The temporary existence that ends in death is not God's original purpose for mankind.
God gave us physical, temporary life. Since we are physical, we all eventually face death. This is no accident of evolution but came about as a result of circumstances knowable only from the Bible—involving decisions made by our first parents in the Garden of Eden.
In the beginning of God's plan for mankind, God made available to Adam and Eve His gift of eternal life represented by the tree of life (Genesis:2:9, 16). This tree represented choosing to believe in and obey God's revealed will, embracing His way of life.
The garden contained another tree as well, the tree of the knowledge of good and evil (verse 9). This tree represented something altogether different—man choosing his own way of life rather than following God's revelation —deciding for himself what is good and evil.
Influenced by Satan, Adam and Eve made a fundamental choice that has affected humanity ever since. They chose to take of the wrong tree, eating the forbidden fruit. Refusing to believe and obey God, they came under the dominion of Satan and the penalty for sin—suffering and death (Genesis:2:17).
Had Adam and Eve taken of the tree of life, they would have received eternal life (Genesis:3:22). This is why, after they had made the wrong choice and had taken of the wrong tree, God had to cut them off from the tree of life "lest they live forever." God could not allow them to live forever in their sinful, rebellious state.
Because of their disobedience, God told them of their sure fate: "You [shall] return to the ground, for out of it you were taken; for dust you are, and to dust you shall return" (Genesis:3:19).
It is important to realize that God's original plan to give mankind eternal life, which was rejected by Adam and Eve, is available to each of us today as a result of God's personal calling.
Adam and Eve introduced sin to mankind, and all human beings springing from them are "appointed" to die because all have sinned (Romans:5:12; Hebrews:9:27). Yet God's purpose for mankind stands; His purpose to give mankind eternal life will succeed! Throughout the rest of the Bible we see the unfolding of God's plan of redemption—the purchase of mankind for a price. Man, we see, is able to be rescued from death because of the priceless shed blood of the Son of God, Jesus Christ.
The little-understood truth is that God's initial purpose for mankind is that he not die. The temporary existence that ends in death, bringing suffering and loss, is not God's original purpose for mankind. It is part of the curse for sin brought on humanity by the wrong choice made by our first parents, and all have chosen to follow that sinful way ever since (Romans:3:23).