The people of Zarahemla had become very numerous, but they had been subjected to civil war and periods of self-destruction like the Lamanites and the Nephites had. Their language had also become corrupted because they had brought no records with them. Their religion had also become corrupted, and they even denied the existence of their Creator.
Originally, both the Nephites and the people of Zarahemla had spoken Hebrew. The Nephites kept their language relatively stable because they were a record-keeping people. The people of Zarahemla, however, did not take any records with them and after nearly 400 years, their language had changed so much that the people of Mosiah could not understand them.
To remedy this situation, Mosiah taught them the Hebrew language. Once the two people could communicate together, the king of the people of Zarahemla gave Mosiah his genealogy from memory. This phenomenon of having a people memorize their genealogy is found among a number of ancient people.
Now it turned out that before long the people of Mosiah and the people of Zarahemla became one people. They combined and elected a king. The person they elected, amazingly, turned out to be Mosiah. This was a remarkable development in which an invading people were welcomed by the original inhabitants of a country and then they voluntarily voted to make one of the invaders their king.
The people of Zarahemla were apparently of Jewish extraction; at least they had come out of Jerusalem and brought with them the only surviving son of king Zedekiah -- a direct descendant of king David.2 So from here on many of these people will constitute a mixture of Manasseh through Lehi, of Ephraim through Ishmael, and Judah through the people of Zarahemla. Some of them will even carry in their veins the royal blood of king David through Mulek.3