Your objection is a moving target.
First, you said that no mutation has ever improved a species. I showed that, in fact, they have.
Next, you then asked if mutations have improved
complex species. I showed that, indeed, they have.
Now you're saying that microevolution (the thing you rejected in your previous two statements, and microevolution is the direct result of mutation and natural selection) is true, and it's
macroevolution that's false. I wonder what'll happen when I show that it is, in fact, true?
Speciation is an example of macroevolution, and this is readily demonstrable in the lab, as well as in nature. TalkOrigins has
a convenient list, but the examples are endless. The Hawthorn fly, for instance, has speciated due to the introduction of new fruits (
source). The cichlid fish has speciated by water clarity (
source). Palm trees on the same island have speciated based on soil preference (
source). All are instances of speciation, and of macroevolution. It's not some hypothetical, long-term consequence of the theory, it's an observable phenomenon.
Can you prove this?
Let's say it's true, just for kicks. Would that affect the veracity of the theory?
Yes, they do. 'Race', in Darwin's era, referred to varieties within a species, not just human races as the term is used today. For example, on page X, this is how Darwin used the word:
"
Nevertheless, as our varieties certainly do occasionally revert in some of their characters to ancestral forms, it seems to me not improbable, that if we could succeed in naturalising, or were to cultivate, during many generations, the several races, for instance, of the cabbage, in very poor soil (in which case, however, some effect would have to be attributed to the direct action of the poor soil), that they would to a large extent, or even wholly, revert to the wild aboriginal stock." -
On the Origin of Species, p15.
Clearly, Darwin was advocating a racial purge of the cabbages.