Scientists have discovered the first-ever fossil of a Denisovan forearm bone in southwest China's Yunnan Province. This discovery provides new insights into how these mysterious ancient human relatives lived and adapted to their environments.

The new study, led by researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences, in collaboration with multiple institutions, was published in the journal Nature.

The bone, a radius from the lower arm, was found alongside other Denisovan remains at a Paleolithic site called Bianfu Cave in Yunnan. These fossils date back to a period between 134,000 and 167,000 years ago.

Denisovans are an extinct group of early humans who were first identified through DNA extracted from a tiny finger bone found in a Siberian cave in 2010. Since then, scientists have realized that Denisovans were once widespread across Asia, but physical remains have been extremely rare. Most discoveries have been limited to teeth and a few skull fragments.

The research team used a two-step method to find the rare fossils among more than 60,000 bone fragments collected from the cave. Instead of testing every piece, which would have been too costly and time-consuming, they first sorted the fragments by shape and then used a protein-analysis technique to confirm which ones came from ancient humans.

This approach proved highly effective. The researchers identified three Denisovan specimens from two different layers, extending human fossils beyond a single younger layer and including two skull fragments and a forearm bone.

The forearm bone is the most exciting element of the discovery. While it shares some features with arm bones from Neanderthals -- close relatives of modern humans, such as a large upper joint, its overall shape and the geometry of its neck region are more similar to those of modern humans.

"This combination of traits suggests that Denisovans probably had unique movement patterns and behaviors that set them apart from both Neanderthals and our own species," said Fu Qiaomei, a professor from the IVPP.

The discovery also confirms that Bianfu Cave was home to a thriving Denisovan population during a particularly cold period in Earth's history. The relatively warm climate of the Yunnan-Guizhou Plateau at that time, along with plentiful food, likely made the area a safe haven where these ancient people could survive for thousands of years, Fu said.

Before this study, the only rich source of Denisovan fossils with clear stratigraphic context and stone tools recovered outside Siberia was a cave on the Qinghai-Xizang Plateau. The finds at Bianfu Cave now fill a major geographical gap. The researchers believe that the region may have been a long-term habitat for these ancient human groups, helping them endure harsh climatic changes.

The discovery of the forearm bone is especially exciting because it gives scientists a rare glimpse into the physical traits that allowed Denisovans to thrive in diverse environments across Asia. Each new fossil adds a new piece to the puzzle of human evolution, said the study.