A 160,000-year-old Denisovian jawbone discovered in a cave on the Tibetan plateau provides evidence of the presence of this ancient human group far from the Denisova cave in Siberia. A jawbone, described in this week's issue of Nature, represents the oldest known hominid fossil on the Tibetan plateau. This discovery indicates that Denisovans adapted to high-altitude, oxygen-poor environments long before the arrival ofHomo sapiens.
The Denisovans are an extinct brother-group of the Neanderthals, known only from fossil fragments discovered in the Denisova cave in southern Siberia. Traces of their genomes can also be found in some of today's Asian populations. In particular, Sherpas, Tibetans and neighboring populations display a genetic characteristic derived from Denisovans, and essential for prolonged life in high-altitude conditions. However, the reason why Denisovans developed this adaptation was not understood until now, as fossil evidence of their existence remained confined to the Denisova cave, located at an altitude of just 700 meters.
Jean-Jacques Hublin and his colleagues describe a hominin mandible discovered in the Baishiya cave on the Tibetan plateau at an altitude of 3,280 meters. Analysis of the proteins contained in this bone has identified it as belonging to the Denisovans. Radioisotope dating indicates that it is at least 160,000 years old. This age predates the earliest evidence of human presence at such an altitude on the Tibetan plateau (around 30,000 to 40,000 years). The altitude at which this fossil was found could explain why Denisovans possessed genetic characteristics that enabled them to adapt to low-oxygen environments. The age of the jaw is compatible with the oldest Denisovian fossil currently known from Denisova Cave, and shares certain characteristics with previously described Denisovian fossils, such as the large size of the teeth. The discovery also links other Chinese fossils to this group. Taken together, these results provide a better understanding of the evolutionary history of hominins in East Asia.
