By Katie Hunt, CNN
(CNN) — Human evolution’s biggest mystery, which emerged 15 years ago from a 60,000-year-old pinkie finger bone, finally started to unravel in 2025.
Analysis of DNA extracted from the fossil electrified the scientific community in 2010, when it revealed a previously unknown human population that had, in the distant past, encountered and interbred with our own species, Homo sapiens. This enigmatic group became known as the Denisovans after Denisova Cave in Siberia’s Altai Mountains, where the pinkie finger was found.
Despite intimate knowledge of this population’s genetic makeup, traces of which millions of people carry today, scientists knew nothing about the appearance of the Denisovans, or where they lived or why they disappeared. The discovery, and the questions it unleashed, galvanized a generation of geneticists, archaeologists and paleoanthropologists.
Some of that work paid off this year, and scientists at last put a face to the Denisovan name by extracting new clues from another well-known fossil: a prehistoric human skull that didn’t seem to fit with any known group. Now, other jigsaw pieces have begun to fall into place.
Enter ‘Dragon Man’
When the skull came to light in Harbin in northeastern China in 2018 after being stashed for safekeeping at the bottom of a well for decades, some scientists had a hunch that it might be Denisovan.
DNA sequences from the group had been detected in the genomes of present-day Asians, but not Europeans, suggesting that this region was where the Denisovans predominantly lived.
Based on its distinctive shape, the researchers attributed the skull to a newfound species they called Homo longi or “Dragon Man.” The dozen or so Denisovan fossils that had been identified since 2010 using DNA were too small and fragmentary to warrant an official species name.
Getting ancient DNA from the skull, which was estimated to be 146,000 years old, was the key to understanding whether there was a link between Dragon Man and the Denisovans. However, it proved to be tricky.
A team led by Qiaomei Fu, a geneticist and professor at the Institute of Vertebrate Paleontology and Paleoanthropology, part of the Chinese Academy of Sciences in Beijing, tested six bone samples from Dragon Man’s lone surviving tooth and the cranium’s petrous bone, a dense piece at the base of the skull that’s often a rich source of DNA in fossils. However, the samples yielded no results.
But Fu, who as a young researcher had been part of the team at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, that first discovered the Denisovans, reported in June that her team had been able to retrieve Denisovan genetic material from an unexpected source: Dragon Man’s dental calculus — the gunk left on teeth that can over time form a hard layer and preserve DNA from the mouth.
That information wasn’t a slam-dunk result. The genetic material researchers had retrieved was mitochondrial DNA, which, unlike nuclear DNA, is only inherited through the maternal line, providing an incomplete picture of an individual’s genomic ancestry. This finding meant, potentially, that Dragon Man could have been a mix of two species, something that’s not unprecedented. In 2018, scientists revealed a fossilized bone from Denisova Cave that belonged to a girl with Read more