I think, Dr. Teixera simply misspoke. Neanderthals have never been considered a distinct species from humans, nor should they, because humans and Neanderthals

I think, Dr. Teixera simply misspoke. Neanderthals have never been considered a distinct species from humans, nor should they, because humans and Neanderthals probably had fertile offspring. The moment you talk about extinct species, the terminology falls apart. At some point (about 6.5Ma ago), the ancestors of humans and chimpanzees were one species. Humans and chimps are clearly distinct species. With extant difficult cases (ring species), you take the transitive closure; do that for all extinct species, and there are no species anymore. So what can you do? Apply an arbitrary cutoff and argue endlessly whether Neanderthals were a subspecies of humans but homo erectus wasn't? Or just give up, use the terms species, subspecies, clade and population interchangeably. Population genetics apparently decided to give up and picked "population" as a neutral term.