This is the sixth in the great series of essays that the world's best science writer has produced. They range over a vast field, from history to the latest theories in biology, from controversies over palaeontology to the origins of language.

No one illuminates the wonderful workings of the natural world as perceptively and enjoyably as Stephen Jay Gould. In this volume of reflections on biology, history and culture, Gould addresses the burning issues of ecological crisis and contemporary species extinctions as well as giving us fascinating insights into evolution - such as the fact that the first land vertebrates had up to eight toes on each foot, and that the ichthyosaur had a very significant kink in its tail.