Microbes have been the dominant life form throughout Earth's history. Eukaryotes and animals evolved only after microbes evolved oxygen-generating photosynthesis.
Dr. Knoll takes viewers on a tour of the life forms that have existed on our planet since its origin. The history of animals etched in the fossil record represents merely the most recent 15 percent of the entire history of life on Earth. The deeper history and the greatest diversity is microbial. Dr. Knoll also discusses his exploration of possible life on Mars, research that draws on images of ancient sedimentary rocks collected by the NASA rover Opportunity.