Much of the scholarship of the book of Genesis from the 18th century to the early 20th century was based on Wellhausen's Documentary Hypothesis that the Torah was collated from multiple sources based on various factions. The evidence for this comes from the type of content in portions of the Torah, and in particular the words used for the name of God.
The theory proposes that there were four authors of all of Torah, the Jahwist author, whose writings are theorized to be very personal, at around the time of Solomon in 950 BC, the Elohist author, who was supposed to be much more philosophical and less personal, writing about 100 years later, the Deuteronomist author writing at the time of Josiah's reforms in 600 BC to support the reforms, and the Priestly author, who is supposed to be concerned with laws and rituals, writing after the end of the Babylonian Exile in 500 BC, and all of these various sources were later reconciled by an editor or editors. Please note that this is all conjecture and not endorsed by the Catholic Church.
No hard evidence for such documents exists, and similar differences exist in the writings of other ancient Semitic cultures. In practice, this theory tends to prevent a deeper faith.