While Jews and Christians have traditionally believed that Moses was the primary author of the Pentateuch, some biblical scholars today reject that belief. Instead, these scholars believe that the Pentateuch was written over several centuries by several different authors and not finally compiled into its final form until just a few hundred years before Jesus was born.
Daniel I. Block, in the Apologetics Study Bible, provides more detail. Block writes that biblical scholars in the mid-nineteenth century began to question the traditional authorship of Moses.
The questioning began early with doubts whether Moses recorded his own death and burial (Dt 34), knew of a place in northern Israel called Dan (Gn 14: 14; cp. Jos 19: 47; Jdg 18: 28-29), or referred to the conquest of Canaan as having occurred in the past (Dt 2: 12). Thus scholars developed an alternative explanation for the origin of the Pentateuch known as the Documentary Hypothesis.
According to the classical form of the theory, the Pentateuch is the product of a long and complex literary evolution, specifically incorporating at least four major literary strands composed independently over several centuries and not combined in the present form until the time of Ezra (fifth century B.C.). These sources are identified as J, E, D, and P.
J represents a ninth century B.C. (c. 850) document that originated in Judah, distinguished by its preference for the name Yahweh (Jehovah, hence the “J”). The E source preferred the divine title Elohim, and theoretically was composed in Israel in the eighth century B.C. The D stands for Deuteronomy, supposedly written around 621 B.C. to lend support to Josiah’s reforms. The priestly document, P, supposedly was composed c. 500 B.C. by priests seeking to preserve their own version of Israel’s history.
According to the theory, these sources were compiled and combined in the middle of the fifth century B.C. Nehemiah 8 recounts the moment when Ezra publicly read the Pentateuch as a unit for the first time. . . .
Variations of the Documentary Hypothesis prevailed for more than a century. However, due to advances in literary studies, today the state of pentateuchal scholarship is confused, with new theories or radical modifications appearing often.
There are significant problems with the Documentary Hypothesis and its off-shoots, as noted by many conservative scholars. Those will be addressed in a subsequent post. For now, it is important to know that this basic theory of the composition of the Pentateuch is still very influential among many biblical scholars.