One mistake evolution advocates make.

[Brian37]

No matter how simple it is made, the mind of the denier is even more simlpe.

True, but for those who are interested in it and accept it, when they turn and repeat it themselves the accuracy helps. 

I like the way Dawkins describes DNA in that it is not like mixing paint, but more like shuffling a deck of cards.

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Common ancester is a recognized term in biology.  For example LUCA - Last Universal Common Ancester - is the term for the hypothetical ancesteral organism on the line of descent to us that is evolutionarily closest but still equidistant from all current lineages of life on earth.

Yes as in species. But not as in a specific individual single pair of that species. There is no way to single out an individual pair in that context, just the genes that are labeled as a specific species. It is better to call that species our common ancestors not a single pair. Even today, parents can have brothers and sisters on top of multiple offspring whom go on to have their own brothers and sisters. So it is not good to say "common ancestor" otherwise why call our primate ancestors our "cousins"? 

And again, It is accepted in science to say "common ancestor", that part is true. But just like the word "law" laypeople, especially fundies confuse that with a "lawgiver" and it does not mean the same thing. 

Like I said, there was no first pair of DNA, there were first conditions that lead to countless strands of DNA. Just like there is no "first couple" hurricanes, but a season as to which multiple hurricanes happen, even at the same time in different parts of the world because of conditions. It is possible to have more than one hurricane in the Atlantic at the same time.