It used to be thought that, as a tree took root, budded, branched and died, humanity predictably grew, spread and thrived, with few false starts or dead ends. The discovery of our archaic relatives, the Neanderthals and Denisovans, put an end to that thinking. Once science possessed whole genomes, statistical comparisons suggested not only that there were other archaic skeletons still waiting to be found, but many extinct populations and dead branches. “Ghost populations” are peoples dimly glimpsed in ancient DNA data who do not survive as a coherent population today. The prototype was Mal’ta Boy, who was predicted before he was discovered. His Siberian gene pool from 24,000 years ago (with U2 as his mitochondrial haplotype and R1b as his male lineage) is undoubtedly the source of Ancient North Eurasians, the European founder group responsible for the blond hair mutation. An eastern branch mixed with East Asians and produced Native Americans. This is one reason modern-day Finns and Native Americans have genetic similarities. But Mal’ta Boy’s DNA died out in Siberia. Today’s Siberians have none of it in their ancestry. It is a ghost population.