Atheists, how do you explain this?

I would say your limited capacity to imagine possibilities has biased your conclusions. Take a look at the article listed in the sources section and then tell me you find it difficult to believe that abiogenesis is not possible given the proximity of elements, the energy needed, and billions of years worth of rolling the dice. Are you really sure nature is incapable of rolling boxcars? I do not think you give nature the credit she is due.