Fossil tooth pushes back record of mysterious Neandertal relative

DNA retrieved from a child’s worn-down fossil tooth shows the ancient Asian roots of extinct Neandertal relatives called Denisovans, researchers say.

A 10- to 12-year-old female Denisovan, represented by the tooth, lived at least 100,000 years ago, conclude evolutionary geneticist Viviane Slon of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and colleagues. That makes the tooth at least 20,000 years older than the oldest of the three previously discovered Denisovan fossils — a finger fragment and two teeth — the scientists report July 7 in Science Advances. All four Denisovan specimens were unearthed in Siberia’s Denisova Cave.

Slon’s group extracted an almost complete set of mitochondrial DNA from the youngster’s tooth. Mitochondrial DNA typically passes from mothers to their children. Investigators also obtained a small amount of nuclear DNA, which is inherited from both parents.

Comparisons of the ancient child’s DNA with that of the three other Denisovans, 10 Neandertals, five ancient humans, five present-day humans, a chimp and a roughly 400,000-year-old member of the Homo genus from Spain (SN Online: 3/14/16) enabled identification and approximate dating of the find. Previous dating of sediment layers in Denisova Cave helped to narrow down the fossil’s estimated age.

Despite Denisovans having inhabited the mountainous region around Denisova Cave for tens of thousands of years, the four fossil individuals attributed to the ancient population display relatively low levels of genetic diversity, the scientists say. Lack of diversity may be due to a small Denisovan population having inhabited one part of Asia for a long time. Or perhaps Denisovans lived elsewhere in Asia and evolved more genetic diversity than observed at the cave. The researchers say only discoveries of Denisovan fossils at additional sites can address that possibility.