Agreed, but then they never become anything but dogs do they - just different infraspecific taxa within the canine species. Your point being to falsify evolution even more? And btw, it didn't start with one canine infraspecific taxa, but at he minimum of two.
The point being no matter how far you go back you are presented with the same problem - that infraspecific taxa would not become anything else until it mates with another infraspecific taxa in the species.
ALL dogs are the same species - just different infraspecific taxa in that species. Whether human intervention or geological changes forcing them together, the most they can become is infraspecific taxa - if you stop ignoring your own science that is.
https://en.wikipedia.org/wiki/Species
"Presence of specific locally adapted traits may further subdivide species into "infraspecific taxa" such as subspecies (and in botany other taxa are used, such as varieties, subvarieties, and formae)."
You will NEVER get another species - only other infraspecific taxa within the species..... Unless of course they incorrectly classify things and ignore their own scientific definitions, which of course they do daily.