Those who have studied Mormonism’s history have seen that much of the Book of Mormon was written largely in part thanks to other sources that were available to Joseph Smith at the time he lived.
The two most notable examples are Joseph Smith’s plagiarism of the King James Bible, and Joseph Smith’s not-so-unique tales of native American Indians being ancestors of Israelites. The former was the standard translation of the Bible used in America at that time, and the latter was a popular notion advanced in numerous books during Joseph Smith’s time.
Even Mormons (including LDS general authority member and apologist B.H. Roberts) have had to concede the uncanny similarities between the Book of Mormon and other works of men available to Joseph Smith at the time.
In fact, there’s been much discussion about writings by Solomon Spaulding and Ethan Smith which are eerily similar to that of the Book of Mormon and predate the Book of Mormon.
You can read more on Solomon Spaulding’s manuscript here, and view the numerous similarities between Ethan Smith’s work and Joseph Smith’s Book of Mormon here.

But the Indians-are-Hebrews stories aren’t the only tales that were circulating during Joseph Smith’s time
There is another Mormon teaching that was espoused by early Mormon leaders that–like the Indian/Hebrew theory–was also not original to Mormonism. I’m speaking of the Mormon teaching that the moon was inhabited by men.
Oliver B. Huntington, who was a close associate of Joseph Smith and remained a faithful Mormon his whole life, said:
Astronomers and philosophers have, from time almost immemorial until very recently, asserted that the moon was uninhabited, that it had no atmosphere, etc. But recent discoveries, through the means of powerful telescopes, have given scientists a doubt or two upon the old theory. Nearly all the great discoveries of men in the last half century have, in one way or another, either directly or indirectly, contributed to prove Joseph Smith to be a prophet. As far back as 1837, I know that he said the moon was inhabited by men and women the same as this earth, and that they lived to a greater age than we do, that they live generally to near the age of a 1000 years. He described the men as averaging near six feet in height, and dressing quite uniformly in something near the Quaker style. In my Patriarchal blessing, given by the father of Joseph the Prophet, in Kirtland, 1837, I was told that I should preach the gospel before I was 21 years of age; that I should preach the gospel to the inhabitants upon the islands of the sea, and–to the inhabitants of the moon, even the planet you can now behold with your eyes. Young Woman’s Journal, Volume 3, pages 263-264, 1892
Huntington also said the following of Joseph Smith’s teaching regarding moon people:
The inhabitants of the moon are more of a uniform size than the inhabitants of the earth, being about 6 feet in height. They dress very much like the quaker style and are quite general in style, or fashion of dress. They live to be very old; coming generally, near a thousand years.” This is the description of them as given by Joseph the Seer, and he could “see” whatever he asked the father in the name of Jesus to see. The Journal of Oliver B. Huntington, Volume 3, Page 166
William A. Linn had this to say about Martin Harris, one of the three Witnesses to the Book of Mormon:
Daniel Hendrix relates that as he and [Martin] Harris were riding to the village one evening, and he remarked on the beauty of the moon, Harris replied that if his companion could only see it as he had, he might well call it beautiful, explaining that he had actually visited the moon, and added that it “was only the faithful who were permitted to visit celestial regions.” William A. Linn, The Story of the Mormons, Page 35, 1902
Of, course, not to be outdone by all the grandiose claims, Mormon Prophet Brigham Young went even farther by alleging that there are solar inhabitants as well:
We are called ignorant; so we are: but what of it? Are not all ignorant? I rather think so. Who can tell us of the inhabitants of this little planet that shines of an evening, called the moon? When we view its face we may see what is termed “the man in the moon,” and what some philosophers declare are the shadows of mountains. But these sayings are very vague, and amount to nothing; and when you inquire about the inhabitants of that sphere you find that the most learned are as ignorant in regard to them as the most ignorant of their fellows. So it is with regard to the inhabitants of the sun. Do you think it is inhabited? I rather think it is. Do you think there is any life there? No question of it; it was not made in vain. It was made to give light to those who dwell upon it, and to other planets; and so will this earth when it is celestialized. Journal of Discourses, Volume 13, Page 271, 1870
So where did early Mormon leaders devise such tall tales about moon people and sun dwellers?
Well, all of the above quotes from Mormonism arose after 1835, the year when a tale of lunar habitation by humans was being spun by a paper called the New York Sun. A tale that later became known as The Great Moon Hoax.
In August of 1835 (just two years before Oliver B. Huntington said Joseph Smith began talking about inhabitants of the moon) the New York Sun (a paper from Joseph Smith’s own home state) reported that British astronomer Sir John Herschel discovered people living on the moon (as well as unicorns and hut-dwelling, fire-wielding bi-ped beavers).
Of course, thanks to advancements in astronomy, we now know for certain that men do not live on the moon (or the sun) and modern Mormons have since back-peddled from these teachings (painting over them with a veneer that these were only their leaders’ “opinion”). But even though they recognized the foolishness of these teachings, they still believe in extra-terrestrial habitation on other planets . . . just not on our moon or sun.
Mormon prophet Brigham Young said:
Mankind are here because they are the offspring of parents who were first brought here from another planet, and power was given them to propagate their species. Journal of Discourses, Volume 7, Page 285, 1859
Joseph Fielding Smith, tenth prophet/president of the Mormon organization, said:
We are not the only people that the Lord has created. We have brothers and sisters on other earths. They look like us because they, too, are the children of God and were created in his image, for they are also his offspring. Doctrines of Salvation, Volume 1, Page 62
Recognizing the prophets’ errors of claiming the moon and sun are inhabited is honest and the right thing to do, but why still cling to the idea that other planets are inhabited?
I’m still waiting for LDS apologists to finally concede that the Book of Mormon was just Joseph Smith’s “opinion” as well since advancements in archeology have not revealed one city, town, sword, shield, coin or other artifact or location in Book of Mormon history; advancements in DNA science have proven that American Indians are not descendants of ancient Hebrews as the Book of Mormon claims; that there is not one ancient manuscript to support the authenticity of the Book of Mormon; that the “Reformed Egyptian” language Joseph Smith supposedly translated the Book of Mormon from has never existed; and that the Book of Mormon (called “the most correct of any book on earth”), has undergone 3,913 documented changes, corrections, and alterations since it’s original 1830 publication.
But I suppose, even in the face of all that evidence, the odds of Mormons admitting that the Book of Mormon was a fabrication is as slim as finding Quakers living on the moon.