Haplogroup I-P37 (I2a)
I-P37 descends from Europe's Ice Age hunter-gatherers; its Dinaric branch is today the most common paternal line in the western Balkans. Explore the branch in the full Y-DNA haplotree: sub-branches, defining variants and where its testers live. Free, no account needed.
Paternal branch
Live tester counts
Free · no account needed
Paternal line
I-P37
- Testers
- 16,778
- 1,263 on this exact branch
- Strongest today
- Bosnia and Herzegovina, Croatia, Serbia
- Formed
- Oldest man on this line
Origin and distribution of I-P37 (I2a)
What is I-P37? It is the largest surviving branch of I2a, descended from Europe's Mesolithic hunter-gatherers, whose young Dinaric sub-branch is today the most common paternal line in the western Balkans.
- Its deep root
- I2 lineages are found throughout Europe's Mesolithic hunter-gatherers, and P37 sublineages persisted through the Neolithic from Sardinia to the Atlantic.Source: The genomic history of southeastern Europe (2018)
- The Dinaric expansion
- The I-L621 and CTS10228 cluster multiplied during the first millennium CE, riding the early medieval Slavic migrations: a young expansion on a very old lineage.Source: A genetic history of the Balkans from Roman frontier to Slavic migrations (2023)
- Where it is common
- Peaks in Bosnia and Herzegovina, Croatia, Montenegro and Serbia, with a second wing widespread across the Slavic-speaking east.
I-P37 is the largest surviving branch of haplogroup I2, a lineage whose roots in Europe run deeper than farming itself. Ancient DNA finds I2 lines throughout the continent's Mesolithic hunter-gatherers, and P37 sublineages persisted through the Neolithic in pockets from Sardinia to the Atlantic façade.
The branch's modern story is dominated by one spectacular late expansion: the so-called Dinaric cluster (I-L621 > I-CTS10228), which multiplied during the first millennium CE and today makes I-P37 the most common paternal haplogroup in the western Balkans, peaking in Bosnia and Herzegovina, Croatia, Montenegro and Serbia, with a second wing widespread across the Slavic-speaking east. Its distribution tracks the early medieval Slavic migrations, a young expansion riding a very old lineage.
One line among many: your Y haplogroup traces a single paternal line, one ancestor per generation out of thousands, so it is a thread of deep ancestry, not an ethnicity and not a percentage of who you are. Two men in the same branch share a forefather, but the rest of their genomes can differ as much as any two strangers'.
The line through time
Each branch on this line from the root of the tree, oldest first.
Where testers are found
Counts of people who took a Y-DNA test and shared an origin. They describe the tested world, not ancient frequencies.
England
554 · 14%
Ireland
518 · 13%
Ukraine
514 · 13%
United States
467 · 12%
Poland
417 · 11%
Germany
337 · 8.6%
Russian Federation
333 · 8.5%
Scotland
248 · 6.4%
Plus 10,704 testers who gave no country. Shares are of testers with a known country.
Where this branch runs strongest
The share of each country's testers who sit on this branch.
Bosnia and Herzegovina
1 in 3 · 36%
Croatia
1 in 3 · 30%
Serbia
1 in 4 · 25%
What defines it
The changes on the Y chromosome that every man on this branch carries. Positions are on the GRCh38 reference.
Is this your line?
If you have tested with a consumer DNA company, your own branch is already in your raw data file. The free Clade Finder reads it and shows you where you sit on this tree.
Find my branch, freePrefer it read for you? The Ancient Ancestry report can carry your paternal haplogroup as an add-on, placed on this same tree beside your ancestry model.
Frequently asked questions
What is haplogroup I-P37 (I2a)?
I-P37 descends from Europe's Ice Age hunter-gatherers; its Dinaric branch is today the most common paternal line in the western Balkans. It is a branch of the Y-DNA tree: everyone in it inherits the same set of defining mutations from one shared forefather.
How do I find out if I belong to I-P37 (I2a)?
If you have already tested with a consumer DNA company, the free Y-DNA Clade Finder reads a raw DNA export (23andMe, AncestryDNA, MyHeritage or a VCF) and places you on the tree at the resolution your file supports. It is free, and the file is discarded after analysis. A dedicated Y-DNA sequencing test resolves deeper branches than a genotyping chip can.
Does belonging to I-P37 (I2a) make me descend from one people?
No. A haplogroup follows a single paternal line, one ancestor per generation, while the rest of your ancestry doubles every generation back. It is a deep-time thread, not an ethnicity, and two members of the same branch can otherwise be as genetically different as any two strangers.
What does this page's tree data show?
The branch view on this page shows the branch inside the full Y-DNA haplotree of tested lineages: the line it descends from, the branches below it, the variants that define it, and the countries its testers report. Counts reflect people who have taken a Y-DNA test and shared an origin, so they describe the tested world, not ancient frequencies.
Keep exploring
Don't know your haplogroup yet? The free Y-DNA Clade Finder reads it from a raw DNA export. Or browse the whole tree in the Y-DNA Haplotree. Other major branches: