For more than thirty years, the face looking out from museum displays and documentary films was the same: a lean, weathered man in his middle years, with a full head of dark hair, light skin, and the rugged look of someone who had spent his life walking the high passes of the Alps.
That image came from the best available science of the early 2010s. It had been built from the first ancient mummy genome ever sequenced, from physical reconstruction based on computed tomography scans of the actual skull, and from decades of forensic and anthropological work on what remained of the man himself.
Then a team of scientists sequenced his genome again.
Using newer technology, cleaner samples, and a comparison dataset containing thousands of ancient European individuals rather than the handful available in 2012, the researchers produced a higher-quality read of the same DNA — and found that the previous picture had been built on a foundation with an invisible crack. Contamination from modern human DNA had crept into the original analysis, and that contamination had quietly distorted several of the most cited findings. When the contamination was removed and the analysis was redone, a different person emerged: darker skin, a predisposition to baldness that explained why the mummy itself was found essentially hairless, and an ancestry so purely rooted in the first farmers who had crossed from Anatolia into Europe that he stood apart from every other contemporaneous individual in the genomic record.
The familiar reconstructions, it turned out, had been telling a story that the DNA did not quite support.