Any consideration of the geological history of earth as it pertains to the genesis and evolution of life, that is, to paleobiology, must hold the sea as centric. Life began in the sea, and most extant life yet exists in the sea. The sea contains an incomprehensible diversity of life, mostly still undiscovered or described, ranging across all the domains of life. The sea is absolutely brimming with microscopic life, including bacteria that make their living by a constellation of different metabolic processes, and the Archaeans, among which are the extremophiles living in vents at temperatures well above the boiling point of water.