Is it true that the Hebrews descended from a lesser Canaanite tribe?

No, The Bible says that Abraham, the original ancestor of the Hebrews, came from Ur of the Chaldees.

Genesis 11:31 And Terah took Abram his son, and Lot the son of Haran his son's son, and Sarai his daughter in law, his son Abram's wife; and they went forth with them from Ur of the Chaldees, to go into the land of Canaan; and they came unto Haran, and dwelt there.

Answer:

The previous answer is traditional, but probably not factual. There was a relationship because the language of Old Canaanite is just a dialect of Hebrew. New scholarship suggests that the Hebrew may in fact have been Canaanites.