The Gaia hypothesis is a recent and controversial theory that views Earth as an integrated, pseudo-organismic entity, and not as a mere physical object in space. Gaia, Earth, was believed by the ancient Greeks to be a living, fertile ancestor of many of their important gods. The Gaia hypothesis suggests that organisms and ecosystems on Earth cause substantial changes to occur in the physical and chemical nature of the environment, in a manner that improves the living conditions on the planet. In other words, it is suggested that Earth is an organismic planet, with homeostatic mechanisms that help to maintain its own environments within the ranges of extremes that can be tolerated by life. According to the Gaian hypothesis, evolution is the result of cooperative, not competitive processes. The Gaian hypothesis holds that evolution of life on Earth was enhanced by two processes: sexual reproduction, which...