Why do elephants have big ears? Why do shrews have large hearts? Why don't gnats get wet when it rains? And why are there no snake-shaped mammals? This highly readable popular science book engages the reader with a variety of such puzzles and conundrums to explain how creatures have interacted with their environment to evolve into the extraordinary forms they possess today. Lavers makes use of biology, physiology, zoology, ecology, and palaeontology in order to arrive at his explanations. In the process, he explains such things as how warm-bloodedness evolved and why mammals dominate continents and amphibians cool, damp places; and he concludes by presenting a new view of life on earth, rejecting all notions of superiority and inferiority in nature.