[John A. Widtsoe]
... the Lord made the earth and in the making He may have done many things not according to my particular opinion, but whatever He did He had a right to do. If He chose to place man-like beings upon the earth before the days of Adam, I really have no right to find fault with that any more than with the placing on the earth of the great variety of life which we know lived there. There is nothing definite in the scriptures or in modern revelation as to the age of the earth. Personally, I take discoveries relative to hat subject at face value, and set aside for later consideration the theories of men. Often there are contradictory theories in men's interpretations of facts. I have often said, as you say in your letter, that Adam was no doubt upon this earth long before it had reached the condition to permit a Garden of Eden to be planted, for he was one of those, who under God's command, organized the earth. Neither am I upset over the statement that Adam's was the first flesh upon the earth, because it seems from the context and from common sense, for that matter, that that means the first flesh of Adam's kind. There is so much connected with these matter that we do not understand that I am willing to take what little we know of a factual nature without offering any interpretations that may mislead others.
[Source: John A. Widtsoe, Letter to Albert R. Lyman, as quoted in Minutes of the Apostles of The Church of Jesus Christ of Latter-day Saints, 1835-1951, Electronic Edition, 2015]