Why are all the big land animals on Earth mammals? Why are reptiles so small today when they were so huge in the Age of Dinosaurs? Why are rivers, lakes and swamps dominated by large cold-blooded reptiles and not by mammals? Why are there so many birds on Earth and why are they all so small? In this beautifully written and utterly compelling book Lavers scours the fields of biology, physiology, ecology and palaeontology to find answers to these global-scale questions. In the process he reveals a fundamentally new view of life on Earth, one that offers no room for notions of superiority and inferiority in nature. 'If you want to understand evolution, read this' David Bellamy