Why didn't Jesus teach about Adam's sin affecting the whole human race?
Jesus did not teach the ramifications of Adam's sin affecting the whole human race because He was waiting for the revelations given to the apostle Paul. While He taught that all were sinners, He did not tie that truth back to Adam as Paul later does, making it plain.
Les teaches that Jesus never mentioned this truth, and he suggests the reason is that Jesus was going to wait for the revelations given to the Apostle Paul. Jesus never taught, as far as Les is aware, the ramifications of Adam's sin and how it carries over into the whole human race. Jesus certainly taught that all were sinners, but He did not tie it back into Adam like Paul does. Nowhere else in the Old Testament is it taught. Paul bridges this information, and it is laid out as plain as day.
Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned:
More Questions
Did Jesus teach that everyone is a sinner because of Adam's sin?
Although Jesus certainly taught that all people are sinners, He never taught that sin ties back to Adam and carries over into the human race in the way Paul does.
Why is Adam blamed for sin entering the world instead of Eve?
In Romans 5:12, the 'one man' who brought sin into the world is Adam, not Eve, so the blame is laid on Adam, not Eve.