How much of a surprise was the twist in 1968?

I was born in 1968 - so obviously I don't remember what people thought of the twist of The Planet of the Apes actually being Earth at the time.

I first saw the movie on TV when I was about 13. I thought it was a good movie - but I also remember not being terribly shocked by the ending. Particularly because they made such a point to say the astronauts had awoken in the distant future - and because in the 60s and 70s pretty much EVERY movie set in the distant future had mankind's Earth getting it's *ss handed to it in some way or another. If we hadn't blown ourselves up in a nuclear war, been taken over by pale-skinned vampires in over-sized Jawa hoodies, or found out our favorite candy bar was made out of people - we would have at least been enslaved by apes. By the time Chuck and co. found the talking doll, I remember thinking he had to be pretty thick if he didn't see it coming that he was in fact on Earth - especially since he had recently starred in so many other end-of-the-world movies.

However, I may have at some time in my early childhood seen the Statue of Liberty scene without fully processing it - but remembering enough of it subconsciously to know what was going to happen by the time I watched the entire movie. In retrospect it was pretty obvious that Bruce Willis was a ghost in The Sixth Sense - but I admit I definitely didn't see that coming at the time.


So - how big a surprise was the ending in 1968? Were people in the theater genuinely surprised?