In 2010, an international team of scientists announced a remarkable discovery from Denisova Cave in Siberia. A tiny fragment of a finger bone revealed DNA that was distinct from modern humans and from ancient Neandertal DNA. Further research revealed a handful of other fossils, mostly just teeth. The genome of these “Denisovans” matched sequences found mostly in the south Pacific, especially among the indigenous tribes of Papua New Guinea. With so few (and such tiny) fossils available to researchers, no one knew what the Denisovans actually looked like. In a sense, they were a genome in search of a form.
In this week’s issue of Nature, another international research team announced what many have long awaited: a large Denisovan fossil. This fossil – the right side of a jawbone with two molar teeth – was originally discovered in 1980 in Baishiya Karst Cave in Xiahe, China on the east end of the Tibetan plateau. Researchers recently examined the fossil for both DNA and proteins. They found no DNA, but the proteins proved to match most closely the protein sequences from the Denisovans. This Xiahe mandible is the first confirmed Denisovan fossil found outside of Denisova Cave.
Even though it isn’t a very big fossil, it still tells us much more about their appearance than anything discovered at Denisova. Like most fossil humans, they lack a chin, but they also had extremely large molars, larger than any other hominin in the fossil record. They also lacked wisdom teeth. The shape of the mandible closely matches known mandibles from Asian Homo erectus, which suggests that there may be other Denisovan fossils already sitting in museums waiting to be discovered.
Even as we puzzle over these fascinating fossils, the living descendants of these people remind us that they were fully human, made in the image of God. As we learn more and more about fossil humans, we continue to realize how much we don’t know. Less than a decade ago, we had no idea that Denisovans even existed, and even now, we have only the slightest idea of what they looked like.
What will we discover tomorrow?
Chen et al. 2019. A late Middle Pleistocene Denisovan mandible from the Tibetan Plateau. Nature 10.1038/s41586-019-1139-x.