In the beginning, Adam and Eve were created with the ability to make decisions and to choose their own actions. There was no evil at that time, so they did not understand evil or its consequences; they only knew good. God knew that Adam needed to learn to exercise his free will in obedience to His righteous standards. So, God permitted Satan to test/tempt them (James 1:13). God explained that if they were to eat of the Tree of Knowledge of Good and Evil, they would die (Genesis 2:16,17). They did disobey, before they had any children, and they did die. Sinfulness and evil continued in their children (Romans 5:12). Psalm 51:5 tells us, "Behold, I was brought forth in iniquity, and in sin did my mother conceive me." All people were born sinners.
Why did God do this? Is it fair for God to punish us for what our ancestors did? The apostle Paul explains in Romans 11:32, “For God has shut up all in disobedience so that He may show mercy to all.” How does God allowing evil show His mercy to all?
There are two keys given to us in 1 Timothy 2:5,6, which says Jesus “gave himself a ransom for all,” and that this ransom will be “testified in due time.” The Greek word translated ransom is “antilutron,” which means a corresponding price. Since Adam was created a perfect human being, the only price which could correspond as a ransom would be another perfect human being, i.e., Jesus. Jesus died and took Adam’s punishment in the grave. 1 Corinthians 15:22, "as in Adam all die, so also in Christ shall all be made alive." Since all were in Adam when he sinned, then when Jesus took Adam's place in death, that included all who were in Jesus. God's mercy, and His wisdom set it up this way so that only one ransom would be needed for all who sin.
The second key from 1 Timothy 2:5, 6 is that this will be testified in due time. The results of that ransom guarantee that all are to be made alive in God's Kingdom. There is the due time or “day (period) when he will judge the world in righteousness” (Acts 17:31). Yes, during the resurrection, mankind will learn righteousness. “No longer shall each one teach his neighbor and each his brother, saying, ‘Know the LORD,’ for they shall all know me…For I will forgive their iniquity, and I will remember their sin no more” (Jeremiah 31:34). After the “judgment day,” when people who now only know evil will experience only good, there will be another test, called the Little Season (Revelation 20:3). All who then choose evil, knowing both evil and good, will die the second death and never live again. All who choose good (most people) will live forever in peace and love, just as God had planned from the beginning.