    Sentence 1: Just when you thought it was  safe to assume that we now know all we  are ever likely to know about the past,  someone digs another hole and unearths  (literally or figuratively) some ancient one  day it is a fragile scroll, found in a cave  near the Dead Sea, that turns out to be  pre-Biblical; the next day it is an entire  terracotta army of Chinese the next a  skull, excavated from the Olduvai Gorge,  that compels anthropologists (once  again) to revise their guesses about the  earliest stages of Homo sapiens sapiens  vs hominids.                   