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ALMOST a decade ago, researchers sequenced DNA from an ancient bone fragment to reveal that it belonged to a woman from an entirely new group of humans. After years of waiting, we are now getting our first glimpse of the only confirmed home of the Denisovans.

Named after the Denisova cave in Siberia, where the ancient bone was found, these humans lived in Stone Age Eurasia alongside our species and the Neanderthals. Although we have discovered more about these people since the bone was discovered (see 鈥�Who lived in a cave like this?鈥�), we have heard very little about Denisova cave.

That has now changed after an international team of researchers published two papers that make it clear the cave is every bit as extraordinary as its ancient occupants. Not only do the papers give us a better understanding of who lived there and when, they reveal some of the objects those residents made. 鈥淪ome of the material is beautiful,鈥� says Thomas Higham at the University of Oxford. 鈥淲e think it may be the earliest of its kind in Eurasia.鈥�

鈥淪ome of the material is beautiful. We think it may be the earliest of its kind in Eurasia鈥�

Denisova cave lies in the Altai mountains of southern Siberia, a few hundred kilometres from the Russian border with Kazakhstan, Mongolia and China. Higham says the place is 鈥渁lmost magical鈥�, with its Alpine-like scenery, wild horses and soaring eagles. 鈥淚t鈥檚 rather like Switzerland, but without as many people,鈥� he says.

The cave has become a major draw for archaeologists. Michael Petraglia at the Max Planck Institute for the Science of Human History, Germany, visited last year. 鈥淚t was a great experience,鈥� he says. 鈥淲hen we were in the cave, it was cold inside, and the excavators told us the sediments are sometimes frozen. This helps to ensure that the DNA gets preserved.鈥�

Lying at the heart of a large river valley, the cave was also attractive to Stone Age humans. The new research concludes that Denisovans and Neanderthals both lived there at various points over the past 300,000 years (Nature, ). Our species, Homo sapiens, probably occupied the cave within the past 50,000 years.

Russian archaeologists have been working there for about 40 years, and continue to lead the investigations. Over the years, they have excavated several metres of sand and dirt from two of the cave鈥檚 three chambers 鈥� the main and east chambers 鈥� and they have just started excavating the third, the south chamber.

In the process, they have discovered thousands of artefacts, says Richard Roberts at the University of Wollongong, Australia, although most of the information regarding these is recorded in Russian language publications.

Roberts first got involved in investigations at the site in 2011, after the Denisovans鈥� discovery. He says it is often extremely difficult to work out the age of dirt layers in caves. 鈥淵ou don鈥檛 have nice and simple layers one after the next after the next, with nothing happening afterwards. Things happen in caves.鈥�

Most obviously, animals including hyenas moved into the cave whenever it was abandoned by humans. In the process of digging their dens, the hyenas mixed up some of the dirt layers in a few sections of the main and east chambers. Complicating things further, there are some significant time gaps in the sequence. For instance, using an optical dating method that establishes the age of sandy deposits from when they were last exposed to sunlight, the researchers found that a 60,000 to 70,000-year-old layer lies directly beneath a layer that is no more than 44,000 years old.

鈥淎rchaeologists think the bone artefacts recovered were crafted by the Denisovans themselves鈥�

That is particularly unfortunate because some of the most noteworthy finds from the cave 鈥� those known as the Initial Upper Palaeolithic artefacts 鈥� come from layers of dirt that lie very close to this time gap, making it difficult to be sure how old they are.

These include a bracelet of polished green rock discovered early in the 2000s. The only way to work out its age would be to use optical dating on sand grains immediately around it. But such grains weren鈥檛 gathered when the bracelet was found so we may never know when it was made.

Fortunately, sand grains are now routinely collected alongside all Initial Upper Palaeolithic finds. Last year, for instance, a bit of what has been described as an ivory tiara was dug up. 鈥淲e were there when they found the tiara,鈥� says Roberts. 鈥淪o we collected sediment samples from the vicinity for dating. We鈥檙e just waiting for the authorities to export them from Russia to Australia.鈥�

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The archaeologists have also unearthed Initial Upper Palaeolithic rings, beads and bone sewing needles. A few bone pendants have now been carbon-dated, with the oldest being about 45,000 years old (Nature, ). It is these artefacts that Higham thinks may be the oldest of their kind in Eurasia.

But which human inhabitants of the cave made them? 鈥淲e think that the Initial Upper Palaeolithic bone [artefacts] recovered from Denisova cave were produced by the Denisovans,鈥� says Michael Shunkov at the Siberian branch of the Russian Academy of Sciences, who now leads the investigations.

It is certainly possible, says Roberts. Neanderthals would have been long gone from the cave by this time, but the youngest of the Denisovan bone fragments found there appear to be just 50,000 to 55,000 years old. 鈥淭he Denisovans did persist at the cave until quite recently 鈥� certainly recently enough that they could have made some of those Initial Upper Palaeolithic artefacts,鈥� he says.

If so, the finds give us a first glimpse of how the Denisovans lived and behaved. Take the curious rows of dots carved into some of the needles. 鈥淚t鈥檚 terribly difficult to work out what they mean, but they could be marks of ownership or just purely decorative,鈥� says Higham.

Of course, it is possible that the artefacts were made by H. sapiens instead. But in that case, the finds are significant for another reason, says Higham. We know that some of the artefacts are about 45,000 years old and that similar finds are unknown in Europe until about 43,000 years ago. So H. sapiens may have pushed as far east as the cave before heading west to Europe, says Higham.

The best way to establish the probable identity of the craftspeople at the cave is to find fragments of bone or human genetic material in the layers that hold the Initial Upper Palaeolithic artefacts. But the chances of discovering those in just the right layers is relatively low: even after decades of investigation, researchers have identified only about a dozen bone fragments in the whole cave, including three described for the first time in the new papers.

Instead, the team is pinning its hopes on new techniques that extract human DNA from samples of dirt even if no fragments of bone are present.

There is also the tantalising possibility that the team will find more spectacular rings, bracelets and pendants 鈥� and be able to pin down the identity of the humans who made them 鈥� as the excavations continue. 鈥淪outh chamber has hardly been touched at all,鈥� says Roberts. 鈥淚t鈥檚 still filled with sediment. It might hold some great stuff. This really is the site that keeps on giving.鈥