Science insists that evolution has happened and may, very well, continue to happen. If evolution is good science, how can you fit the conflict between good and evil into the big picture? Do you suspend belief in science and it's proofs for evolution, i.e., natural selection, the fossil record, etc., and affirm your faith in the Bible's creation account and its concurrent 6,000 year age for the Earth? If you accept that Adam and Eve existed, and the Bible makes their creation very important to the future history of the human race, how do you account for evolution's suggestion that death existed before Adam and Eve sinned? These are not easy questions, but they should be addressed lest they continue to hound us for years.
Recently a possible solution started to take shape. Evil and it's close cousin, sin, existed from the very beginning of cosmic time. I'm not suggesting that there was never a time that evil did not exist, although theoretically it has always existed as an essential opposite of good and its close cousin, righteousness. If evil and sin existed before the fall, then how could Adam and Eve be punished, as well as their once-perfect world, if evil already existed before they sinned? Was the Adam and Eve experiment, if you will, another opportunity to see if free will would choose good instead of evil? How many other Adam and Eve experiments have there been? The universe is pretty old; its age numbers in billions of years. Has this tug of war between good and evil been going on for as many years?
In a related line of thinking, if evil theoretically could always exist as an alternative to good, would it make sense to prevent the possibility of evil rising again, if at some golden future event, evil is vanquished by divine agencies? Wouldn't that be as unjust as never allowing evil to exist the first time around?
The best our universe can ever hope for--realistically speaking--is to keep evil at bay. There will always be evil--albeit in its quiescent state--in the same way that all of the complimentary opposites must always exist. Left is incomplete without its direct opposite, right. Up and down must ever exist. Dark and light, as well. Good and evil, by their very nature, must always exist in some form or another. To think otherwise is impractical and incomplete.
Intelligent beings have at their disposal the option to bring about a universe where good and righteousness by the grace of God, triumph time and time again, over evil and sin, ad infinitum.