We have always said that when people reject Genesis, it leads to unbelief in the rest of the Bible. This is because Genesis is foundational to the rest of the Bible. If Genesis is not literal, then Christian doctrine cannot stand. Even the humanists understand the importance of Christ as redeemer dying for our sins. From the viewpoint of anthropology it is exceedingly unlikely that there was a First Man and Woman.
Human beings are the result of evolution, and shaped by natural selection.
Self-centeredness and aggression were essential at every stage of evolution. Since the meaning of anything is dependent on its origin, if the origin is myth, then anyone can determine the meaning. This is the point that many church leaders seem to miss. If the events of Genesis are not literally true, then sin and marriage, etc., can be defined in any way one decides. This is exactly what Montefiore does.