The Gaia theory, originated by Dr. James Lovelock, purports that Earth is a single, self-regulating system.
The notion began during a consulting contract with NASA: The project was to develop methods for detecting life on Mars.
Lovelock observed that in the Mars’ environment all oxygen had combined with iron to the lowest chemical energy level, hence the red color.
Wondering why this was not the case on Earth, he concluded that there are a large number of feedback systems between living organisms and their environment which, by natural evolution, tend to produce and maintain the optimum environmental conditions for life; this includes high levels of free oxygen.
In other words, according to Lovelock’s Gaia Theory, the conditions that allowed life on Earth could not just happen naturally: Life itself was involved.
GAIA Theory: Modeling Daisyworld
Not everyone was convinced, particularly the scientists, and more particularly the Darwinists who purport that the strongest survive through natural selection. In response, Lovelock developed the Daisyworld model; a theory of evolving life on Earth that incorporated natural selection with a sentient life-force. Basically, Daisyworld was a computer model of a hypothetical planet with characteristics similar to Earth, including a rising input of solar heat.
First, scattered evenly on the hypothetical planet’s surface were the seeds of only two species: readily heat-absorbing black daisies plus heat-reflecting white daisies. Initially conditions were generally cool but less so at the equator. Black seeds, with the advantage, germinated.
As solar input rose, the black daisies spread away from the equator and ended up surviving only near the poles; the rest of the surface was covered by the highly reflective white daisies. Surface temperature was initially increased by the absorptive black daisies, and then stabilized for a long period by increasing concentrations of the heat reflecting whites. Eventually, however, the increasing solar heat was too much for even the whites; these died and the planet became too hot for life to exist.
Accepting the Gaia Theory
In 2004, MIT Press published a book entitled Scientists Debate Gaia. This book discussed such topics as:
- The compatibility of natural selection and the Gaia processes;
- Gaia and the thermodynamics of life;
- The role of computer models in Gaian science (from James Lovelock’s famous but controversial Daisyworld to more sophisticated models that use the techniques of artificial life);
- Pre-Socratic precedents for the idea of a Living Earth; and
- The climate of the Amazon Basin as a Gaian system.
One of the first to endorse the book was Jared Diamond, Professor of Geography and a geographic determinist, at the University of California, Los Angeles.
As Professor Diamond put it, the book “is a superb collection covering what has become a major scientific field. It marks the evolution of the Gaia hypothesis, from a warm and fuzzy, flowers-in-the-hair concept with vaguely religious connotations, to a well-defined and increasingly quantitative theory. The papers in this book show that the theory is becoming applicable to problems of the real earth, such as deforestation, global warming, and desertification.”
Living Earth Theory: Hypothesis, Theory, or Metaphor
In spite of all of this, the theory still remains controversial. There is, however, some well known observational evidence to support the theory of a Living Earth:
- There has been a 25% increase in heat from the sun since life began, but surface temperature has remained approximately constant.
- The present highly-unstable mixture of reactive gases (79% nitrogen, 20.7% oxygen, 0.03% carbon dioxide with traces of methane and other gases) could not be maintained without constant replacement or removal by the biota.
- Ocean salinity has maintained at about 3.4% for billions of years. Cells cannot tolerate salt concentrations much above 5%; salinity is at least partly controlled by evaporate beds/lagoons where marine life causes limestone deposits, later buried.
But the key to the Gaia theory of Earth as a Living Organism may lie in the Sulfur cycle.