In the early 1960s, Chan Thomas wrote a book titled The Adam and Eve Story and attempted to have it published by Emerson House in Los Angeles. Soon after publishing the full issue, the CIA classified his book for 50 years. An FOIA lawsuit was filed against the CIA to release the book. In 2013, the CIA released a "cleansed" version of the original book (50 pages out of 240 original pages).
Why was this book classified?
https://www.cia.gov/readingroom/docs/CIA-RDP79B00752A000300070001-8.pdf
Depending on how outlandish you are feeling, this is an interesting story. I've no idea if the Burrows Cave Illinois finds are legit, wiki says not (but it would).
https://en.wikipedia.org/wiki/Burrows_Cave
This guy Alex has done some research on a civilisation he believes are connected with these objects. Combined with various other disciplines including language and resonance he makes some quite startling discoveries. (this does connect with the 12,000 cycle theory)
http://www.human-resonance.org/sanskrit.html
http://www.human-resonance.org/illinois_archive.html
http://www.human-resonance.org/illinois_archive2.html
http://www.human-resonance.org/mediterranean.html
Etc through the site, it's all fascinating.
This is a fascinating topic. The eye of the Sahara aka the Richat Structure is theorized to be Atlantis. Wiped out around 12,500 years ago. Awesome topic to discuss, pyramids etc.