The mouth of Baishiya Karst Cave nestles near the base of a towering crag at the edge of the Tibetan Plateau. Strands of colorful prayer flags crisscross the pale face of the hollow, a holy location where Tibetans have long retreated to pray and heal from sickness. Within the cave’s cool confines in 1980, a local monk happened on something unexpected: a jaw with two huge teeth that, while human, was definitely not like that of humans today.

A study published today in Nature reveals just how much this ancient jaw has to say. A detailed analysis of its physical features as well as proteins extracted from the fossil suggest that the mandible, dated to 160,000 years ago, comes from