The Bible explains that Adam and Eve were created human and because they had eaten from the Tree of Knowledge Good and Evil, they became almost like God and the Angels.- Gen 3:22-24. They knew the difference between good and bad, which the rest of the animals did not. God kicked them out of the Garden of Eden to keep them from eating from the Tree of Life and becoming immortal- just like God. If they had been able to get to the Tree of Life, they could have lived forever. The implications are that Man was going to die anyway as a natural result of the life that God created. Humans do not die because of Sin and the loss of perfection. The first mention of sin in the Bible is in the Story of Cain and Abel, not Adam and Eve.
This means that mankind does not need a saviour to restore eternal life that Adam never had to start with, in the Garden of Eden. Adam and Eve are not responsible for our death or the notion that their sin has resulted in our death. 1 Cor 15:21-22
Man was always going to die, unless they ate of the Tree of Life and that never happened.