Why would Joseph Smith think that Mesoamerican Indians had writing at all, when none of the Indian tribes known to Joseph Smith had it?

One obviously important aspect of the Book of Mormon is that the people had writing. This is curious because the Indian tribes Joseph Smith would be familiar with had no writing.

Bruce E. Dale and Brian Dale explain:

The Mesoamerican Indians (not just the Maya) had a rare or absent trait: they had writing. And so did the Book of Mormon peoples. Furthermore, the genealogy of their writing is complex. It is not clear how Mesoamerican writing arose, and the sacred written language of the Book of Mormon authors was known to them alone (Mormon 9:34). The correspondence is also unusual. None of the Indian tribes known to Joseph Smith had writing. Thus it was an extremely lucky (or foolhardy) “guess” on his part to have claimed in his “fictional” book that some American Indians did have writing. But he did claim it, and he was right. This correspondence also deserves a much smaller likelihood than a 1 in 50 chance, more like 1 in a million.
– Bruce E. Dale and Brian Dale – Joseph Smith: The World’s Greatest Guesser (A Bayesian Statistical Analysis of Positive and Negative Correspondences between the Book of Mormon and The Maya)

Why would Joseph think the ancestors of the Indians were more advanced than their descendants?

See:

Bruce E. Dale and Brian Dale – Joseph Smith: The World’s Greatest Guesser (A Bayesian Statistical Analysis of Positive and Negative Correspondences between the Book of Mormon and The Maya)

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