There’s a long-running controversy among scientists about whether or not early humans interbred with Neanderthals,and if they didn’t, why not? Now DNA has answered the first question by revealing that modern humans show evidence of Cro-Magnon ancestry, but there’s no evidence we had Neanderthal ancestors.
Neanderthals and our early human ancestors were distinct species, although they lived during the same period, often side by side. If they didn’t interbreed, what stopped them? It could have been that they were too distinctly separate to produce offspring, although this is doubtful.