Re: Get with the program! @Kiwi
For sexually reproducing organisms I was always taught that they are the same species if they have the same number of chromosomes AND can produce non-sterile offspring. Breed donkey and horse and get a mule or hinny, both of which are (nearly always) sterile, as horses and donkeys have different chromosome counts and are certainly different species.
Different sub-species should always produce non-sterile offspring.
Interestingly did recently read that the modern man/Neanderthal cross-breeding produced reproductively capable females but sterile males; hence no Neanderthal X chromosomes in the current human genome (no matter what the feminists say to the contrary).