H. Beam Piper 
Genesis [EPUB ebook] 
With linked Table of Contents

Was this ill-fated expedition the end of a proud, old race—or the beginning of a new one? There are strange gaps in our records of the past. We find traces of man-like things—but, suddenly, man appears, far too much developed to be the “next step” in a well-linked chain of evolutionary evidence. Perhaps something like the events of this story furnishes the answer to the riddle.