But for a bigger picture question, are all of those others able to interbreed with each other, as well? If yes, they are basically like different races of human or breed of domestic animal. If not, it gets much more interesting in terms of classification.
Does this mean humans are the same species as vulcans, klingons, romulans, betazoids, trill, ocampa, and ktarians?
Presumably yes.
But for a bigger picture question, are all of those others able to interbreed with each other, as well? If yes, they are basically like different races of human or breed of domestic animal. If not, it gets much more interesting in terms of classification.