Pääbo moved to the Max Planck Institute for Evolutionary Anthropology in Leipzig in 1997 and built a team around these emerging technologies. The facility was designed from the start for ancient DNA work: positive-pressure clean rooms, ultraviolet decontamination of surfaces, researchers who had their own genomes sequenced so their contamination could be identified and excluded. The Neanderthal genome sequencing project, which ultimately produced the first draft Neanderthal genome published in 2010, was the flagship achievement of this program. The Denisovan discovery came in the same publication—a serendipitous consequence of applying the same sequencing to a finger bone from a site already under investigation.
By the time Viviane Slon was sequencing the Denisova 11 nuclear genome in 2017 and 2018, the methods had been refined through a decade of application to samples from across Eurasia. The extraction protocols had been improved to maximize recovery of ancient DNA. The bioinformatic methods for handling low-coverage, damaged ancient genomes had been developed and tested on many samples. The statistical frameworks for inferring population ancestry from ancient genomes had been validated against results obtained independently through other methods.
This context matters because it explains why the Denisova 11 finding could be trusted. The researchers were not working at the edge of what was technically possible; they were applying well-validated methods to a new sample. The unusual composition of the genome—roughly half Neanderthal, half Denisovan—was startling, but the methods for identifying such a composition were by this point standard.
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## Denisova Cave’s Place in the Scientific Record