A fragment of bone about the size of a large coin told one of the most specific stories ever extracted from the deep past. It was identified not by what it looked like—it looked like nothing in particular, a splinter among thousands—but by the proteins locked inside it, and then by the DNA those proteins had protected for roughly 90,000 years. When scientists read that DNA in full, they found something no one had ever found before: an individual whose mother belonged to one ancient human group and whose father belonged to another. A first-generation child of two populations that had diverged hundreds of thousands of years earlier and then, once, come together.
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## A Fragment Among Thousands
The bone arrived in a sample collection without a biography. At Denisova Cave in the Altai Mountains of southern Siberia, archaeological excavation produces thousands of small bone fragments per season—fragments from the teeth and limbs and skulls of the animals that sheltered in the cave, were dragged there by predators, or died there across hundreds of thousands of years of accumulated time. Most of these fragments are unidentifiable by shape. They are too small, too broken, too stripped of the features that would let a trained anatomist say what animal produced them, let alone which part of that animal.
Denisova Cave’s excavation teams collected and catalogued these fragments systematically. By the time researchers began sorting through a particular batch in 2015, the archive held more than two thousand unidentified pieces from the cave’s East Gallery alone. The fragment eventually catalogued as Denisova 11 was among them. It was found in 2012, in layer 12 of the East Gallery. Before analysis, it weighed 1.68 grams and measured approximately 24.7 millimeters by 8.39 millimeters—smaller than a thumb’s width.