Joseph F. Smith notes that it has not been revealed if Adam and Eve were transplanted to this earth from another world with immortal bodies.
Joseph F. Smith (editor), "Priesthood Quorums' Table," Improvement Era 13, no. 6 (April 1910): 570
. . . whether the first parents of our generations, Adam and Eve, were transplanted from another sphere, with immortal tabernacles, which became corrupted through sin and the partaking of natural foods, in the process of time; whether they were born here in mortality, as other mortals have been, are questions not fully answered in the revealed word of God.