Some of the bones contained Neanderthal DNA, it turned out. But in 2010, Max Planck researchers discovered that one finger bone held different genes from an unknown human lineage.

Over the past decade, scientists have discovered more Denisovan teeth and bone fragments, including a chunk of a skull. Denisovans appeared to have lived in the cave, off and on, from 287,000 years ago to about 50,000 years ago.

Judging from their DNA, Denisovans shared a common ancestor with Neanderthals about 400,000 years ago. They interbred with Neanderthals and with our own species. Today, people in East Asia, Australia, the Pacific islands and the Americas all carry some Denisovan DNA.

The spread of Denisovan DNA in living humans strongly suggested that they may have lived throughout East and Southeast Asia. And maybe not just there: Earlier this month, a team of researchers argued that a population of Denisovans reached New Guinea and interbred further with modern humans.

But year after year, no one could find a Denisovan fossil outside the Siberian cave.

In 2010, Dongju Zhang , an archaeologist at Lanzhou University in China, began studying the Tibetan jaw, which had been languishing in storage at her institution.

Right away, she could tell it was humanlike — but not human. “We all have chins, but this doesn’t have one,” Dr. Zhang said in an interview.

Eventually, she located the cave in Tibet where the jaw had been discovered. Monks at a nearby temple told her they regularly found human remains on their visits.