Right now, I am completely unsure of the theory of evolution. I haven't studied it much, and from what I have studied, it was from a Christian viewpoint, so my understanding of evolution might be slanted for you more traditional atheists. Personally, I don't think our origin is as an important question to answer as some would lead us to believe.
Obviously since I don't believe in God, I don't believe we were created. But evolution is seriously lacking in proof saying, "Here is where life comes from." It might be able to answer how humans came to be, and maybe their ancestors (assuming they had any), but you can only go so far back, and then what? Granted, just because we don't have the answer doesn't mean an answer doesn't exist. But for me, it is as trivial as they come, and should only be important to those who care about it.
Also, and this refers back to my statement about atheism having poor arguments for the non-existence of God, evolution doesn't necessarily mean God doesn't exist. Atheists, I know, will try to say it does, but as I attempted to explain, evolution doesn't explain how life came to be, it just shows how life progresses (again, assuming it is true).
From my understanding of this topic, earth is estimated to have existed 4 billion years ago, or whatever the new number is, and at its conception earth was uninhabitable to any form of life. Correct me if I'm wrong. If this is true, then we need to seriously question how life came to be on earth, for those interested. You could try to prove spontaneous life, but that has been debunked with the famous maggot experiment. Life only comes from life, and if there was no life on earth to start with, then it is a conundrum of the ages.
So let us assume life on earth came from life in outer space (which strongly implies extra-terrestrials). Given the favorite "Big Bang" theory, I think atheists are faced with an even bigger problem. You believe that at one point the entire universe was compacted into one condensed orb of matter and energy, until it couldn't be compacted any more and instead exploded, thus creating the universe as we see it. If this is true, then we must also assume the conditions of all matter and energy compacted into one single space would be unsuitable for any form of life to exist. And if that is true, then where did life come from? Because life would have to come from the universe, created by the Big Bang that cannot support life, and come to earth.
Who knows? I certainly don't. Then again, this is all coming from a teenager's understanding of evolution and the Big Bang, which I'm sure most of you atheists would simply shake your heads at. Oh well.