Hi Andrew,
So, you are sticking with Robert on this one? Can you not both see how inconsistent your position is? To agree that at this particular moment in time a number of species
do face a threat of extinction, but not to accept that in the long history of life on earth a significant number of other species must actually have succumbed to the threat. You both complain about the lack of a precise definition for "species", but isn't the truth of the matter that you rely heavily on this alleged lack of a definition? It is very convenient for you. Whatever example I may give you of an extinct creature -passenger pigeon, dodo, mammoth, brontosaurus - you will simply say "Ah yes, but enough research would show that it wasn't actually a
species."