Definitely had him in mind when I mentioned Indo-European myth! One very interesting take on this "very old" hypothesis is Tom Rowsell's shortish documentary "The World's Oldest Myth? World Tree and Reincarnation Documentary": https://www.youtube.com/watch?v=exlcT_iL9-U

He doesn't touch on the Egyptian connection at all, and he presents some of his claims as more definite than I think they warrant, but it's certainly fascinating.