Neanderthals have elongated skulls unlike modern humans' globular brains. Modern Europeans carry rare Neanderthal DNA fragments from interbreeding. Neanderthal genes UBR4 and PHLPP1 decrease brain globularity. These genes affect neurogenesis and myelination. Strongest effects occur in putamen and cerebellum. Putamen and cerebellum handle learning, movement, and memory. Differences in globularity exist among modern humans. Large sample of 4500 genomes detected subtle Neanderthal effects. Fossil CT scans confirmed Neanderthal-non-globular endocasts. MRI on thousands measured human brain globularity. Genetic architecture drives evolutionary brain shape changes. Neanderthal introgression influences living human brain structure.