The elusive Denisovans, extinct cousins of modern humans, have only left a few hints of their existence in the world.
Their DNA persists in some modern human populations such as Indigenous Australians, and a handful of fossils have been uncovered at a few sites across Asia.
Now, a new trove of fossils and tools has been found in a cave in south-western China.
The cave, which has since been severely damaged by quarrying activity, yielded seven remains identified as Denisovan, alongside thousands of other bone fragments and tools.
The discovery is described in two papers published in the journal Nature.
Bo Li, an archaeologist at the University of Wollongong and co-author on one of the papers, said the objects surrounding the Denisovans could allow us to learn more about them.
"The fossils are directly associated with stone tools, bone tools, animal remains and environmental evidence, allowing us to study Denisovan biology, technology, diet and adaptation together," Professor Li said.
Fossils excavated before cave collapse
Denisovans, which are a close relative of modern Homo sapiens, were first identified from DNA analysis of a single finger bone unearthed in Denisova Cave in Siberia in 2008.
Since then, a handful of bones and teeth attributed to the mysterious human have been found on the Tibetan Plateau in China, Laos and Taiwan and a skull in north-east China.
The new batch of fossils was unearthed from Bianfu Cave, in the Chinese province of Yunnan, in 2019.
"Getting an idea that [Denisovans] were not just isolated hominins living up in Siberia … is very exciting," Mike Morley, an archaeologist at Flinders University not involved with the latest discovery, said.
The cave had to be urgently excavated because nearby engineering work was causing the mountain it was in to collapse.
The researchers extracted some 60,000 bone fragments and thousands of stone artefacts before the entrance was destroyed and the site rendered inaccessible.
The researchers identified a protein signature belonging to Denisovans in seven of the excavated bone fragments: an arm bone, two skull shards and four teeth.
Dating of sediment layers indicated the fossils were between 134,000 and 167,000 years old, while the cave appeared to have been used from 190,000 until 70,000 years ago.
Piecing together evidence of Denisovan life
Professor Morley said objects found around the fossils could tell us about the Denisovans' lifestyles.
"This is something we've never had a good idea on," he said.
Previous Denisovan sites have also been used by Homo sapiens and other early humans, like Neanderthals, making it hard to tell what the Denisovans themselves left behind.
Pollen and animal traces around the site suggest the Denisovans lived in a forested area dominated by conifers.
"The Denisovans at Bianfu Cave lived in a relatively predictable forest or forest-steppe environment and focused on locally available animal resources," Professor Li said.
Bones found in the cave carry marks and scratches that imply the Denisovans hunted animals like deer and water buffalo.
"[This] indicates the animals were brought to the cave or processed there for meat, marrow and grease," Professor Li said.
The researchers also found stone and bone tools similar to those used by Neanderthals.
Professor Li said it was unlikely Denisovans from other areas would have followed identical lifestyles.
"The Bianfu Cave provides an important example, but we need more evidence from the other sites to test if this applies to all Denisovans," he said.
The Denisovans' huge range from Siberia through to Tibet and South-East Asia suggest they could adapt well to new environments.
Professor Morley said it was a "pity" the cave was now inaccessible, but recent interest in Denisovans would drive more discoveries.
"I don't think it will take too long before we have another site, probably more than one site, where we start getting Denisovan stuff," he said.
