The key verse for understanding the punishments associated with eating from Tree of the Knowledge and Good and Evil is Genesis 2:17. In English:
but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall surely die.”
Much ink has been spilt over the question of why that death was not immediate. For purposes of this argument, I will fall on an assumption that God's mercy was on display here, and he withheld that execution for hundreds (at least in Adam's case, 930) of years. That God continually doesn't kill people who deserve it in Genesis (Cain - not killed; Lamech - not killed; World before the Flood- not killed for 120 years; World at Babel - not killed) shows that God's mercy is evident even in the first 11 chapters of Geensis.
What is important in this context, however, is the nature of death and life, as used in Genesis 2:17 and 3:22.
In Hebrew, the key phrase of death centers around the "m-t" מוֹת
מוֹת תָּמוּת = "in that day you shall surely die"
In every other instance throughout the Hebrew text, the "m-t" words speak of a physical death - the separation of the ru'ach - the breath - from the body. Other usages imply both natural deaths and execution. When people were put to death, indeed, their lives were m-t. (Sorry, couldn't resist!)
This could then seem to indicate at a very simple level that there was no death. In Revelation 21:4, it says:
He will wipe away every tear from their eyes, and death shall be no more, neither shall there be mourning, nor crying, nor pain anymore, for the former things have passed away.”
If "the Fall" is indeed a dispensationary event in which "all former things pass away," then it is not unreasonable to say that prior to the Fall, there was no death. Evidence for this view could be drawn from Genesis 9, another dispensationary event in which "the old order passes away." After the Flood, Noah is told:
2 The fear of you and the dread of you shall be upon every beast of the earth and upon every bird of the heavens, upon everything that creeps on the ground and all the fish of the sea. Into your hand they are delivered. 3 Every moving thing that lives shall be food for you. And as I gave you the green plants, I give you everything.
Here, the evidence clearly seems to indicate that man was at least not allowed to kill animals, and that animals were not afraid of man. It is not too much of a stretch to suggest then that had "the Fall" not occurred, there would have been no physical death.
Indeed, when in Genesis 3:22, the Lord says:
He must not be allowed to reach out his hand and take also from the tree of life and eat, and live forever.
there is nothing to preclude that from meaning a physical immortal life.
Indeed, the wa-hey (to live) and olayim (forever), would connote "go one breathing indefinitely."
inf. absol, חָיֹה Eze. 18:9, and חָיוֹ 3:21; 18:28; constr. with suff. חֲיוֹתָם Josh. 5:8; with prefix לִחְיוֹת Eze. 33:12; imp. with prefix וֶחְיֵה Gen. 20:7; pl. וִחְיוּ 42:18; fut. יִחְיֶה apoc. יְהִי, וַיְחִי.
(1) TO LIVE, a word of very frequent use. Arabic حَىَّ, which form is also found in Hebrew, see חָיַי. Æth. ሐይወ፡ Syr. ܚܝܐܳ id. The original idea of this word is that of breathing; inasmuch as the life of animate beings is discerned by their breathing (compare נֶפֶשׁ); and the more ancient form of this root is הָוָה, which see. The same original idea is found in the Greek ζάω, ζώω, cognate to which is ἄω, ἄημι, to breathe; which, in Æschylus, is applied to the winds as breathing or blowing. Those who are curious in languages may inquire whether the Sanscrit dschîv, to live; Greek βίοω; and Latin vivo; belong to the same stock.
Gesenius, W., & Tregelles, S. P. (2003). Gesenius' Hebrew and Chaldee lexicon to the Old Testament Scriptures (273–274). Bellingham, WA: Logos Research Systems, Inc.
A very simple explanation could then be derived as follows:
When Adam and Eve were created, there was no concept of death. Being made "very good," could imply that there would be no inherent reason for the body to die of old age, rather it would keep going on forever.
