The most likely central idea of the given passage is that <u>Marlow believes he and his crew have literally time-traveled to the Stone Age.</u>
According to the given passage, the narrator talks about his journey with a group of people who were wanderers on a prehistoric earth and fancied themselves to be conquerors, taking possession of that place.
In Heart of Darkness is a story told about Marlow who journeyed to Congo, Africa and he has a twisted concept of reality where he believes he has literally gone with his crew to the Stone Age.
