General questions about the history in Genesis, chapters 1-11

The first few chapters of the Bible, Genesis 1-11, deal with the history of world before Abraham. Beginning with the creation of the world, these chapters present human history from the birth of Adam to God's covenant with Abraham. They include some of the most well-known biblical stories - man in the Garden of Eden, Cain's murder of Abel, the great flood in the times of Noah, and the Tower of Babel.

No doubt these stories are all quite fascinating. But what is their point? Why include the story of early man in the Bible at all? How does this area of historic data fit in with the rest of the focus of the Bible?

Moreover, why these particular stories and none other? To be sure, all history is necessarily selective and sketchy. The story of man cannot be captured in a book. But one expects a book to have a rationale for the selection and inclusion of material. Surely, many more events of interest happened during the roughly 2000-year time-period covered by the first eleven chapters of Genesis. Are the events chosen by the Bible just a random collection of "interesting" events with no clear focus, or do they convey an overarching message fundamental to an understanding of the Bible?