If you think "macroevolution" entails the descendants of dogs one day being something other than dogs, then your notion of "macroevolution" isn't anything to do with evolution at all. They can no more not be dogs, than can any descendants you may have not have you as an ancestor. You would not say "prove to me that 2 = 9, or I will not accept mathematics", would you?
Yes, that's the problem with evolution. Dogs will always have dog descendants. This would mean other species would not be able to form.
They already have! What you you think domesticated dogs, jackals, coyotes, dingoes and wolves are?
They are all dogs
("dogs" are not a single species); but they're not all the same species
, are they? Similarly, cougars, panthers, jaguars, lions, tigers, ocelots, lynxes, leopards, cheetahs, snow leopards, wildcats, sand cats and "domesticated" cats are all cats
- but they are clearly not one species
"All descendants of dogs are dogs" and "all descendants of cats are cats" is precisely what we would expect of evolution
, by the definition of what "dogs" and "cats" are. By the same token, "all descendants of mammals are mammals" and "all descendants of marsupials are marsupials" are also
That is not a problem for evolution: it is, in fact, precisely what we would expect if it were true
: one can never escape one's ancestry.
However, that does not
mean that population groups cannot bifurcate into distinct population groups that become reproductively isolated and develop along different lines, even with radically different appearances and ecological niches.
It's not a problem for evolution, but a problem with your own understanding. I suspect that here you're stuck on a definition of "species" you have in your head that isn't the same as the biological one. You also appear to think that "dogs will always be dogs" and "dogs can speciate" are mutually exclusive propositions when they are not. Perhaps that's a good place to start?
This doesn't explain how dogs, cats, and flies individually formed.
As it happens, we can
tell from genetics, anatomy and the fossil record somewhat of the lineage of both dogs and cats. But that's a separate question - let's not get ahead of ourselves... do you understand why "all descendants of dogs are dogs" is precisely what is expected if evolution is true, and therefore, not
a "problem" for it?