This is the fourth volume in Asimov's "How Did We Find Out. . ." series which aims at reader participation in the process of discovery, but there is nothing in his lackluster survey of fossil finds and dinosaur features to stimulate any kind of mental activity. The first half of the book, which doesn't mention dinosaurs, skims through some landmarks in natural history from the 1500's on (Gesner -- "the first man to draw pictures of fossils," Bonnet's disaster theory to reconcile fossils with the Bible, Linnaeus' system of classification, Darwin's theory of evolution) and might have better been entitled "How We Found Out the Earth Wasn't Created in Six Days." The pages on dinosaurs themselves, after the usual mention of Mary Anning who found the first ichthyosaur and plesiosaur remains, is simply a rundown on the size, names, build and eating habits of a few of the better known species -- and as such surely superfluous.