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! There aren't any people around to ask for directions. 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. It's the longest class...

"Sex Cells is the tale of scientific stonewalling, intrepid advocacy, and the still-pitched battle to get the scientific and medical world to recognize that women are not small men. Phyllis Greenberger has been working in the field of biological sex differences for more than 30 years, and she continues to be struck by the lack of understanding about this topic, even among medical professionals. After all, it's a fundamental aspect of human life: males...