First of all there were many civilizations before christ. Many cyclical cataclysms had already happened.
Secondly not everything in bible is true. It has been doctored heavily after jesus's death. The changes were of two types.
1st type were the direct changes. Changes made by opposing or denying what was the message of God. These changes are very few in count. Less than what you can count in your hand.
2nd types are the use of metaphors and stories. Many direct, literal messages were replaced with metaphors and stories. These changes comprises more than a tenth of bible. The reasoning behind these changes were given that these will help illiterates and poor intellect people to understand God's word. Another reasoning given was that these are tests and only the ones with pure souls will be able to understand the true meaning. Reality is that these changes were made to be double meaning. An average person will just read the bible and will almost always reach the 'artificial' conclusion. While thhose who made changes have a 'codebook' and with that they can decrypt the true message anytime.

I cannot reveal any of these changes as that will be violation of rule one. But there lies a hope in the fact that the descendants of those who made these changes, the lineages, they still have all the details about these changes. Complete documentation. If they want they can release it anytime. If you are willing to pay the right price or if you have got enough leverage.