It is impossible to reject the historicity of the book of Genesis without repudiating the authority of the entire Bible. If Genesis is not true, then neither are the testimonies of those prophets and apostles who believed it was true. In the Old Testament, for example, Adam is mentioned in Deuteronomy, Job, and 1 Chronicles, while Noah is mentioned in 1 Chronicles, Isaiah, and Ezekiel. There are at least 100 quotations or direct references to Genesis 1-11 in the New Testament. Furthermore, every one of those eleven chapters is alluded to in the New Testament, and every one of the New Testament authors refers somewhere in his writings to Genesis 1-11.
My two cents
Wow, that was an action-packed and concise defence of the historicity of Genesis. I had probably assumed these points by implication, but this solidifies it and reinforces the internal consistency of the Biblical books.
When the facts are laid out like this, it shows the flimsiness of believing that Genesis (especially the first 11 chapters) were just an allegory. More to the point, it shows how those who keen on fitting evolution/old earth creation with Biblical revelation are forced to squeeze the plain meaning of the Bible like it were a tube of toothpaste.
Snelling, A.A. (2009). Genesis: Real, Reliable, Historical. Available: http://www.icr.org/article/4824/. Last accessed 13th Sep 2013.