In 2010, DNA was extracted from a tiny piece of a young girl's finger-bone in Denisova Cave in Siberia's Altai Mountains. The sequence showed she was neither Neanderthal nor modern human, but belonged to a previously unknown human species. The physical record is sparse — a few teeth, a jaw fragment, bone splinters — but the genome is rich. Denisovans are the first human species defined through DNA rather than anatomy.

The genome showed that all three humans interbred. Modern Melanesians, Aboriginal Australians, and parts of East and Southeast Asian populations carry around 3–6% Denisovan ancestry in their genomes. The high-altitude adaptation of Tibetans rests on an EPAS1 gene variant inherited from Denisovans and selected for in their environment — a concrete, functional legacy of that introgression.

In 2019 a mandible from Baishiya Cave on the Tibetan Plateau, thousands of kilometres from the Altai, was identified as Denisovan. The species lived across a wide Asian range, from high mountains to tropical islands. Denisovans disappear from the record around 30,000 years ago — yet their DNA still lives in the cells of millions of people today.