With verve and clarity, Isaac Asimov guides the reader to an understanding of how our concept of heredity has changed with each new piece of evidence uncovered in the last century. We learn about the plant-breeding experiments of Gregor Mendel, and the discovery of mutations and chromosomes. The book ends with a discussion of the use of X-rays to produce mutations and the effect of natural mutations on the evolution of species.

This isn’t a particularly outstanding member of the “How Did We Find Out” series, although there’s nothing wrong with it. Chapter One is basically Asimov’s “Mendel talk” written up for youngsters, but since Asimov also wrote up his “Mendel talk” elsewhere for adults, there’s no reason for adults to read this book just for that. Otherwise, it’s a good exposition of inheritance, genes, and natural selection.

(Asimov’s “Mendel talk” was one of his standard talks which he gave over and over, describing the dramatic story of how Mendel discovered the laws of inheritance, how von Naegeli tossed his work aside and drove it to obscurity, and how it was discovered a generation later by three botanists who all had the scientific scruples to give Mendel priority for their independent discovery of his work. Asimov’s telling is, perhaps, a little overly dramatic, but it is a dramatic story and well illustrates Asimov’s ideal of scientific ethics.)