I often see Neanderthals referred to as Homo sapiens neanderthalensis, so it's not quite as clear cut that they're a separate species. And indeed, by the defini

I often see Neanderthals referred to as Homo sapiens neanderthalensis, so it's not quite as clear cut that they're a separate species. And indeed, by the definition of "a population that can interbreed and produce viable offspring", if many of us have Neanderthal genes then we would be the same species.