Berger's primer-like explanation of how different species come to be begins with the familiar house cat (""about 50 different kinds"" but all one species), introduces other members of the cat family, and shows how one original cat species, with a range of individual characteristics, gradually spread out and changed, over the generations, to fit into different places. Then she switches abruptly to bears and how they branched out during the Ice Age, and then to camels whose spread was affected by other ""land changes."" (Interestingly, camels ""started out"" in North America but became extinct on their home continent.) Berger ends with people, emphasizing that there is only one human species though individuals vary and groups' skin color has changed according to the amount of sunlight in the areas they moved to. One might wish for a little style and imagination in the presentation, but as a simple introduction to the origin of species, and the concepts of species and family, it is clear and sound.