At one time animals were harmless  -  all animals-  because they did not crave flesh. The idea of mudering flesh came from man  - man introduced death to all creation - as it's head. They follow the head, wherever he leads. All sin comes from some form of fleshly craving or desire and death comes from sin.

When Cain slew Abel, it was the first deaths to ever occur on planet earth that was not done by God. God slew animals to provide clothes for Adam and Eve, but of course when He did so  - it was not a sin. When Cain slew Abel, he sinned by cutting short the life God had decreed Abel should live. Yet still - animals did not follow suit till adter the flood, which helped them to survive each other on the Ark, especially when getting on and off the Ark.

Each body, animal or human, was created by the Eternal God to live forever in companionship with Him. This is why it took so long for their bodies to die. The generations immediately following Adam took much longer to die than we do. There is no such thing as dying of "natural causes"  - death is unnatural,  it was never meant to be a part of our existence. 

Our Father, which art in Heaven, hallowed be His name, is the source of holiness and life. Sin seperated us from Him: that's when death entered in to the world. Man chose to please himself instead of God. He chose to listen to and obey Satan's voice rather than their Father's.  So, eating from the tree of the knowledge of good and evil brings death, to our souls and then to our bodies for EVERYTHING SEPERATED FROM OUR FATHER DIES....man is seeking to know good and evil apart from the creator and planter of the tree of the knowledge of good and evil.  Mankind wants to decide his own fate. We want to exist apart from Him  - denying Him the very purpose for which we were created: to be His people,  in loving relationship with Him.

Christ is the Tree of Life, offered to us a second time  - another chance to get it right, to correct our mistake ( we all partook of the tree of the knowledge of good and evil in Adam ) and we all may eat of the Tree of Life because of the Second Adam  - the Word of God made flesh is the Tree of Life we are to eat, daily, to survive in a world eating from the tree of death. The "Life" the tree bears for us is Eternal, which is why we were banned from eating it (fellowshipping with,  walking and talking with, our Father, in the midst of the garden in the cool of the evening) after we sinned by eating of the tree of rebellion because if we had eaten of the Tree of Life then, after we ate of the other, we would be in an eternal state of sin and separation from God, otherwise known as damnation. Death is God's mercy to us, that there can be and is an end to our sinful state of being and there is a restoration to who we were before the Fall. We will be and are restored to our glorified,  eternal bodies that He prepared for us before Adam sinned,  for indeed, even every creature will be restored to their original condition,  their eternal state of being, at the glorious ressurection of the dead....a factory reset if there ever was one! "The wolf and the lamb shall feed together,  and the lion shall eat straw like the bullock", "They shall not hurt nor destroy" anymore for sin shall be no more, therefore death shall be no more  "O death, where is thy sting?" We Christians thank God for death's demise, the "death of death" but sinners lament because at the Judgment,  all will abide in death or life forever.  All will eat the fruit of of one tree or the other  - forever, for the greatest torment in Hell will come from "The knowledge of good and evil"  - from knowing how evil they really were and are and from knowing how truly good God was to them in their lives (and is) and how good the Saints were (and are). The knowledge they chose will accompany them in Hell and the lake of fire, tormenting them forever.  They chose knowledge of themselves over knowing Him. All mankind is hungrily pursuing knowledge today. They crave it more and more and more, as Daniel put it  - "many shall run to and fro, and knowledge shall be increased"; an increase of knowledge, then, is a sure sign of the time of the end and it has happened in our generation before our very eyes with the advent of the Internet. There is more raw knowledge available on the earth today than at any other time in man's history.  Even Bible schools, even churches are fixated on seeking knowledge  - some may be seeking the knowledge of the Most High but the point is this  - we should center our lives on Him, on knowing Him, not merely knowledge about Him even it's from Him. 

Part two in Four days