Jerry Ainsworth notes that in the lowlands of Mesoamerica, king Mosiah discovered the people of Zarahemla--the Mulekites. These Mulekites then united with the Nephites (see Omni 1:19), both groups being of Hebrew origin. Maya scholars Linda Schele and Mary Ellen Miller discuss what appears to be the effects of that merger:
The lowland Maya dramatically and suddenly (in the sense of archaeological time) reversed their attitudes toward public art in the second half of the Late Pre-classic period. Sometime between 200 and 50 B.C., the lowland Maya exploded with a massive building program that altered forever their landscape. Remains of this construction have been found in Tikal, Uaxactun and El Mirador in Guatemala, and at Cerros and Lamanai in northern Belize.
Why did such a transformation occur? Why was it so sudden, if not in its cause, unquestionably in its effect? (Blood of Kings, p. 105)
It is certain something happened to the lowland "Maya" (the Mulekites) after 200 B.C. that dramatically changed their society. The obvious answer to readers of the Book of Mormon is that the migrating Nephites, who were highly civilized, interfaced with the Mulekites, who had lost much of their Hebrew culture and religion.
Speaking of a new epoch in Mayan history that commenced in 236 B.C., Sylvanus Morley observes in The Ancient Maya that "with the introduction of the calendar, chronology, and hieroglyphic writings, all three of priestly invention, Maya religion underwent important modification." This statement makes most sense against the backdrop of king Mosiah's role as the Nephites' priest-king and his new role as leader of the Nephite-Mulekite coalition.
Morley again notes that "the Maya probably developed their agricultural system, upon which their whole civilization was based, in the Guatemala highlands . . .[whereas] their highly specialized culture originated in the interior drainage basin and reached its most brilliant esthetic expression in the lush Usumacinta Valley" [Jerry L. Ainsworth, The Lives and Travels of Mormon and Moroni, pp. 88-89]