[10]  Why do we die?

Adam's sons and daughters are born condemned to death under the death penalty passed and executed on Adam by God upon the very day that he sinned (3993Nisan14). But he was passed over and received a gene zap resurrection whereby his ageless non adamic edenic body was transformed into a 960 year max lifespan aging adamic body, thanks to the mercy of God and the ransom sacrifices of Jesus Christ - see I47. 

If you do not believe that Adam and Eve were real, the death penalty that all mankind still suffers is certainly real enough and does not require any level of belief. Consider the maternal (expressed in terms of the husbands of the maternal tree) genealogy of Jesus in Luke3 - see intro6. Then ask yourself: Which one of these patriarchs do you believe did not exist? For the entire chronology of man from Adam to Armageddon please see U101.

Even today scientists do not understand why a human body, which has the capability to fix itself, grows old and kills itself. Where is the evolutionary advantage in that? Like any other human, Adam could only pass on to his sons the life that he had. He could not pass on everlasting life to them, because he himself only had a finite life once his DNA had become aging before he began to have children after he was thrown out of the garden. 

When Adam sinned (on 3993Nisan14 BC, when he was 33½ years old) by eating the fruit of the tree and breaking the one and only law upon him, he would have died permanently had the angel Michael not agreed to ransom him angelically and had God not given Michael and human body to ransom him humanly as well. The love of these two extended his life in this system until 3097 BC, some 896 years later (since he lived to be 930 years old). During this time Adam and Eve had many children, both sons and daughters, and these interbred to form the very long lived pre-flood patriarchs of Genesis 5. Here is a list of their lengths of life as specified in Genesis 5...

The pre-adamic humans from whom Adam was begotten (just as Jesus, the last Adam, was born of Mary and Joseph but was God's son), lived as humans for a maximum of 50 years - see intro5. The sons and daughters of Adam would have been forbidden from marrying pre-adamic partners before the flood, just as the Jews were forbidden to marry the Gentiles under the Law of Moses. Certainly those in the table above did not interbreed with the pre-adamics, since they all lived to a very ripe old age! The way that God executed the physical death penalty on Adam and on Eve and hence on all mankind is that he changed their genes from indefinitely lasting to finitely lasting. Adam and Eve did not age physically in the Garden of Eden, which paradise was a prophecy for the kingdom of God which is soon to come. The bible describes our parents loss of non ageing bodies as follows...

22 And Jehovah God went on to say: Here the man has become like one of us in knowing good and bad, and now in order that he may not put his hand out and actually take [fruit] also from the tree of life and eat and live to time indefinite [I will have to act].
23 With that Jehovah God put him out of the garden of Eden to cultivate the ground from which he had been taken (Genesis 3).

So if the pair had remained in the garden, eating from the tree of life, then they would not have died. So their bodies cannot have been ageing in the garden. So God changed their genes to the slowly dying variety that we all know today at the time of their sin. 

We are told that God made them some long garments of skin to wear as they left the garden. He did this physically because they only realised that they were naked after they had discovered sexual desire. And Adam only discovered sexual desire when Eve used it on him to get him to eat the fruit. It is not easy to see this from Genesis 3 (although it is possible), we know this happened because the whole story is an archetype for the way Satan uses women to get to men today. He tempts women into sin using their desire for status, and they tempt men into sin using man's desire for sex. And Eve only discovered sexual desire when Satan introduced her to it when he appeared to her as a human acting like a snake in the tree. He abused her desire for status to get what he wanted. He wanted to get Adam to sin, in order that he could be the progenitor of man not Adam. So he sold knowledge of bad to Eve by telling her that if she ate from the tree she would be like God (having a vastly increased status) knowing good and bad.

4 At this the serpent said to the woman: Ye positively will not die [literally to die ye will not die].
5 For God knows that in the very day of your eating from it your eyes are bound to be opened and you are bound to be like God, knowing good and bad (Genesis 3).

Whereas God had said...

16 And Jehovah God also laid this command upon the man: From every tree of the garden you may eat to satisfaction
17 But as for the tree of the knowledge of good and bad you must not eat from it, for in the day you eat from it dying you will die [or to die thou will die] (Genesis 2).

The man knew the precise wording of the commandment from Jehovah. But Elohim (the first Holy Spirit - run by Satan) dishonestly added to that command when relaying it to Eve. So that Eve had the commandment not from Jehovah Elohim, but from Elohim as follows...

