I don't know the origin, but I do know "6,000 Years Ago" by Doc Watson. I believe there's a tradition of old men spinning yarns about their huge age in various sections of North American culture. S.J. Perelman wrote a short story about having his hair cut by a barber who kept telling tall stories about the famous hair that he'd cut.

Mel Brooks used to do a comedy routine called, I think, "The 2,000 year-old man".

As for the song, "100,000 years ago" - did Elvis do a version?

Doc sings:

I was born about six thousand years ago.
There ain't nothing in this world that I don't know.
I saw old King Pharaoh's daughter pull little Moses from the water.
I can whip the man that says it isn't so.

[Chorus]
I'm an educated man, to get more sense into my head I plan.
I've been on earth so long, and I used to sing this song
While all those old-timers took their stand.

I saw Noah when he built his famous ark.
I got into it one night when it got dark.
I saw Jonah swallowed by the whale, and I pulled the lion's tail.
I can whip the man that says it isn't so..

[Chorus]

Queen Elizabeth fell dead in love with me (yes she did).
We was married in Milwaukee secretly.
Then I took her out and shook her, and I went with General Hooker
To fight mosquitoes down in Tennessee..

[Chorus]

I saw Satan when he walked that Garden o'er, (old booger)
And Adam and Eve were driven from the door.
While the apple Eve was eatine, old Adam he was a'cheatin'.
I can prove it for I'm the man that ate the core..

[Chorus]

I saw Abel when Cain hit him with a spade,
And I know the game was poker that they played.
I was hid behind a shrub when Cain slapped him with that club,
Poor old Abel caught him a-cheatin' and now he's dead..

[Chorus]