A fallen world
Modern science teaches that physical death began on earth when life began, millions of years ago. In contrast, "latter-day revelation teaches that there was no death on this earth for any forms of life before the fall of Adam." (Bible Dictionary, "Death.") When Adam fell, "the earth itself became subject to death [and] a change was wrought over the whole face of the creation, which up to that time had not been subject to death." (Teachings of Presidents of the Church: Harold B. Lee, 20.)
We live in a fallen world. The very words "fallen world" suggest an earlier, higher state of existence. James E. Talmage, Joseph Fielding Smith, David A. Bednar, and Jeffrey R Holland have each contributed to our understanding of the phrase "fallen world." James E. Talmage: "The Garden Room ... ceiling and walls are embellished with oil paintings—the former to represent clouds and sky, with sun and moon and star; the latter showing landscape scenes of rare beauty. There are sylvan grottoes and mossy dells, lakelets and brooks, waterfalls and rivulets, trees, vines and flowers, insects, birds and beasts, in short, the earth beautiful,—as it was before the Fall. It may be called the Garden of Eden Room, for in every part and appurtenance it speaks of sweet content and blessed repose. There is no suggestion of disturbance, enmity or hostility; the beasts are at peace and the birds live in amity....
"The World Room.... From Eden man has been driven out to meet contention, to struggle with difficulties, to live by strife and sweat. This chamber may well be known as the room of the fallen world, or more briefly, the World Room." (The House of the Lord, 157-158.)
Joseph Fielding Smith: "It is a fallen world. It has been a fallen world since Adam was driven from the Garden of Eden." (Doctrines of Salvation, 1:308.)
Joseph Fielding Smith: “Modern education declares that there never was such a thing as the fall of man, but that conditions have always gone on in the same way as now in this mortal world. Here, say they, death and mutation have always held sway as natural conditions on this earth and everywhere throughout the universe the same laws obtain. It is declared that man has made his ascent to the exalted place he now occupies through countless ages of development which has gradually distinguished him from lower forms of life.
“Such a doctrine of necessity discards the story of Adam and the Garden of Eden, which it looks upon as a myth coming down to us from an early age of foolish ignorance and superstition. Moreover, it is taught that since death was always here, and a natural condition prevailing throughout all space, there could not possibly come a redemption from Adam’s transgression, hence there was no need for a Savior for a fallen world.” (Old Testament: Student Manual, Genesis—2 Samuel, Third edition, 2003, 42.)
David A. Bednar: "We live in a fallen world. The very elements out of which our bodies were created are by nature fallen and ever subject to the pull of sin, corruption, and death. Thus, the Fall of Adam and its consequences affect us most directly through our physical bodies." (Ensign, Sep. 2001.)
David A. Bednar: "It is not just that the Son of God brought light into a darkened and fallen world; He is the Light (see 3 Ne. 11:11)." (New Era, Oct. 2005.)
Jeffrey R. Holland: “A life without problems or limitations or challenges—life without ‘opposition in all things,’ as Lehi phrased it—would paradoxically but in very fact be less rewarding and less ennobling than one which confronts—even frequently confronts—difficulty and disappointment and sorrow. As beloved Eve said, were it not for the difficulties faced in a fallen world, neither she nor Adam nor any of the rest of us ever would have known “the joy of our redemption, and the eternal life which God giveth unto all the obedient.’” (Ensign, Nov. 1996.)