Gaia or "Gaea"

(pronounced "guy-uh")

In Greek mythology, Gaia was the personification of Mother Earth, and the daughter of Chaos, who bore and married Uranus and became the mother of the earliest living creatures: the Titans; the Cyclopes; and the Giants, or Hecatoncheires (Hundred-Handed Ones).

Leave it to the Greeks to create a "god world" as complex as the Earth itself.

In the 1970s the British scientist James Lovelock, along with the American biologist Lynn Margulis, formulated the Gaia hypothesis, which has attracted many followers. According to this theory, the planet behaves like a single living organism. Lovelock postulated that the earth, like many organisms, can regulate its temperature, dispose of its wastes, and fight off disease. These physical conditions of the Earth's surface, have been made fit for life and maintained by the biota themselves.

Evidence includes the relatively constant temperature of the Earth's surface that has been maintained for the past 3.5 billion years despite a 25 percent increase in energy coming from the Sun during that period. The remarkable constancy of the Earth's oceanic and atmospheric chemistry for the past 500 million years also supports this theory.

As Lovelock put it, this is "a new insight into the interactions between the living and the inorganic parts of the planet. From this has arisen the hypothesis, the model, in which the Earth's living matter, air, oceans, and land surface form a complex system which can be seen as a single organism and which has the capacity to keep our planet a fit place for life."

When the public first heard about Gaia in the 1970s, it liked the message. At a time when people could talk about the Age of Aquarius without grinning, the notion of Earth as a single living being, not quite what Lovelock proposed, but not inaccurate either, seemed to fit. Academic scientists, on the other hand, were not impressed. And the quasi-religious name didn't help. But worst of all was the concept itself—the Earth in some way alive?

Of all those who objected to the idea, no group was more vehement than evolutionary biologists. They don't believe in free lunches. They believe creatures are out to help themselves and their relatives to survive, not to help strangers. The idea that some creatures waste effort making the world a better place for others didn't make sense to them. As for global self-regulation, the complex physiological systems of living beings do not come about by chance. They evolve. Many different versions are tried out; only the best leave descendants. That's natural selection. And natural selection cannot apply to a whole planet, which has no competitors or ancestors.

For the hard core, Gaia is about biology, not earth science or complex systems. Their battle cry is symbiosis, the many varied ways that creatures have of coming to depend on one another. That's something Gaians think traditional evolutionary biologists don't know how to deal with. But scientists are beginning to agree that there seem to be long-term stabilities in the environment that may have underplayed. The power of computers to create realistic and robust simulations has served to bring Gaia a new respectability.

Today, 30 years after Lovelock gave his first seminar on the idea to a nonplussed audience in Princeton, New Jersey, Gaia has made some progress. While to many mainstream researchers Gaia remains out-of-bounds, some ideas that flowed out of Lovelock's Gaian thinking have been proven correct, even if their provenance is forgotten or hushed up. And a growing number of scientists have decided to center their work on the Gaian concepts. But even among believers, there's no real consensus as to what Gaia is or how it really works.