Kerry Muhlestein, professor of ancient scripture at Brigham Young University, PhD in Egyptology at UCLA in 2003.
We can be fairly certain when the papyri fragments we still have were written. They were created in about 200 BC.i That is roughly 2000 years after Abraham lived. However, this has little bearing on whether or not Abraham authored the original text. He certainly did not author the manuscript that fell into Joseph Smith’s hands, but that has no bearing on whether he was the author of the text.
To illustrate, the earliest copy of the Book of Isaiah also dates to about 200 BC.ii Isaiah lived about 500 years before this. But no one has claimed that this means Isaiah did not write the Book of Isaiah (some do not believe there was an Isaiah, and some believe the Book of Isaiah was written by several people, but none of this is due to the 200 BC date of our earliest manuscript). Everyone is aware that whatever Isaiah wrote was copied again and again for hundreds of years, and that the manuscript we now have is a copy of a copy of a copy. This is true for most ancient texts we know about. We do not have the original Epic of Gilgamesh, Illiad, or Epistle to James. None of this has any bearing on whether or not the texts are of ancient date. The transmission process for all ancient texts is complicated, and is seldom fully understood for any given text. I wish I understood more about the transmission process behind the Book of Abraham just as I do for the Book of Samuel, The Egyptian tale of the Shipwrecked Sailor, and the Egyptian Instructions of Ptahotep.
A question we should ask ourselves is how the writings of Abraham may have ended up in Egypt nearly 2000 years after his death. Of course we do not know the answer, but there are many possibilities. Abraham himself spent time in Egypt and could have left some of his writing then. If this is the case then those writings were cared for by Egyptians for millennia. It seems more likely that his writings were cared for by his descendants and passed back into Egypt at a later date. They could have come with Jacob’s family as they took up their sojourn in Egypt. Even more likely is the idea that they could have come with the large infusion of Jews that entered Egypt after Babylon destroyed Jerusalem in 586 BC. From that time forth there was a steady flow of Jews coming in and out of Egypt.iii The Jewish population in Egypt experienced great growth right around the time the papyri Joseph Smith owned were created. It was also a time when Egyptians were collecting such documents from foreign populations. In short, there are countless possibilities over two thousand years, but most especially in the few hundred years before 200 BC, when the text of the Book of Abraham could have come into Egyptian hands.iv
We must also realize that Joseph Smith was not an expert on such transmission processes. He may have assumed that if a text was written by Abraham that the copy he owned was the original document created by Abraham. He had no educational background that would have led him to believe otherwise, and we should not assume that the Lord would feel a need to correct him in this matter (for more on this see http://www.youtube.com/watch?v=CzP0iuNLa10&list=PLc5yYrpPFm2sT29LjdbicouCVVWdaA0BW). Instead the text must be judged on its own merits, applying both our full mental and our full spiritual capacities in such an evaluation.v
i See Kerry Muhlestein, “Egyptian Papyri and the Book of Abraham: A Faithful, Egyptological Point of View”, 223.
ii See Kerry Muhlestein, “Egyptian Papyri and the Book of Abraham: A Faithful, Egyptological Point of View”, 230.
iii See Kerry Muhlestein, “The Religious and Cultural Background of Joseph Smith Papyrus One,” in The Journal of Book of Mormon and Other Restoration Scripture 22/1 (2013), 20-33.
iv See also Kerry Muhlestein and Courtney Innes, “Synagogues and Cemeteries: evidence for a Jewish presence in the Fayum,” in Journal of Ancient Egyptian Interconnections, 4/2, 2012, 53-59.
v On one such evaluation, see http://maxwellinstitute.byu.edu/publications/jbms/?vol=22&num=1&id=652.