2 At this the woman said to the serpent: Of the fruit of the trees of the garden we may eat. 
3 But as for [eating] of the fruit of the tree that is in the middle of the garden, God [Elohim - not Jehovah Elohim] has said, 'You must not eat from it, no, you must not touch it that you do not die.' 

Satan would have been able to say to Eve, look touch the fruit I promise you, you will not die. Either Satan deliberately overstated God when he was relaying the commandment to Eve on God's behalf (Elohim has said) or Adam added to God's commandment when relaying it to Eve in the first example of bureaucratic creep. But mankind, following his example, has been adding to the commands of God ever since...

9 It is in vain that they keep worshiping me, because they teach commands of men as doctrines (Matthew 15).

Eventually Eve was seduced by her desire for status and she ate. In fact, immediately before that, Satan had seduced Eve, for the purpose of producing Cain non adamically - see U314. This taught her to seduce Adam with his desire for her. 

Eve did not realise what she had done was bad until Adam explained it to her, she was thoroughly deceived. 

14 Also, Adam was not deceived, but the woman was thoroughly deceived and came to be in transgression (1 Timothy 2).

Presumably Eve had just reached puberty when she was introduced to Adam and so had no concept of sexual desire. Adam had been in the garden since he was 11 - see I6. So he had no concept of sexual desire either. We can deduce that both Adam and Eve grew up around twice as slowly as we do today, since they had a much longer life span and none of the pre flood patriarchs of Genesis 5 or the post flood patriarchs of Genesis 11 had any children under the age of 29, whereas today boys reach puberty at around 12-14 years old. So in modern terms Adam had the body of a 16¾ year old when he sinned aged 33½ years old and became sexually aware - see I6. Eve was presumably slightly younger. Once they realised that they were naked we read...

21 And Jehovah God proceeded to make long garments of skin for Adam and for his wife and to clothe them (Genesis 3).

The literal meaning of this is that God made them some clothes to wear from animal skins. But the concept of clothing our original parents is repeated. The true bible code, which is a symbolic code, tells us that successively repeated concepts have greater meanings. The greater meaning is that God gave the pair of them new 960 year max lifespan ageing bodies (very very long garments of skin).

These then are the garments of skin that we wear today (in a shorter variety). The death penalty that God passed on our parents exists and is enforced entirely by our genes, our bodies. We die due to ageing bodies, quite obviously, and we inherit these from Adam and Eve. So the sinner and the saint, the murderer and the doctor, die, not from whatever sins they may have committed during their lives, but actually from the death penalty executed upon our parents genes, which genes we all inherit.

Adam was designed to fail the test in Eden - the test was really upon Satan not Adam

The tree of knowledge of Good and Bad although billed as a test upon Adam was in truth a test on Satan not Adam. One cannot learn about good and bad so as to pass a test of righteousness before eating from the tree of good and bad - which is gaining knowledge and experience of Good and Bad so that one cane pass said test. It is only when a child starts rebelling against the law of his parents that the parents will begin the process of educating him and disciplining him in order to teach him right from wrong or good from bad. When Adam ate from the tree, this meant he was ready for that lesson. This world is that tree. For Adam was thrown out of the garden to prevent access NOT to the tree of knowledge of good and bad, but to the tree of life.  For life can only be granted to people who are reasonable students of God's righteousness (good and bad). That is people who have eaten a lot of fruit from the tree of good and bad.

20 For the creation was subjected to futility, not by its own will but through him that subjected it, on the basis of hope
21 that the creation itself also will be set free from enslavement to corruption and have the glorious freedom of the children of God. (Romans 8 NWT)

19 For the good that I wish, I do not do, but the bad that I do not wish is what I practice (Romans 7 NWT)

22 I really delight in the law of God according to the man I am within,
23 but I behold in my members another law warring against the law of my mind and leading me captive to sin's law that is in my members. (Romans 7 NWT)

We were created by God with flesh that desires to sin and we must overcome that desire with our minds, our spirits. Likewise God himself subjected mankind to futility by setting young Adam a task that he knew he would fail. God was never testing Adam. Adam was always going to fail because he had to learn about good and bad in order to get an education in sin and righteousness. This was always going to be the next step for Adam just as it is for any young child.