BS”D
Wolf:
Remember that the only concern is if there are large pieces of land transfered.
Since land can not be consolidated by one individual (due to yovel returning all purchased land), each time there is a new generation, the land holdings get diluted. If a diluted portion of land gets transfered to another shevet, it is not such a big deal, since it is small.
The problem begins when the land does get consolidated through yerusha to persons other then sons. This happened during Pilegesh B’Giva, when most of Binyamin was wiped out. The land of Binyamin was the yerasha of the remaining 600 members of the shevet (via them being cousins, through the grandfathers). Each member now had a very large piece of land.
Therefore, at that time, they made a Takana to minimize the transfer of land out of the shevet. For example, they were careful not to marry outside the shevet if they got the yerusha (Rashbam BB 116B), and they were also M’Taken other methods to keep the yerusha within the male line (see Gemorah & Rashbam there).
Please feel free to ask any additional questions, or if you don’t understand, please be more specific, and I will (Bezras Hashem) try to help.
G@W