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Question: Does the use of tribal affiliation in the Book of Mormon imply a genetic link between the members?
The Book of Mormon text makes it clear that tribal designation has a political role, not a genetic one
The Book of Mormon text makes it clear that tribal designation has a political role, not a genetic one. Individuals switch tribal designation as their religious and political loyalties shift. The critics view of them as strictly genetic categories cannot be maintained beyond the first few years of settlement.
Contrary to these claims, the Book of Mormon is clear that tribal designation is a political, not genetic matter.
On author noted:
An analysis of the terminology applied to peoples in the Book of Mormon could reveal useful information on this subject. This is not the place to do that fully, but the approach can be sketched and some of the results anticipated. References to the key people of the record vary: (1) "Nephite(s)" or "the Nephites" occurs 339 times; (2) "people of the Nephites," 18 times; (3) "people of Nephi," 4 times; (4) "children of Nephi," twice, and (5) "descendants of Nephi," twice. Usage of the second and third expressions gives us something to ponder about the composition of the people referred to.
The meaning of the first expression is made clear early by Jacob when he says, "those who are friendly to Nephi I shall call Nephites." Then he continues the definition in an interesting way: ". . . or the people of Nephi, according to the reigns of the kings" (Jacob 1:14). A few lines earlier Jacob had reported that when Nephi anticipated his own death, he had designated "a [successor] king and a ruler over his people . . . according to the reigns of the kings. . . . And whoso should reign in his stead were called by the people, second Nephi, third Nephi, and so forth, according to the reigns of the kings; and thus they were called by the people, let them be of whatever [personal] name they would" (Jacob 1:9, 11). Jacob here makes clear that his definition of "Nephites, or the people of Nephi" hinges on political allegiance to a king, a king who always bore the title "Nephi." This definition does not depend at all on whether "Nephites" were or were not literal descendants from Nephi, nor whether they had Sam, Jacob, Joseph, or Zoram, the founding fathers of the group, among their ancestors. In fact Jacob's terminology may refer to the original father Nephi only indirectly. What he says in verse 11, where the term "Nephites" is first used, is that those classified under that term were simply all who were ruled by the existing monarch, the current "Nephi." No reason is evident to me to believe that in the 338 usages after Jacob begins the practice that "Nephite(s)" means anything else. It is essentially a sociopolitical, not an ethnic or linguistic, label.
Cases where the text reports that political allegiance changed are consistent with this notion. Thus the children who had been fathered, then abandoned, by the renegade priests of Noah chose to "be numbered among those who were called Nephites" (Mosiah 25:12). That is, when they came under the sovereignty of the current head of the Nephite government, they both gave their allegiance to him and changed their group label to "Nephites." In a parallel case earlier, "all the people of Zarahemla were numbered with the Nephites, and this because the kingdom had been conferred upon none but those who were descendants of Nephi" (Mosiah 25:13). Conversely, when Amlici and his followers rebelled against Nephite rule and "did consecrate Amlici to be their king," they took a unique group name to mark the political rebellion, "being called Amlicites" (Alma 2:9). Meanwhile "the remainder"—those loyal to Alma, the continuing official ruler—"were [still] called Nephites" (Mosiah 25:11). Again, when the Zoramites transferred allegiance from the Nephite government to the Lamanite side, they "became Lamanites" (Alma 43:4, 6). We see, then, that the Nephites constituted those governed by the ruling "Nephi," who was always a direct descendant of the original Nephi. But the label does not of itself convey information about the ethnic, linguistic, or physical characteristics or origin of those called Nephites.
It is true that the name "Nephites" sometimes connotes those who shared culture, religion, and ethnicity or biology.5 But every rule-of-thumb we construct that treats the Nephites as a thoroughly homogeneous unit ends up violated by details in the text. Variety shows through the common label, culturally (e.g., Mosiah 7:15; Alma 8:11–12), religiously (e.g., Mosiah 26:4–5 and 27:1; Alma 8:11), linguistically (e.g., Omni 1:17–18), and biologically (e.g., Alma 3:17, note the statement concerning Nephi's seed "and whomsoever shall be called thy seed"; Alma 55:4). "Nephites" should then be read as the generic name designating the nation (see Alma 9:20) ideally unified in a political structure headed by one direct descendant of Nephi at a time. 
To see citations to the critical sources for these claims, click here
- John L. Sorenson, "When Lehi's Party Arrived in the Land Did They Find Others There?," Journal of Book of Mormon Studies 1/1 (1992): 1–34. wiki