BA Orkney genomes cluster with northern European Bell Beaker and BA samples, distinct from Neolithic Orkney. Orkney BA has 55% Steppe, 33% Anatolian Neolithic Farmer, 12% Western Hunter-Gatherer ancestry. LoN BA derives 93-96% ancestry from Scottish BBC and 4-7% local Neolithic. mtDNA lineages in BA LoN mostly arrived with BBC or Corded Ware from continent. Neolithic Orkney Y-DNA all I2a – BA LoN Y-DNA nine of ten I2a1b-M423 from local Neolithic. I2a1b-M423 absent in European BBC/BA except Orkney persistence. BA LoN effective population size around 400, indicating small endogamous group. Multiple burial shows siblings sharing rare H39 mtDNA and common I2a1b Y-DNA. Autosomal and mtDNA replacement achieved via local men marrying immigrant women over five generations. IA Orkney shifts to R1b-M269 Y-DNA like mainland. Neolithic Orkney mtDNA European Neolithic type, lacking Steppe CHG signal. U5b2a3b mtDNA potential continuity from Neolithic or Mesolithic Orkney to modern. I2a1b-M423 originated in Atlantic facade Neolithic, possibly from assimilated hunter-gatherers. No evidence of close kinship beyond one sibling pair in LoN. Modern Orcadians have higher CHG from Norse admixture. Orkney BA lost Beaker culture despite BBC genetic source. LoN samples form tight genetic clade, unlike diverse Neolithic.