First of all, as others have already pointed out, evolution may not be a "reasonable explanation" for you, but it is for other people who have different belief systems. Just like the bible または a 虹 aren't "reasonable explanations" of the existence of deities for me. If あなた want to learn about other people's beliefs, あなた can't dismiss them before あなた have even 与えられた them a chance to respond. That is why あなた have a lot of people giving あなた crap on this question. The 質問 is not offensive, but the way あなた have asked it is.
Secondly, there are lots of places around here where Atheists and people of other religions have discussed this topic respectfully. Here are some リンク to answers, フォーラム and 記事 from the Atheism spot that あなた might want to take a look at:
link link link link link link (we also have a couple of 'Ask A Christian' forms)
link link link If あなた look through any of those リンク you'll see that Atheists believe in a wide range of things for a wide range of reasons. We, for the most part, don't mind explaining our beliefs to people who want to learn about them, but we do require respectful debate.