Early modern humans and Neanderthals probably did not interbreed, according to evidence collected by Italian scientists.
Neanderthal man: Interbreeding debate continues
Researchers have long considered Neanderthals and the humans that lived in Europe 30,000 years ago as distinct species, even though they lived side by side.
However, there is controversy over theories that Neanderthals made a contribution to the gene pool of people living today.
This has been fuelled by a skeleton uncovered in Portugal that appears to show both Neanderthal and human features.
The latest research, from the University of Ferrara in Italy, compared genetic material from Neanderthals, Cro-Magnon humans and 21st-Century Europeans.
The DNA from the Neanderthals and Cro-Magnons was taken from their bones.
The genetic material was extracted from cell structures called mitochondria rather than the nucleus.
The scientists found that while, unsurprisingly, modern humans show clear genetic signs of their Cro-Magnon ancestry, no such link between Neanderthal DNA and modern European DNA could be established.
The results, they say, indicate that Neanderthals made little or no contribution to the genes of modern humans.
Out of Africa
The mitochondrial DNA of the two ancient species was very different, claims the study.
"This discontinuity is difficult to reconcile with the hypothesis that both Neanderthals and early anatomically modern humans contributed to the current European gene pool."
The finding are said to support the theory that the "anatomically modern human" arose in Africa some 150,000 years ago and then dispersed across the globe, displacing the Neanderthals on the way.
It is a blow to the so-called multi-regional theory, in which some interbreeding between Neanderthal and early humans is said to have taken place.
The latest study is reported in the journal Proceedings of the National Academy of Sciences (PNAS).