What does Romans 5:12 mean?
Earlier, Paul explained that salvation on the basis of faith brings us peace with God. We can hope in Him, and trust Him, since He has so clearly shown His love for us (Romans 5:8). Paul begins a new section in this verse in which he will compare the work of Adam, as the representative of sinful humanity, with the work of Christ, on behalf of sinful humanity. This further explains the ideas of human sin, Christ's sacrifice, and our salvation, all of which have already been introduced in this letter.Paul starts with Adam, though he is not mentioned by name for several verses. Paul states that sin came into the world through one man. This one man is Adam, the first man created from dust by God Himself (Genesis 1:27). God breathed life into Adam and placed him in the garden of Eden with only one restriction: Don't eat from the tree of the knowledge of good and evil (Genesis 2:15–17). Adam, along with his wife, Eve did exactly what they were told not to, and sin entered the world.
It's worth noting here that the term "world," in this context, is specifically a reference to humanity. Paul's discussion here is entirely focused on the relationship between human beings and God. Interpreters differ on whether or not this verse supports that all death—including that of animals—is implied in this statement.
What's clear from Paul's argument here is that death followed sin, as God said it would. First, God slaughtered an animal to provide clothing for Adam and Eve, suddenly made aware of their nakedness by their sin (Genesis 3:21). More than that, though, Adam and Eve were sent away from God and from the garden and began to die physically. They became mortal beings with a limited lifespan. Even worse, Adam and Eve passed on their sin to their offspring. Every person ever born in the world, other than Christ (Hebrews 4:15) was born sinful and destined to die. Sin always leads to death, as Paul will make clear in the following verses.
This was the tragic and seemingly inescapable result of Adam's first sin in the garden.