Let's not confuse MYTHOLOGY with RELIGION
for starters.
Mythology is like a culture creating 'Gods' or 'Soapie Stars' (or Super Heroes as they do in the USA in their 'Cinema' temples) - both entertaining and as fictional characters (although based upon people of the past most likely), to help convey a 'moral' understanding or human learning. Mythology is all that Psychology had dreamed of.
Religion was first created by the Jews. They took the invention of Writing (by the Sumerians upon the Temple of Ur via the inspiration of Sin <aka Moon/Luna> and hence the word 'Sin-Ur' <sinner>) and used it to 'immortalise' their Family Tree - the Jews. By doing so, they became 'exiled' from the 'nature' of everything else as a Bloodline (started by two Jews: Adam & Eve), having sold their souls to 'Writing' and eventually - the Book.
Thus - their future was guaranteed and their past, immortalised ...like Gods.
Now I could go on and elaborate further, but for the quick response to the question.
Atheism came about as a Rebellion against all things 'Religious' (you know - the invention that helped discover the New Worlds, because Science couldn't get its crap together yet
) and originally ATHIESM didn't really know what it was (which is why the question still remains "What is Atheism?"
...like a 'tradition') - but it knew that it was totally
ANTI
(against) RELIGIOUS.
These days now though - Atheism is finding itself very 'Pro' as in Pro-Science and basically it is finding its cultural friends with Science, Media and Café Latte Hipsters in black skivys. Celebrities are now the main 'personality' of an Atheist.
...so, for my last input.
Atheist: Someone who comes from the Region of Oceania (Science) and is Anti someone from the Middle-East (Religion).
Now remember: BOTH Creationism & Evolution are right.
Who said there has to be only 'one' right answer?