Ok, TWD, explain this: God made Adam and Eve. They had only two kids, who were both boys, right? Provided they didn't do their mother, where did all the other humans come from?
That "Bible" book you are reading - it may be full of nice and not-so-nice stories, but it was never intended to be taken literally. Some of its content may have historic background (e.g. Jesus likely existed), but other parts are just made up (e.g. the story around Jesus' birth, which was added much later). Many parts also suffered from translation errors, especially some of the numbers.
Oh, and didn't Jesus die for our sins? How come the world didn't change back into what it was before "The Fall"? Cognitive dissonance FTW!