There is a common argument posited by many Christians that, since the Bible isn't a "science book and doesn't really say anything about how old the earth is and never used the word 'evolution,' this whole thing doesn't really matter that much." While it may be true that the Bible doesn't use the word "evolution" and is definitely not a science text book, that does NOT equate to the Bible being inconsistent with scientific observation and it certainly doesn't mean that we can't use Biblical information to support those scientific observations.
Here's why - the Bible either is the Book we claim it is, or it isn't. The Bible is either the unerring and absolutely true account of God's activity in the early history of the Israelites, or it isn't. The Bible either accurately portrays Christ's life and ministry on earth, or it doesn't. If the Bible isn't accurate and isn't the authoritarian Word of God, then how can we know what we should "believe" and what we shouldn't?
There are Christians who believe that the Genesis account of creation is not meant to be taken literally. Why? Because for some it is too fantastic to believe. For others, "science" is not consistent with a literal interpretation of Genesis. There are other reasons, too, but the ultimate foundation is because their humanly observations and knowledge is not consistent with a literal interpretation.
Even though the language used in the earliest accounts of Genesis was written using a format that Hebrews recognize as being "historical," people choose to believe it is not meant to really mean literal days and is what God inspired Moses to write. Even though the word used in Genesis for "day" - yom - means a literal 24 hour period of time AND every other place "yom" is used in the Bible it is used to indicate a literal 24 hour period of time AND even though there are Hebrew words to mean "day" as in "back in the day" or "one day I will do that" and yet those words for the "nebulous-concept-of-the-word-day" are NOT used in Genesis when describing the "creation days," many people believe that the Genesis "day" is not a literal 24 hour period of time.
There are some very devout and knowledgable Christians who do not believe that the Noah story is literal or that the Jonah story is literal, largely because it is either "too hard to believe" or they believe that science contradicts those beliefs, or both (and other reasons, too). And yet, these same very devout Christians believe that Jesus Christ was crucified for their sins, died, was in the earth for three days and then rose again with life such that his previously dead human form was once again inhabited by His Heavenly Spirit.
Now, back to my original point. The point is, how is it that human beings, sinful, prone to making mistakes and being prideful, can believe the "Jesus Story" but not the other stuff (or selected stories of the "other stuff)? If God has the power to raise people from the dead, which He did at least 8 individual times, including Lazarus, after being dead for "four days," (John 11:39, KJV: Jesus said, Take ye away the stone. Martha, the sister of him that was dead, saith unto him, Lord, by this time he stinketh: for he hath been dead four days) why wouldn't He be able to create man from dirt or send a world wide flood or keep a man alive in the belly of a great fish? Either our Lord is a being with limitless power (really, only limited by our small human minds), or He isn't. Either His word is true - all of it - or it isn't. It seems like it doesn't make any kind of sense to believe the Jesus story is real but everything else (or selected bits and pieces) is just allegorical. What gives a human the ability to say, "Man, all that other Bible stuff isn't real, they are just stories, but that Jesus stuff, now that is real!"? I just don't get that.
Either the Bible is 100% truth (God can't lie and if He wrote stuff as literal history, then it is....just as it is clear that He inspired authors to write things that are clearly poetic or allegorical), or it isn't. We can't choose what we think sounds good and what we think is "real" because all that does is end up undermining the authority of Scripture, causing a person to be standing on the sand. If we choose to not believe the Genesis account (or the Noah story, or the marching-around-the-city-seven-times-and-it-fell story, etc) but do believe the Jesus story, what is the foundation for that faith?