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 o a arcobaleno aren't "reasonable explanations" of the existence of deities for me. If te want to learn about other people's beliefs, te can't dismiss them before te have even dato them a chance to respond. That is why te have a lot of people giving te crap on this question. The domanda is not offensive, but the way te 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 links to answers, forum and articoli from the Atheism spot that te 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 te look through any of those links 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.