The first Denisovan forearm bone came out of a 22-sample shortlist

Six to 16 endogenous proteins were identified from each of the five specimens, covering 1,972 to 4,076 amino acid residues.

All five samples carried the Denisovan-specific variant COL1A2 R996K, indicating their Denisovan identity.

None of the five specimens had protein variants specific to H. sapiens or Neanderthals.

The area around Bianfu Cave has been heavily quarried, destroying much of the cave including the entrance; in 2019 local workers spotted animal fossils and alerted authorities, leading Hao Li and colleagues to conduct a rescue excavation that summer.

The newly discovered radius has a large head, where it connects to the humerus at the elbow, more similar to Neanderthals than to modern humans, but its overall shape is more similar to modern-human radii.

The team dug three trenches to a depth of 6.6 metres, revealing 18 layers of sediment, of which 10 contained artefacts made by hominins; one layer yielded four intact hominin teeth.

Study co-author Qiaomei Fu, director of the Ancient DNA Laboratory at the IVPP, Chinese Academy of Sciences, told Live Science by email that the human-like radius shape "likely provided functional advantages for lightweight, precise manipulation".

The excavation unearthed over 64,000 fragments of bone.

Five human fossils dating to between 134,000 and 167,000 years ago confirmed that the people who used the cave were Denisovans; paleoproteomic analysis confirmed five hominin remains as Denisovans.

ZooMS analysis confirmed that two parietal bone fragments (BFD767 and BFD769) and one proximal radial fragment (BFD771) came from hominins.

BFD767 and BFD771 came from Layer 7, dated to approximately 148,000-134,000 years ago; BFD769 came from the older Layer 9, dated to approximately 167,000-150,000 years ago.

The team also analysed two hominin teeth from Layer 7: a lower fourth premolar (YHB3518) and a lower second molar (YHB3075).

Abundant amelogenin Y isoform peptides in the enamel of the two teeth indicate both teeth belonged to male individuals.

The team tried to extract DNA from the three bones without success; Fu says the region's warm climate and the age of the fossils were unsuitable for DNA preservation.

Two studies on Bianfu Cave were published on Wednesday, Sept. 9, in the journal Nature.

The proteomic study was conducted by a research team led by Professor Fu Qiaomei of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, with multiple collaborating institutions.

The hominin fossils are dated to about 167,000-134,000 years ago, whereas the cultural sequence at the cave spans about 190,000 to 70,000 years ago.

The Nature paper describes the Bianfu record as one of the longest cultural records most parsimoniously attributed to Denisovans, identified through enamel-dentine junction morphology and palaeoproteomic analyses.

The excavators found 1,366 stone artefacts, including 135 flakes and the cores they came from plus simple tools such as scrapers and choppers, relatively simple compared with those made by Neanderthals elsewhere in Eurasia at the same time.

The team found 1,654 identifiable animal bones, including large numbers of deer and bovids plus rhinoceroses, hyenas and bamboo rats; many bones had marks suggesting butchery by hominins and few showed gnawing by non-human animals.

Faunal and pollen records indicate a conifer-dominated forest or forest-steppe environment across Marine Isotope Stages 6 to 4, and the inhabitants practised specialized hunting of medium- to large-bodied prey with expedient core reduction alongside pervasive use of unmodified bones.

Bence Viola of the University of Toronto, who was not involved in the study, says the new site is only the third Denisovan locale "where we have everything" - human remains, lithics, fauna and environmental context - the other two being Denisova Cave in Siberia and Baishiya Karst Cave on the Tibetan plateau.

The recovery rate of hominin fossils from ZooMS screening has been extremely low, only 0.1% at sites such as Denisova Cave and Baishiya Karst Cave.

Denisovans are known from only a handful of fragmentary fossils scattered from Siberia to Laos, and no complete Denisovan skeleton has ever been found.

The dated hominin fossils cover about 33,000 years, roughly 28 percent of the cave's approximately 120,000-year cultural sequence.

Adding Bianfu Cave takes the number of Denisovan sites with remains, stone tools, fauna and environmental context together from two to three.

Researchers first went through the bone fragments by hand and identified 22 potential hominin remains, which they then subjected to molecular analysis.

The researchers developed a "morphological pre-screening + ZooMS identification" strategy because running ZooMS on all of Bianfu Cave's fragments would be costly and inefficient, and they present it as a replicable framework for similar Paleolithic sites with abundant bone fragments.

Because the bones and teeth appear to be different ages, Hao Li's team concluded that they come from at least four individuals.

Three hominin identifications from 22 fragments submitted to ZooMS is a hit rate of about 13.6 percent.

A 13.6 percent hit rate within the pre-screened subset is roughly 136 times the 0.1 percent hominin recovery rate reported for blind ZooMS screening at Denisova Cave and Baishiya Karst Cave.

Testing 22 fragments instead of more than 64,000 is about 2,900 times fewer mass-spectrometry runs.