This book presents a history of the last two centuries of biology. It covers early evolutionary biology — Lamarck, Cuvier, Darwin, and Wallace through to Mayr and the neodarwinian synthesis — and also discusses social implications, the struggles with our religious understanding, and the interweaving of genetics into evolutionary theory. The book's account is an integration of the cytological tradition and the new understanding of the diversification of life coming from comparative analyses of complete microbial genomes. The book includes the history of research and theories about symbiosis in evolution, research on microbial evolution, bacterial evolution, and symbiosis in evolution.