I love you all, but to get back to the original question, please look up the definition of "species" before sharing.
There is only one human species. By definition, that's all there can be. Our nearest past and present relatives, Neanderthal and chimps, are not members of our species, despite the fact that chimps share 99 percent of our DNA. I doubt that genetic drift over even two millenia would make Romulans a species distinct from Vulancanoids (although their buggy TNG foreheads definitely need explanation.)