 The scratches are thought to be at least 39,000 years old, because they were found below a layer of undisturbed sediment of that age in which hundreds of Neanderthal stone tools were discovered.The attribution of the scratches to Neanderthals is disputed.Matt Pope of University College London cautions that "linking them directly to Neanderthal populations, or proving Neanderthals made them without any contact with modern humans is harder.