Mutations disprove the theory of upward evolution

[Esquilax]

a mainstream source "says".
Are you saying actual observation or is it just a conclusion based on assumptions?

Also the definition of species is important.

It's really simple: find me a textbook, or a paper, or a scientist, accepted by the mainstream scientific community, who defines evolution as a process by which we would expect an animal to give birth to something that isn't the same species as it.

Like you said, dogs breed dogs. Since you've claimed evolution says this, find me a single mainstream source that claims that, because evolution is true, we should see dogs breeding something that is not a dog. You go ahead and find that, and I will convert to christianity right here, because that, good sir, would be a miracle.

PS: You know what else is important? The definition of a kind.