"When Arnold wishes he had more information for his family tree, Ms. Frizzle revs up the Magic School Bus and the class zooms back to prehistoric times. First stop: 3.5 billion years ago! Luckily Ms. Frizzle has a plan, and the class is right there to watch simple cells become sponges and then fish and dinosaurs, then mammals and early primates and, eventually, modern humans. This is the story of a species, of our species, as only Ms. Frizzle can tell it"--