The choice of two trees - a Tree of Life and a Tree of the Knowledge of Good and Evil - would have been placed in the Garden, and the named gifts associated thereto be actual powers adhering to the creatures. Indeed, the text clearly states that when the woman and the man had eaten of the tree, "their eyes were opened." This seems to indicate that a physical effect of some kind had taken place.
When the Tree of the Knowledge of Good and Evil was eaten, the race had been decided - man had chosen "to be like God" over physical immortality. At that point, the nature of man was cemented.
The Tree of Life, which would have cemented the ongoing "Zoe" (life) would itself not have been affected - it still would have "sealed the deal" in the other direction, cementing ongoing breath and spirit within the body. Had it too been eaten, both powers would have adhered to the creatures, making them both "wise" and "immortal."
Had God then seen this as a race to which Tree would be eaten of first, having both powers was not part of the deal. He thus was compelled to keep the man (but interestingly not the other created beings such as the animals or even the angels) from the Tree, at least until the Flood, lest that power be transmitted as well.
Finally, when it comes to this notion of life, Psalm 90 should be considered:
Before the mountains were born
or you brought forth the whole world,
from everlasting to everlasting you are God.
3 You turn people back to dust,
saying, “Return to dust, you mortals.”
4 A thousand years in your sight
are like a day that has just gone by,
or like a watch in the night.
5 Yet you sweep people away in the sleep of death—
they are like the new grass of the morning:
6 In the morning it springs up new,
but by evening it is dry and withered.
7 We are consumed by your anger
and terrified by your indignation.
8 You have set our iniquities before you,
our secret sins in the light of your presence.
9 All our days pass away under your wrath;
we finish our years with a moan.
10 Our days may come to seventy years,
or eighty, if our strength endures;
yet the best of them are but trouble and sorrow,
for they quickly pass, and we fly away.
11 If only we knew the power of your anger!
Your wrath is as great as the fear that is your due.
12 Teach us to number our days,
that we may gain a heart of wisdom.
(I will admit, I love the "threescore and ten" but 70 - 80 years is a better translation). While death is obviously the key facet of the human condition, it should be noted that in God's eyes, it too serves a purpose. It both reflects God's wrath and punishment (as described in verses 7 - 9) and leads us to wisdom, as it forces us to use what we have wisely.
Had Adam and Eve not eaten of either tree, I do not know if their bodies would have worn out. Had they eaten of the Tree of Life, the implication seems to be that it would not have. But, as it is, we ate of knowledge, and we know good and evil. The serpent did not lie - our eyes were opened, and we became like God, in that we understood what was good and what was not. With that knowledge, we understand that death is bad. We are thus constantly reminded that with the power of this knowledge, we must choose to make the most of our earthly time and honor God therein.
In the Resurrection, if Paul is to be believed, we will see the fruits thereof. 1 Corinthians 15 states:
23 But each in turn: Christ, the firstfruits; then, when he comes, those who belong to him. 24 Then the end will come, when he hands over the kingdom to God the Father after he has destroyed all dominion, authority and power. 25 For he must reign until he has put all his enemies under his feet. 26 The last enemy to be destroyed is death.
If with the Tree of the Knowledge of Good and Evil, God created death, then in the final Resurrection, death is destroyed. At that point, we would be in the same place we were in the Graden - nothing inherently capable of stopping our breath from our physical forms. We know we will be raised and given new incorruptable bodies - and clearly something would be needed to restore our essence to them.
Is that essence (let's call it a soul) then immortal? Until eternity begins, its really a moot question. Are those who are not resurrected annihilated? Again - separate question. The point is back to the proof text given by your JW friend. The soul is not the point of Genesis 3:22 - it is the breath, the spirit. In short, your friend's argument, while interesting, is a non-sequitir.
We will die or else we will be caught up in the air with him.
We will be resurrected and we will know, even as we are known.
In any event, God did not mis-speak. The bodies he created for the present must not live forever. Whether or not their souls do rests on a completely different foundation.