How does the Claim of "a Common Ancestor" Benefit Evolution?

Set Up:

In another question, someone who is a Creationist opined,

"A correct understanding of the Bible allows for adaptation of a species within that species.

"Please prove one species has evolved into another.

"Fairy tale says that frog plus kiss from a princess equals prince. Evolution says that frog plus time equals prince. I don't buy it."

To the above, a self-styled expert in Evolution, but who apparently lacks basic logic skills answered:

"I really just wanted to tell you that you need to retake first grade biologist. I just proved everything with these links. Do you even understand evolution? We all had a comm ancestor... monkeys didn't turn into humans... I'm not even gonna explain it."

Apparently, the person thinks that the Creationist doesn't understand that (according to Evolutionist mythology) man didn't come from the ape, but that man and ape both came from some common proto-man/ape. This, he thinks, is beyond the grasp of the Creationist. That (that his claim is un-understandable to someone who can reason and understand the meanings of words) is the ONLY thing the Evolutionist got right. His assumption that man and ape came from a common ancestor in no way refutes Creation, nor does it answer the Creationist's challenge.

The Creationist asked the Evolutionist to "Please prove one species has evolved into another." To this, the Evolutionist answered, "We all had a comm ancestor... monkeys didn't turn into humans... I'm not even gonna explain it." It becomes painfully obvious that he can't explain it to the Creationist because it is nonsense. The challenge was "Please prove one species has evolved into another." In no way is that a claim that man came from the ape, nor does it answer the challenge to assure the Creationist that neither the man came from ape nor the ape came from man, but both came from something else.

The problem is, the Evolutionist still can't seem to prove one species becoming a different one, because now he has one species becoming TWO or MORE species, and yet he still hasn't shown that a species can become ONE other species! Maybe his first grade biology teacher can explain to him the difference between "one" and "many"?

So, here's the challenge:

"Please prove one species has evolved into another."

Show a pig becomning a cow.

Or a frog becoming a prince.

Or a duck becoming an egret.

Evolutionist, CAN YOU SHOW THAT HAS EVER HAPPENED?