The methods used are popularly called Redaction Criticism, Redaktionsgeschichte, Kompositionsgeschichte or Redaktiontheologie -- a critical method for the study of biblical texts. They regard the author of the text as editor (redactor) of his or her source materials. Unlike its parent discipline, form criticism, redaction criticism does not look at the various parts of a narrative to discover the original genre; instead, it focuses on how the redactor has shaped and molded the narrative to express theological goals.(Wikipedia)Anyone who has digested the 'Book of Enoch' will note that that particular book wasn't actually written by Enoch himself, but is a fanciful compilation of Enoch's campfire stories. The book, mostly accurate in general if not in detail, is pretty much the oldest information our history has to offer, because, after all, Enoch was the fifth actual human on earth This is explained in the monograph, Earth is Mankind's Chrysalis,
Much of the biblical study of these observations was accomplished via redaction reconstruction, a method telling the observer which biblical verses of the bible were obviously redacted even prior to King James original 1611 compilation.
Material reconstructed from Biblical redaction by partisan Christian editors—in this case the Bible's book of Genesis—reveals a much different, more enlightening and, it's dared to suggest, even epiphanal view long kept hidden from those desirous of knowing the ways of God.
The task began for this observer in 1978, when confused by the bumpy and often misleading narrative of various Bible versions available to him, in order to understand the thought processes behind those writings, earnestly asked God Himself for clarification. Within short notice he found himself able to verify or discount the veracity of certain whole passages or individual verses -- able to see where much malicious thought had replaced them.
It was like discerning where a cities' firm foundation had been scooped out and replaced with sand.
The observer, only a man of the earth, cannot take any credit for himself other than that of having asked God for the ability, and of being receptive to the miracle. For to this day his keen heavenly discernment keeps him above all evil mechanizations, a gift given him by the generosity of God.