Ancient human DNA found in 20,000-year-old bone jewellery

The owner of a deer tooth pendant has been identified over 20,000 years after their death.

A group of researchers managed to extract the ancient DNA (aDNA) of a woman from the piece of jewellery, which had been found in Denisova Cave, Siberia. This site is renowned for the extraordinary preservation of prehistoric remains, including those of our non-human relatives.

The team hope that their newly developed technique will allow researchers to discover more about the users and makers of ancient artefacts, revealing more about the culture of our ancestors.

Professor Ian Barnes, an expert on aDNA at the Museum who co-authored the paper, says, 'Bespoke DNA extraction techniques such as this are absolutely critical for studying periods of deep time where there is very limited material to work with.'

'Previous work has recovered aDNA from sources beyond bones, such as soils and sediments, but this new method expands the study of aDNA even more widely. It's fascinating to see how the need for new sources of information drives scientific creativity.'

Dr Matthias Meyer, the paper's senior author, adds, 'While forensic scientists will not be surprised that human DNA can be isolated from an object that has been handled a lot, it is amazing that this is still possible after 20,000 years.'

The findings of the study, led by researchers from the Max Planck Institute for Evolutionary Anthropology, were published in the journal Nature.

The oldest jewellery ever found

Both ancient and modern humans have been making objects for millions of years. The oldest known tools are more than three million years old, and have been linked to species such as Paranthropus and Homo habilis.

Ancient hominins, however, only turned to making other items much more recently, with the earliest jewellery currently dated at around 142,000 years old.

It is thought to have been made by early Homo sapiens living in Morocco, who made holes in sea snail shells to use them as beads. The shells also have traces of red dye on them, suggesting they might have been painted.

It's not just our ancestors who made jewellery, however. Eagle claws found among Neanderthal remains in Croatia appear to have been smoothed down and had notches made in them.

The researchers believe the Neanderthals may have made these modifications so the claws could have been mounted in a necklace or bracelet 130,000 years ago. This is before Homo sapiens is thought to have arrived in Europe, showing that it wasn't only our species who appreciated jewellery.

Because bone is porous, fragments of DNA in the sweat, blood or saliva of ancient hominins could have entered these artefacts as they were worn or made. This makes bone jewellery a potentially rich resource for scientists to study.

However, getting to this DNA is difficult and normally means cutting into the bone. This would mean damaging these rare artefacts, and destroying irreplaceable evidence about how they were made.

Professor Marie Soressi, another co-author on the paper, explains, 'The surface structure of Paleolithic bone and tooth artefacts provides important information about their production and use. Therefore, preserving the integrity of the artefacts, including microstructures on their surface, is a top priority.'

'Attempts to extract DNA from artefacts like these have been used in the past, but they weren't often very effective,' Ian adds. 'They are either not very good at getting DNA from the sample, or produce extracts which contain a lot of contamination from other sources.'

Undeterred by the challenges, the team set out to develop new ways of extracting aDNA from bone without resorting to destructive methods or chemicals.

How can ancient DNA be extracted from bone artefacts?

To develop their new technique, the researchers took detailed images of the surface of 10 bone fragments uncovered during excavations of Palaeolithic sites in France. These were then submerged in four different chemicals which are already used for DNA extraction.

After retrieving the fragments, more images of their surface were taken by the scientists to see if the chemicals caused any damage. Two chemicals had significantly altered the bone, and so were ruled out for future tests.

More bone fragments, which had been tentatively identified as tools, were then put into solutions of sodium phosphate buffer at progressively hotter temperatures. The aDNA released from the artefacts was then sequenced to identify where it came from.

While the researchers managed to extract DNA from the deer bone and ivory artefacts, as much as 98% of the human DNA they found showed no signs of age-related damage. This means it was probably the DNA of the archaeologists who dug up and handled the fragments in the 1970s, rather than from ancient humans.

Despite the initial setbacks, the researchers had proven that their new technique could work. But they needed bone objects uncovered during modern excavations, where the archaeologists had worn masks and gloves to prevent contamination.

The team finally found the opportunity they were looking for when they tested an elk tooth pendant from Denisova cave. Their technique revealed the presence of an 'extraordinary' amount of human aDNA, mostly from one female individual who lived between 19,000 and 25,000 years ago.

Her DNA would have been worked its way inside the bone through extensive handling, either while she made the pendant or wore it. This makes it currently impossible for researchers to tell whether she was the jewellery's maker, wearer, or both.

If more bone artefacts are analysed in a similar way, it might allow researchers to detect cultural patterns. For instance, certain artefacts may have been worn exclusively by one sex, or may only have been made by specific groups of ancient hominins.

The team have called on archaeologists to take steps to prevent these artefacts from being contaminated so that these insights into our ancestors aren't lost forever.