Satan and sin, along with death and war, seem inseparably linked. Who casued this in the first place?

This question actually has a two part answer. The obvious choice of who brought sin, death and war, etc. into existence was Satan the �god of this world.� (2 Cor. 4:4) Satan and sin then remained inseparable. In the remote past Satan desired to have his own sphere of authority, just as God ruled the universe. (I will be like the most high) Even though he was an angel of the highest order, endowed with gifts and abilities far above all the angelic creation, (Ezek. 28:13-15) he longed to �be like God.� (Isa. 14:13, 14) He did not covet God�s position as master of the universe, but wanted someone who would worship only him and follow his every dictate. When man was created, Lucifer (later named Satan or adversary of God) saw his opportunity.

The fall of man into sin, evil and death, started with Satan persuading Adam and Eve to disobey God. For centuries he has posed as a messenger of light (2 Cor. 11:14). With our first parents he convinced them that God was not interested in their welfare and that he was imprisoning them, keeping them from knowledge and enlightenment that would make them wise�something perfect human nature will eventually desire.  Satan convinced them that God had lied about death resulting from the eating of the �tree of the knowledge of good and evil.� As proof of this he convinced Eve that if she partook of the fruit of this tree she would not die. To fortify his argument Satan, working through a serpent, ate of the forbidden tree, proving to Eve that death did not instantly come from merely the eating of fruit. Subsequently Eve convinced Adam to do the same, and he following her into death because of his great love for her�he could not envision himself alone again. And immediately mankind was plunged into death, with all its concomitants of sin, evil and suffering.

But on the other hand, Adam bore some responsibility for his own downfall. The scriptures tell us that Adam was not deceived. (1 Tim. 2:14) Had Adam and Eve loved God supremely and trusted him regardless of the circumstances, matters would have turned out differently for Adam and Eve and their posterity. As Jesus expressed it, love for the Creator is the essence of the Law (Mark 28-31) Even today, if this were possible, sin would fade away, and there would be no more hatred, malice, greed, anger, wars, etc. because if mankind loved his Creator; love for his neighbor would be the result. Truly, man has been the master of his own destiny.
  
As the centuries rolled by mankind found himself on a slippery slope, ever heading downward, and powerless to stop his fall towards death. Because man now had to work by the sweat of his brow merely to exist, life became a constant struggle to keep body and soul together. As man got further from perfection, the physical qualities ruled, while the mental qualities diminished. In many ways, man was living and acting on the animal level. This produced every kind of evil: greed, hatred, anger, malice (Col. 3:8-10; Eph. 4:31-32; Titus 3:3�traits of fallen man) Think of how soon the first murder took place. Mankind�s downward course is succinctly portrayed in Romans 1.

Since the fall, sin is ingrained in mankind�s being and the weaknesses of mankind have been passed from generation to generation�genetics playing a part in man�s fall from perfection. (Jer. 31:29) And, since the fall Satan has manipulated man and his circumstances and his weaknesses to bring about greed and every evil imaginable.

But this experience with Satan and sin and death is not forever. When all mankind is again brought forth from the grave (John 5:28, 29), they will be given every opportunity to learn righteousness and God�s will. Satan will be bound and unable to adversely influence mankind. This long experience with sin and death will give him a benefit that Adam and Eve never had�the contrast of good and evil and the benefits of doing what is right as opposed to what is wrong. If man chooses the right he will live on this earth forever in perfect and in harmony with God and all mankind.