JRR Tolkien argued in one of his philosophical fictional works from the Middle-Earth Lengendarium,
Athrabeth Finrod ah Andreth, that the natural mode of human passing into the world beyond prior to the Fall would have been by means of “assumption” rather than physical death - as in the Virgin Mary, the reputed “assumption” of Enoch and Elijah. I thought it was an interesting idea but there is of course issues ie mankind could not have had glorified bodies without the coming of Christ and his resurrection (the firstfruits of the new humanity with glorified bodies like unto his own), or could they - given also that God exists beyond time? Would God have glorified their earthly bodies so that they might pass from the temporal world into timeless identity with spiritual bodies of real transformed matter but not subject to death, decay, space, time or any physical constraints and dominated by the spiritual soul rather than the will of the flesh?
Christopher Tollkien stated in his commentary:
The Athrabeth Finrod ah Andreth perhaps marks the culmination of my father’s thought on the relation of Elves and Men, in Finrod’s exalted vision of the original design of Eru for Mankind; but his central purpose was to explore full for the first time the nature of ‘the Marring of Men’.
In the tale Andreth, a mortal woman, describes to the High Elf Lord Finrod that Men believe that they themselves were once immortal even as the Elves were. Finrod, however, recognizes that
their ‘immortality’ cannot have been the longevity within Arda of the Elves; otherwise they would have been simply Elves, and their separate introduction later into the Drama by Eru would have no function
At the core of the distinction between Men and Elves is the idea that the separation of fëa and hröa (roughly equivalent to body and soul) is not a natural condition and results not from the original design, but from the “Marring of Arda” by Melkor. The fëar of the Elves was bound to the Time of earth.
The fëar of Men, on the other hand, left time altogether at the time of death. Finrod places a very different interpretation on the “disaster” that befell Men in their Marring then Andreth does. As Tolkien puts it in the Commentary:
He therefore guesses that it is the fear of death that is the result of the disaster. It is feared because it now is combined with severance of hroa and fea. But the fear of Men must have been designed to leave Arda willingly or indeed by desire - maybe after a longer time than the present average human life, but still in a time very short compared with Elvish lives. Then basing his argument on the axiom that severance of hroa and fea is unnatural and contrary to design, he comes (or if you like jumps) to the conclusion that the fea of unfallen Man would have taken with it its hroa into the new mode of existence (free from Time). In other words, that ‘assumption’ was the natural end of each human life, though as far as we know it has been the end of the only ‘unfallen’ member of Mankind.
In this manner Tolkien envisaged pre-Fall man (minus the first sin) being assumed into heaven, eternity or timelessness, at an opportune moment chosen by the will of their rational souls after an extended period of time, perhaps in response to an inspiration or call from God telling them that their purpose had been fufilled and that they could ‘move on’, rather than forcibly expiring by means of physical death and the unnatural (to man) separation of body and soul.
This makes sense on one level since man has a spiritual soul which has its eyes set not on this world but on a world to come, the New Heavens and Earth toward which this current imperfect universe is striving and groaning and journeying.
Even had we not sinned and become subject to death, I do not think that humanity would ever have been “immortal” in the sense of always existing on earth for millenia bound within temporal time. Man loves the earth but looks beyond it, because it is ultimately through man - both matter and spirit joined in perfect harmony - that creation will reach its perfection, through the desire of his rational soul in his material body to transcend time and impermanence
with his material form still in tact, thus elevating creation above itself, towards the perfection for which it longs. We are matter that has become aware of itself and has a longing for eternity, for timelessness beyond time. It is that desire to rise up with our material body and transcend this temporal universe which is the perfection of the entire created order - now realized through Christ, who is fully human yet fully divine but still through “man” (God made man).
Am I making sense? I am suggesting that Tolkien, while not a theologian, might have had a genuinely accurate point in surmising that man’s ultimate destiny would not have been immortality for all time within earth/material universe until its ultimate destruction but rather an assumption beyond it with his material body in tact, thus elevating and perfecting creation, driving it towards its ultimate goal which is eternity.
Man thus occupied a kind of intermediate role between the spiritual and material worlds and acted, in God’s plan, as a “bridge” between the two, linking the two and perfecting the material universe - almost “redeeming” it - through his co-operation with God in tending the earth and then “transcending” it through assumption with his body and soul together.