Neanderthal population number and density were falling long before modern humans made it to Europe
The mitochondrial DNA of six Neanderthals—recently acquired from skeletons found across Spain, Croatia, Germany, and Russia—sheds new light on why the Neanderthals may have died out.
Despite being unrelated, these individuals were remarkably similar at the genetic level—possessing three times less genetic diversity than is found in present-day Europeans.
If widespread, such a loss of genetic diversity would have hit the Neanderthals hard, making it difficult for them to reproduce and leaving them with a weakened ability to fight diseases.
All we know for certain is that by 40,000 years ago the last of the Neanderthals had died out, and another branch of the human family tree was lost.
But before this happened, Neanderthals and modern humans produced hybrid children, who over the course of many generations were absorbed by the newcomers in Europe.
The Neanderthals may be gone but their genes live on in us.