Brant A. Gardner argues the Jaredites probably were polygamists based on details found in Ether 6:14–16.
Brant A. Gardner, Second Witness: Analytical and Contextual Commentary on the Book of Mormon, 6vols. (Salt Lake City: Kofford Books, 2007), 6:230
The Jaredite party apparently consisted of at least forty-four adults. The "twenty and two souls" (plus Jared and the brother of Jared) were, almost certainly, the men, each of whom likely had a wife. They had children before leaving the tower area; certainly others would have been born en route. The brother of Jared has twelve children. While twelve children are not unknown or even unusual in monogamous relationships, the later biblical precedent of Jacob's twelve sons suggests the possibility of plural wives. Assuming that this is so, a probable maximum number would be twenty-four adult males, perhaps forty-eight adult females, and 288 children. Thus, a probable maximum population in the New World would be 360 people, a reasonably large hamlet. These numbers, however, are a maximum, and the actual party was probably smaller if not every man had two wives or fewer children than twelve.