It says so in the Bible.
To eat the forbidden fruit was the ONLY thing that Adam and Eve could have done to go AGAINST God. They could have swore, told dirty jokes, drank beer and whiskey. Maybe one could have physically abused the other or abused the animals. They could have had Cain and Abel and one still killed the other, but we would still be in paradise.
That said, the horrible incidents would not have happened because sin would not be in their nature. They and us would have a SINLESS NATURE and joyfully live with God on Earth forever in our physical bodies.
Adam and Eve had domain over heaven on Earth living with God and they did, but it was short-lived. Do I wish ill will FOREVER on Adam and Eve and not forgive them? It's TEMPTING as we don't know what happened to them.