Nacqueville individuals (La Tène) form a genetic contact zone linking both sides.5
A recent Nature study demonstrates substantial continental influence in Iron Age Britain
and pervasive matrilocality—proof of intense mobility between France and southern Britain.6
4. Early Medieval Germanic Migrations
Anglo-Saxons in England and Franks/Saxons/Frisians on the continent came from the same North Sea
populations.7, 8
Individuals from Kent frequently cluster with Early Medieval Frisians and coastal Dutch/German
individuals. The migrations homogenised the region even further.
5. Fine Structure Exists, But the Shared Block Dominates
Modern genetic data show internal French and Belgian structure,10
yet at a continental scale, northern France, Belgium, the Netherlands and southern Britain still
align as one continuum.
6. What This Means for DNA Testers and G25 Users
If your G25 or admixture modelling returns fits that could be British, Dutch, Flemish or northern French,
it is not a limitation of the tool. It reflects the historical reality: these populations are genuinely
close genetically after 5,000 years of parallel population events.
A French person from the far north can score closer to some English regions than to southern France.
Belgians often sit between Dutch and northern French / English.
Why algorithms like G25, ADMIXTURE, qpAdm or PCA have difficulty distinguishing them
Tools such as G25, ADMIXTURE, qpAdm, PCA, D-statistics and similar algorithms
are based on shared allele frequencies across populations.
They do not look at shared DNA segments (IBD) like consumer tests
(AncestryDNA, MyHeritage, 23andMe).
Since Northwestern Europeans descend from the same ancestral layers
(WHG, Neolithic farmers, Bell Beakers, Iron Age Celts, Early Medieval Germanic groups),
they share a very high proportion of the same allele frequencies.
As a result:
- their PCA positions overlap strongly,
- ADMIXTURE components look almost identical,
- G25 modelling often fits multiple NW European sources equally well.
In short, these populations share so many of the same genes that
frequency-based models cannot easily tell them apart.
7. Take-Home Message
Northwestern Europe is a genetic continuum shaped by shared WHG, shared Neolithic ancestry,
the same Bell Beaker transformation, Celtic mobility and parallel Germanic migrations.
Borders changed; the underlying population did not.
