"Atheist" is a very generic term. Some of the first atheists back in antiquity could have believed life was never created as it always existed much the way they see it, so in their logic there was no need for a creator, because if life had always existed there was no necessity for one, thus arguing their case for not believing in God. Some may have even believed the earth was of an infinite age and had no beginning and therefore no intelligent creator. They could have believed the natural world had always existed rather like many theists arguing the eternal existence of their God. The first atheists would never have heard of Darwin or even Lamarck; so evolution was nowhere near as important to them as many compemporary atheists of today, like many modern day scientific theories would be to Charles Darwin. Back in antiquity they may have heard of Anaximander instead with his theories that all animal life evolved from the fish of the seas, but certainly not Darwin and looked on Anaximander's theories as being unproven speculation of their times.