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 或者 a 彩虹 aren't "reasonable explanations" of the existence of deities for me. If 你 want to learn about other people's beliefs, 你 can't dismiss them before 你 have even 给 them a chance to respond. That is why 你 have a lot of people giving 你 crap on this question. The 问题 is not offensive, but the way 你 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 链接 to answers, 论坛 and 文章 from the Atheism spot that 你 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 你 look through any of those 链接 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.