[BetaDeltaAlpha]

> You can make the exact same argument about “species”

There's a clear line in this case: A species is a group of any living beings that can produce fertile offspring.

Donkeys and Horses are separate species because they breed and produce Mules which cannot reproduce.

[Amezarak]

Nope, not only is that not the definition of species, it’s not even true in the case you mention - mules are sometimes fertile.