International scientists have uncovered prehistoric human DNA from caves without bones, an advance that could shed new light on human history and evolution.
The study published in the journal Science is based on 85 samples from sediments dating to the Pleistocene, a period that extended from 550,000 years ago until 14,000 year before the modern era.
The samples came from eight caves in Belgium, Croatia, France, Russia and Spain.
These archeological sites are already well known to have been occupied by long-lost cousins of modern humans, Neanderthals and Denisovans, as well as by a variety of animals that are now extinct.
"This work represents an enormous scientific breakthrough," said Antonio Rosas, scientist at Spain's Natural Science Museum in Madrid.
"We can now tell which species of hominid occupied a cave and on which particular stratigraphic level, even when no bone or skeletal remains are present."
To uncover human traces, scientists relied on analyzing fragments of mitochondrial DNA.
"The technique could increase the sample size of the Neanderthal and Denisovan mitochondrial genomes, which until now were limited by the number of preserved remains," explained Spanish National Research Council scientist Carles Lalueza-Fox.
"And it will probably be possible to even recover substantial parts of nuclear genomes."