Back when our species was just arriving in Europe and Asia from Africa, there were already two groups of archaic hominins (that’s us and our extinct ancestors) living there: the well-studied Neanderthals of Europe and parts of Asia and the mysterious Denisovans known only from a cave in southern Siberia.
In the mid-1990s, thousands of bones and teeth were discovered in a cave called Sima de los Huesos, or “pit of bones,” in the Atapuerca Mountains of northern Spain. A few of the fossils, dating back around 430,000 years, looked a lot like primitive Neanderthals. Some researchers think they belonged to Homo heidelbergensis, a species thought to have given rise to both Neanderthals and humans; others think they belonged to members of the Denisovans based on mitochondrial DNA from one of the Sima fossil thighbones (called femur XIII). However, mitochondrial DNA only represents a fraction of the genome and, as it is inherited only from the mother, doesn’t reflect a population’s complete evolutionary history.
Now, Matthias Meyer of the Max Planck Institute for Evolutionary Anthropology and colleagues have sequenced nuclear DNA extracted from multiple Sima specimens – the oldest nuclear DNA ever sequenced from a member of the human family, Science reports. Their findings place individuals from the pit firmly on the Neanderthal evolutionary lineage. The work was presented at the European Society for the study of Human Evolution meeting in London this week.
The team isolated DNA from four Sima specimens: another femur fragment, an incisor, a molar and a scapula (or shoulder blade). They didn’t recover any meaningful genetic data from the scapula, but they did manage to obtain up to three million bases of DNA sequences form the other three.
When they scanned this DNA for markers found only in Neanderthals, Denisovans or modern humans, they found that the nuclear genomes of those specimens were significantly more similar to Neanderthals. “Indeed, the Sima de los Huesos specimens are early Neanderthals or related to early Neanderthals,” Meyer said at the meeting, according to Science. And that suggests the Neanderthal-Denisovan split happened before 430,000 years ago.