Early Life: Evolution on the PreCambrian Earth, Second Edition offers an informative and compelling analysis of microbial evolution, often overlooked as the opening chapter of life's history. With this long-awaited new edition, Lynn Margulis and Michael Dolan integrate new discoveries from the past two decades, such as the enormous contribution of molecular biology, especially the accumulation of protein and DNA sequence information upon which the Woese three-domain system is based. Yet the prokaryotic-eukaryotic distinction remains the largest evolutionary discontinuity in life on Earth.