Orson Pratt teaches that Adam was the first person placed on this earth and, after committing transgression, was cast out of the Garden.
Orson Pratt, "Meeting of Adam With His Posterity in the Valley of Adam-Ondi-Ahhan—Location of the Valley—the Covenant With Enoch—Records of God's Dealings With Men From the Period of the Creation—Method of Preserving the Records of Ancient Prophets—Christ's Advent Among the Nephites—Fufillment of God's Purposes and the Fullness of Times," Journal of Discourses, 26 vols. (Liverpool: Joseph F. Smith, 1874), 16:48
Adam was the first personage placed on the earth, in the Garden of Eden, and having transgressed, and having been east out of the Garden of Eden, and having fulfilled a long probation, amounting to almost a thousand years, he concluded to gather together his children, which he did three years previously to his death. As recorded on the same page, he gathered Seth, Enos, Cainaan, Mahalaleel, Jared, Enoch and Methuselah, who were successive descendants, making eight generations in all, including himself, into the valley of Adam-ondi-ahman. This was nearly a thousand years after Adam was placed in the Garden of Eden, seven generations of his children, or the righteous portion thereof, were gathered together in that valley. And here it may not he amiss for me to say a few words in relation to the location of that interesting meeting or conference.