In 1978, James Lovelock, an independent British inventor of scientific equipment, proposed that the Earth was a unified living system, which he called Gaia. The Earth did not just have organisms living upon it, but could be thought of as an organism in its own right. It had physiological processes that regulated its internal conditions, just as an organism does. One of the first biologists to join him in this viewpoint was Lynn Margulis, who was famous for having figured out that complex cells evolved from the merger of simpler cells. Simple cells merged together to form complex cells, and complex organisms form complex ecosystems, which form the entire Earth. It is not just cells that are alive, but life exists on all these different levels.
Some animals (the homeotherms, such as humans) can regulate body temperature. Some scientists, following the lead of Lovelock and Margulis, claim that the Earth can do this also. Five billion years ago, the Sun produced less light, but the Earth was even warmer than it is today because there was a lot of carbon dioxide in the air, causing a greenhouse effect. As the Sun grew brighter, green cells in the oceans of the Earth removed carbon dioxide from the air (through photosynthesis), reducing the greenhouse effect, and keeping Earth’s temperature about the same as (even a little bit cooler than) it was before. This is one example of Earth having a type of homeostasis, or physiological regulation. Some scientists even use the term geophysiology for such processes. (Photosynthesis cannot rescue us from the greenhouse effect now occurring, simply because it is occurring too fast.)
This does not mean that the Earth has intelligence. All it needs is negative feedback processes. If the atmosphere has too much carbon dioxide, plant cells will remove it, and if it does not have enough carbon dioxide, decomposition will produce it. No intelligence required. Of course, intelligence is not needed for most processes within animal or plant physiology. Trees losing their leaves in autumn is a physiological process involving the length of the night and a pigment called phytochrome and a shift in hormone production, all of it accomplished without brains.
The Gaia viewpoint continues to reside on the fringes of scientific thought, often because scientists take it too literally. Some dismiss it because they think Lovelock and Margulis literally believe the Earth to be a goddess, when in reality they use Gaia as a metaphor. But every year more scientists accept some version of the Gaia concept, once they realize that it is a system of negative feedback processes rather than a goddess. It may have been unfortunate for Lovelock to have chosen the name Gaia; then again, who would have noticed the concept if he had written about the Earth as an integrated set of negative feedback processes?
So, if I were a scientist with a reputation for big-time highly-funded research, I might hesitate to use the word Gaia in public. But since I am a science educator and writer (and I do research also, on the cheap) who wants to get people to grasp the major concepts of the way the world works, I decided to go ahead and throw my hat in the ring with the Gaia theorists. Once my book Life of Earth: Portrait of a Beautiful, Middle-Aged, Stressed-Out World comes out later in 2010, there will be no turning back. I had to write the book in a hurry, without sitting around and wondering about my reputation. Too late now; the book is in production. But I don’t think I am going to regret my decision.
A version of this essay has also appeared on my website.