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I2-M284
I2a2a1 (M284) is a distinctively insular branch of haplogroup I2 with deep roots in prehistoric Britain. It is widely considered one of the signature lineages of pre-Indo-European Neolithic and Chalcolithic populations in the British Isles. Its demographic trajectory differs sharply from continental I2 branches: instead of massive expansions, M284 maintained a stable but localized presence, later integrating into Bronze Age and Iron Age cultural contexts.
Modern distributions show highest frequencies in England, Wales, and parts of Ireland and Scotland. The lineage is strongly associated with ancient British substrate populations and appears only sparsely in continental Europe, reflecting limited back-migration.
I2a2a1 forms a key insular offshoot of the broader I2a2 (M223) radiation. M284 diverged early from continental European branches, forming a British-specific clade characterized by markers such as L1195 and Y3723. Its internal structure includes several micro-branches that map well to regional patterns across England and Wales.
Because I2-M284 is strongly insular and archaeogenetically well-represented, it is widely used to trace the genetic prehistory of Britain prior to the major Bronze Age steppe migrations.