For much of the 20th century most scholars agreed that the five books of the Pentateuch—Genesis, Exodus, Leviticus, Numbers and Deuteronomy—came from four sources, the Yahwist, the Elohist, the Deuteronomist and the Priestly source, each telling the same basic story, and joined together by various editors.
Since the 1970s there has been a revolution in scholarship: the Elohist
source is now widely regarded as no more than a variation on the
Yahwist, while the Priestly source is increasingly seen not as a
document but as a body of revisions and expansions to the Yahwist (or
"non-Priestly") material. (The Deuteronomistic source does not appear in
Examples of repeated and duplicate stories are used to identify the
separate sources. In Genesis these include three different accounts of a
Patriarch claiming that his wife was his sister, the two creation
stories, and the two versions of Abraham sending Hagar and Ishmael into
This leaves the question of when these works were created. Scholars
in the first half of the 20th century came to the conclusion that the
Yahwist was produced in the monarchic period, specifically at the court
of Solomon, 10th century BC, and the Priestly work in the middle of the 5th century BC (the author was even identified as Ezra), but more recent thinking is that the Yahwist was written either just before or during the Babylonian exile of the 6th century BC, and the Priestly final edition was made late in the Exilic period or soon after.
As for why the book was created, a theory which has gained
considerable interest, although still controversial is "Persian imperial
authorisation". This proposes that the Persians of the Achaemenid Empire,
after their conquest of Babylon in 539 BC, agreed to grant Jerusalem a
large measure of local autonomy within the empire, but required the
local authorities to produce a single law code accepted by the entire
community. The two powerful groups making up the community—the priestly
families who controlled the Temple and who traced their origin
to Moses and the wilderness wanderings, and the major landowning
families who made up the "elders" and who traced their own origins to
Abraham, who had "given" them the land—were in conflict over many
issues, and each had its own "history of origins", but the Persian
promise of greatly increased local autonomy for all provided a powerful
incentive to cooperate in producing a single text.
perhaps best seen as an example of "antiquarian history", a type of
literature telling of the first appearance of humans, the stories of
ancestors and heroes, and the origins of culture, cities and so forth.
The most notable examples are found in the work of Greek historians of
the 6th century BC: their intention was to connect notable families of
their own day to a distant and heroic past, and in doing so they did not
distinguish between myth, legend, and facts. Professor Jean-Louis Ska of the Pontifical Biblical Institute calls the basic rule of the antiquarian historian the "law of conservation": everything old is valuable, nothing is eliminated.
Ska also points out the purpose behind such antiquarian histories:
antiquity is needed to prove the worth of Israel's traditions to the
nations (the neighbours of the Jews in early Persian Palestine), and to
reconcile and unite the various factions within Israel itself.