Mankind’s knowledge ebbs and flows.  Galileo got into trouble with the “learned” men of his day for saying that the earth moved.  When he was called before the Inquisition in 1633 for saying that the earth moved around the sun, instead of vice versa, he was caused to recant his statements.  Following his recantation he reputedly mumbled under his breath, “And yet it moves!”  The report of that event is probably not accurate, but it is an historical fact that his theories of the earth’s movement were the opposite of the then-prevailing belief.

Contrast the knowledge of the Catholic inquisitors in 1633 with Mormon’s statement of fact written prior to 384 A.D.:  “…for surely it is the earth that moveth and not the sun.”  (Hel. 12:15).

Another example of lost knowledge also comes from the Book of Mormon.  Alma 46:40 says, “And there were some who died with fevers, which at some seasons of the year were very frequent in the land—but not so much so with fevers, because of the excellent qualities of the many plants and roots which God had prepared to remove the cause of diseases, to which men were subject by the nature of the climate.”

I think what that verse is saying is that the Book of Mormon peoples lived in a tropical climate where malaria and other such diseases were a problem.  The problem didn’t loom as large then as it did in more modern times because the people had effective herbal remedies of which we still have no knowledge.

The whole Book of Mormon is lost knowledge.  It is the religious history of a branch of the House of Israel of which the world had no knowledge.

The world has very little knowledge about the Jaredites.

The world is also unaware that one of the sons of Zedekiah survived what was considered to be the complete obliteration of that family by the Babylonians.