The Man From Earth (2007) was really a good movie but what I quite didn't understand the end, why does Dr. Gruber die at the end and did it prove that John was God?
Dr. Gruber died of a heart attack after the shock of learning...
...that John Oldman is his father.
This does nothing to prove that John is God. It does lend a small amount of credence to John's story, since he knew details about Dr. Gruber's father. However, John only led the group to believe that he was the inspiration for the story of Jesus, not that he was in any way God.
This is what I think of the end : The girl ( Sandy ) asked John a deliberate question at perfect timing to exploit the heart medical condition weakness of the psychology professor Freud. I thought that this " question was even worth asking ? " as its answer provides no good information to the questioner. That's why I thought it as a deliberate question like she was working with him so he can approve of her moving with him as she wants cause she loves him. Her statement to the john when the professor died: " you have never seen old grown boy death " also reflect the story been made up. In the end, she moves towards to his car as he accepts her observation and help and ready to take her with him. The psychology professor was a growing threat as he wants to examine the John. There were some other hints also. But the question arises:" Why he made up the story? ".