Small amounts of Neanderthal DNA discovered in the dust of Spanish and Russian caves could give researchers new insight into how our early ancestors lived.
The 100,000-year-old discoveries were made in three different spots: the Galeria de las Estatuas cave site in Burgos, Spain and the Chagyrskaya and Denisova caves in the Altai Mountain range in Russia.
Traditionally, DNA has been extracted from fossils or bones.
'The dawn of nuclear DNA analysis of sediments massively extends the range of options to tease out the evolutionary history of ancient humans,' said the study's lead author, Max Planck Institute for Evolutionary Anthropology researcher Benjamin Vernot, in a statement.
One of the cave site, Galería de las Estatuas cave site in northern Spain, where researchers were able to extract Neanderthal DNA via cave dust
The Galeria de las Estatuas cave site is located in Burgos, Spain. As far back as the mid 19th century, researchers combed the site for historical finds
The Chagyrskaya cave also provided Neanderthal DNA that let researchers show off the new technology that could be used to open up 'large parts of human history' for more analysis
This shows Chagyrskaya cave in the Altai Mountains in Russia, where researchers also found more Neanderthal DNA via cave dust or sediment
With no fossils or tools used in the study, this allows researchers to open up 'large parts of human history' for genetic analysis that were not available previously.
'We can now study the DNA from many more human populations, and from many more places, than has previously been thought possible,' the study's co-author, Matthias Meyer added.
More than 150 sediment samples were analyzed from the three caves, two of which had previous discoveries where DNA was extracted and analyzed from bones.
That allowed the researchers to compare the new method to get a better idea of what to expect.
They also found there were two 'radiations' or variants of the Neanderthals when they compared the sediment DNA to skeletal DNA.
The older Estatuas population came from one variant, while the younger population was tied to the second form.
It's unclear what caused the variance, but study co-author Juan Luis Arsuaga posited it might be tied to climate change or changes in Neanderthal morphology.
This is a view of of pit 1 at the Galería de las Estatuas, Spain, alongside a stratigraphic column with ages of the soil in thousands of years
The use of the new technology could allow researchers in other parts of the world, notably in China and India, where Neanderthal and, especially Denisovan, remains have been found in abundance.
However, researchers have to be careful with the new method so as not to extract DNA that could be irrelevant, say from a mammal.
'There are lots of places in the human genome that are very similar to a bear's DNA, for example,' Vernot added.
'We wanted to be confident that we weren't accidentally looking at some unknown species of hyena.'
Finding DNA in cave dirt and dust could eventually lead to further study of the Denisovans, as well as other early groups, such as Homo floresiensis, a group that lived in Indonesia more than 50,000 years ago, The Guardian reports.
'The techniques we developed are very new, and we wanted to be able to test them in places where we knew what to expect,' Meyer explained.
A close relative of modern humans, Neanderthals went extinct 40,000 years ago
The Neanderthals were a close human ancestor that mysteriously died out around 40,000 years ago.
The species lived in Africa with early humans for millennia before moving across to Europe around 300,000 years ago.
They were later joined by humans, who entered Eurasia around 48,000 years ago.
The Neanderthals were a cousin species of humans but not a direct ancestor - the two species split from a common ancestor - that perished around 50,000 years ago. Pictured is a Neanderthal museum exhibit
These were the original 'cavemen', historically thought to be dim-witted and brutish compared to modern humans.
In recent years though, and especially over the last decade, it has become increasingly apparent we've been selling Neanderthals short.
A growing body of evidence points to a more sophisticated and multi-talented kind of 'caveman' than anyone thought possible.
It now seems likely that Neanderthals had told, buried their dead, painted and even interbred with humans.
They used body art such as pigments and beads, and they were the very first artists, with Neanderthal cave art (and symbolism) in Spain apparently predating the earliest modern human art by some 20,000 years.
They are thought to have hunted on land and done some fishing. However, they went extinct around 40,000 years ago following the success of Homo sapiens in Europe.