Of all the material Jacob could have adopted as his prophecy, his selection of Zenos' allegory of the Olive Tree is telling. The account is a journey through various dispensations of the Gospel, tracking a bloodline of chosen people. To Jacob's credit, he realized the work of salvation was devoted primarily to rescuing the descendants of a chosen line beginning with Abraham.
The allegory is a family story. The use of the Olive tree is a deliberate symbol of a family, and of the tree whose value was beyond question in the culture from which the allegory sprung. To understand the story, it is necessary to settle on meanings.
The tree is a family line belonging to the "house of Israel." (Jacob 5: 3.) The work of the Lord of the vineyard and his fellow laborers is designed to cause the chosen family line to produce fruit worthy of preservation. The "fruit" is people, or more correctly, children raised in righteousness who comprehend and accept the Gospel and abide by its teachings. The name "Israel" is the new name given to Jacob. Jacob was renamed by the Lord because the Lord took him into His own family. Naming signifies Fatherhood over Jacob, and the name Israel signifies the Family of God.
Not every descendant of Jacob is also a descendant of Israel. Blood is one thing, adoption into the Family of God is another. The allegory should be read with the proper context. It is about preserving the Family of Israel, or in other words, the Family of God.
To correct and instruct the chosen family, it was necessary for the Lord of the vineyard, in a desperate attempt to cause the family to produce fruit worthy of preservation, to disburse the children, scatter them throughout the vineyard, graft wild branches into the roots and tame branches into wild roots. In one sense the failure of the chosen family is to the world's great blessing. In the end, the world overcomes the chosen family and all those grafted into it, and in the final effort the work returns to the original roots and the original branches in a desperate final attempt to salvage something from the vineyard before it is burned.
Choosing this allegory as the great central theme of Jacob's book shows his comprehension of sacred history and prophecy, and his knowledge of the future. Unlike Nephi, whose muse was Isaiah, the fully mature prophet Jacob turned to Zenos to act as "second witness" to his prophecy. We have in Jacob Chapter 5 the great explanation of how we got where we are today, and what will unfold before the Lord's return to burn the vineyard. It is odd we spend so little time with the material. It is the central theme of all man's history (from God's point of view).
The family is scattered into several different parts of the vineyard:
First, the location of the original tree.
Second, an undisclosed number of "nethermost parts of the vineyard." (Verse 14.)
Third, a "poorest spot." (Verse 21.)
Fourth, a "poorer spot than the first." (Verse 23.)
Fifth, a "good spot." (Verse 25.)
However, there is no attempt to quantify the number of spots because the allegory is intended to convey meaning apart from numbers. You can cross check the other prophecies from Nephi (2 Ne. 29: 3) and Christ (3 Ne. 17: 4) and find there is no definitive number given of how many separate groups are included in the "nethermost parts of the vineyard" where Israel was scattered.
What should leap out to you from this allegory is the nature of the Gospel and God's work among mankind. It was and is related to preserving a single family line. The "God of Israel" is concerned with preserving the chosen line of heirs. The Gospel was and is a family matter, and the target of the Lord's work is now and always has been the preservation of a specific group He intends to preserve.
This is an image we have trouble with in our current multiculturalism. We tend to view all mankind as the beneficiaries of God's plans to save mankind. They are to some extent. After all, He provides the sun and rain to everyone regardless of their ethnicity. (Matt. 5: 45.) And every people are given according to His mercy some portion of truth calculated to benefit them. (Alma 29: 8.) However, Zenos and Jacob agree the Lord's primary effort has been directed at preserving one family, and the world has been the incidental beneficiaries of this global effort to preserve them.
We will look at the history of this family as told through the allegory of the Olive tree.