Mesolithic hunter-gatherers split by great genomic divide from Black Sea to Baltic with high east-west differentiation. Western side saw near-total HG replacement by Anatolian farmers during Neolithic. Eastern side maintained pure local HG ancestry without farmer influx until 5000 bp. Yamnaya steppe ancestry formed from 65% Middle Don HGs plus 35% Caucasus HGs. Middle Don HGs carried early Caucasus admixture dated to 8300 bp. Steppe ancestry spread across Europe in 1000 years replacing Neolithic farmers. Corded Ware formed by steppe-Yamnaya mixing exclusively with Globular Amphora farmers. Western HGs derived from southern European sources eastern HGs from Siberian ANE-admixed sources. Scandinavia hit by three distinct HG waves from south Denmark southeast and northwest Russia. Iberian HGs admixed with southeastern European HG ancestry around 8200 bp. Eastern Baltic Ukraine and western Russia HGs persisted unchanged for millennia. Neolithic Denmark farmers carried up to 25% non-local western HG ancestry. Steppe migrations ended great divide flooding east with Yamnaya ancestry. Siberian forest steppe formed Neolithic cline from west Siberian northeast Asian and Paleo-Siberian HGs. Okunevo culture derived from forest steppe HGs plus Afanasievo steppe ancestry around 4600 bp. Post-3700 bp Siberian steppe saw sharp steppe and GAC farmer ancestry influx replacing locals. Ancient groups showed higher genetic differentiation than modern Europeans due to isolation. Yamnaya Y-haplogroups mismatch later Europeans indicating unresolved patrilineal origins.