Why was the olmec civilization unknown to the modern world until the late 1850s?

The location where it was discovered is a dense jungle with less people. The civilization disappeared without trace and there was few written history about it.  even the available writings are still undeciphered. before then a lot of intrest was in Aztec which had already been accepted as the predominant ancient civilization.

One key element is humour! the man probably represents a politician or worker!

The answer is c socialist