[VadeRetro]

I acknowledged the cross fertilization of donkeys and horses BUT a mule cannot procreate so is NOT a viable life form on it's own.

Exactly my point. They have speciated. Those populations can never re-merge to a single species. They can only drift further apart.

By comparison, a variety can disappear by re-melding into its parent stock (presumably after some barrier disappears and contact is reestablished). I saw a report once that the Baltimore oriole, a variety of eastern oriole and not a baseball team, was disappearing in this way but have no idea if it's still happening.

[Texasforever]

Those populations can never re-merge to a single species

Then how can a trans-muted species EVER come into being? If cross fertilization does not produce a fertile offspring to propagate itself then where is mechanism for continued evolution?