Chapter Three, Explosion of Life, traces the evolution of life from the “small shelly fossils” of the Lower (early) Cambrian to the dinosaur’s demise at the end of the Cretaceous. More evolution occurred during this 477 million years than during the entire preceding two billion years. Major evolutionary events such as the duplication of the entire genome during the Silurian or late Ordovician Period; the movement of life such as the first vascular land plant, Cooksonia, onto land during the Silurian Period; plant’s development of the seed habit; reptile’s development of the egg; and first appearance of mammals are briefly noted. The six major mass extinctions, such as the end Permian “great dying,” that occurred during this time are included.
