This doctrine is taken for granted by latter-day saints. Search the record of Genesis! You will not find this doctrine taught in Genesis or anywhere else in the Bible. The implications of a different interpretation are enormous. Many Christian denominations believe that Adam and Eve could procreate prior to partaking of the forbidden fruit but that they didn’t. According to this doctrine, without their transgression, all of humanity would have been born into the paradise of the Garden of Eden. They conclude that the Fall of Adam forces all of mankind to live in a dark and dreary world instead of paradise.
This is where our doctrine differs. Thanks to Lehi, and other sources, we understand that they could not have children in their state of innocence. In fact, the entire plan of salvation would be spoiled if they had never partaken of the fruit. If they hadn’t, we would all still be in the pre-mortal existence while Adam and Eve remained in the Garden renaming the animals. Adam’s decision, prompted by the wise counsel of his wife, made it possible for all mankind to experience mortality and learn of the opposition in all things that Lehi spoke of. It was only in this way that they could become as God, knowing good and evil.
Joseph Fielding Smith
“ Adam and Eve therefore did the very thing that the Lord intended them to do…The Lord said to Adam that if he wished to remain in the garden, then he was not to eat the fruit, but if he desired to eat it and partake of death he was at liberty to do so. So really it was not in the true sense a transgression of a divine commandment….It was the divine plan from the very beginning that man should be placed on the earth and be subject to mortal conditions and pass through a probationary state as explained in the Book of Mormon.” (Answers to Gospel Questions, vol. 4, pp. 79-82 as taken from Latter-day Commentary on the Book of Mormon compiled by K. Douglas Bassett, p.92)