Correction/Revision: The last paragraph of my prior post is now revised to say the following.
Note for the example the following. Genesis 32:28-29 records an angel as saying that Jacob's "name will no longer be called Jacob but Israel", but 2.5 chapters later, in Genesis 35:18, Genesis records God telling Jacob "no longer is your name to to be called Jacob, but Israel your name will become." Notice that in one case an angel is saying the name will be changed but that in another case God is saying it. Though these examples might not be a contradiction of each other, it is still odd that Jacob is being told that at two different times (once by angel and once by God). The latter part of Genesis 35:18 says "And he began to call his name Israel" yet verses 14, 22, 27, and 29 still say Jacob even though verse 21 says Israel, and 36:6 says Jacob instead of Israel. It is odd that chapter 35 keeps switching back and forth from the use of the name Jacob to the name Israel, and 37:1-2 says Jacob instead of Israel, but the idea of somewhat conflicting documentary sources being combined makes sense of this.
I remember that at least one time when I was an active JW I was perplexed why the book of Genesis kept switching back and forth in its use of the names Jacob and Israel for the some person - even after the portion of the narrative which said the name change by God took effect. Back then I didn't know of the documentary hypothesis.