The History of Life: Spontaneous Generation The Earth before Life The Origin of the First Cells Early Life Forms The Evolution of Multicellular Life The Fossil Record Evidence from Modern Organisms The Theory of Evolution: Early Evolutionary Theory Darwin's Voyage Darwin's Theory Mechanisms of Natural Selection Population Genetics Speciation Plate Tectonics, Continental Drift, and Biodiversity Human Evolution: Primates Primate Evolution Early Hominids Homo sapiens