Aside from this, they’ve also determined the time of Neanderthals’ disappearance. They surmise this species might have survived but in dwindling populations before their extinction. Researchers believe the extinction of Neanderthals didn’t occur rapidly.
Despite this, there’s no evidence showing that Neanderthals and early humans lived closely together.

For the past six years, researchers built mathematical models that combine new radiocarbon dates with archeological stratigraphic evidence.

They’ve discovered the groups interacted with each other for a significant period of time which gave them ample time for interbreeding.

Thomas Higham from Oxford University obtained new data from 200 bone, charcoal and shell samples from 40 European archeological sites.

Higham explained that other recent studies on Neandarthal and modern human genetic make-up suggest that there was an interbreeding outside of Africa.

The study also showed that 1.5 percent to 2.1 percent of the DNA of modern humans originated from Neanderthals, he said.

There seems to have been a more complex picture characterized by a biological and cultural mosaic that lasted thousands of years.
Higham explained that previous radiocardbon dates have often underestimated the age of samples from sites associated with Neanderthals because organic matter on the sites was contaminated by modern particles.

To get the results, researchers used ultrafiltration methods that purified extracted collagen from the bone and avoided risk of modern contamination.