"Sam: So how much of the mythology of the show that was not covered in the actual context of the series will be explained further in the encyclopedia, such as where the statue came from? Will we have more mysteries answered by this encyclopedia?" - Interview with Paul Terry and Tara Bennett
Looking through the Lost Encyclopedia, I believe it confirms that Egyptians DID build the statue of Taweret, the Temple, and the Lighthouse. I'm deducing this based on the statements "the ancient Egyptian inhabitants who built epic island landmarks like the Taweret statue." (pg. 350) and "The Lighthouse... was built by the same inhabitants of the island who built the Tempe and the Taweret statue." (pg. 218)
I know the identity of the ancient builders has always been debated and always left at "unknown", but since this is canon, I think it's quite concrete that they were Egyptians. No age for the structures is given though.
Anyways, I thought I'd throw that out there so that anybody can start editing things from "unknown inhabitants" to "Egyptian inhabitants".