the old testament  was for the fulfill of the fleashly ways and how the christ would come to this earth now the new testament explans that the Christ at his resurrection had  fulfill the law of the flesh and now is in spirit and this is what the new testament is for to help us come out of the flesh and in to the spirit of the Christ by the Holy Spirit, the new testament helps us become spiritual has we live in the flesh on this earth 

If you read down to  16 you can read that Cain move to the land of Nod so we know from scribture that places were named after people so their had to be people on the earth at that time, remember the Biblie dosn't tell us evey detail that was happening on the earth, the Bible is here to teach us how to build our Godly charectors so their are only sertent stories that are told to us that will help us build the charector that the story is talking about.