Gaia Original Versions

In the late 1960s, James Lovelock was working for NASA on life detection methods for Mars. With his chemistry training, this experience caused him to think deeply about what makes Earth different from Mars or her other neighbors in the solar system and the role that life might be playing in those differences. The imprint that life leaves on the chemistry of our own atmosphere stood out as a significant fingerprint of Earth's ecosystems. These musings led to the formulation of the first incarnation of the Gaia hypothesis. The early notion advanced by Lovelock is summarized in his 1972 paper, ''Life regulates the climate and the chemical composition of the atmosphere at an optimum for itself.'' Novelist William Golding, who lived near Lovelock, suggested naming the idea after the Greek goddess. This was lovely and poetic, but probably contributed to early perceptions that the concept was cultic or New Age, not scientific.

After significant initial criticism, Lovelock and Margulis realized the flaws in the initial version that laid them open to criticism. Biologist Ford Doolittle was particularly helpful in pointing out that the hypothesis as stated required foresight and planning on the part of collections of organisms toward a common goal. This appeared to be a teleological (purposeful or designed) notion that is not in keeping with the scientific view of causality.

Later, the revised formulation appeared in a number of written and oral presentations that can be paraphrased as: ''The whole system of life and its material environment is self-regulating at a state comfortable for the organisms.'' This was eventually restated by Lovelock in 1988 in his book The Ages of Gaia as ''Living organisms and their material environment are tightly coupled. The coupled system is a superorganism, and as it evolves there emerges a new property, the ability to self-regulate climate and chemistry.'' Lynn Margulis, the innovator of the endo-symbiotic theory of eukaryotic cell origins, emphasizes the role of symbiosis in biology. Her statements about Gaia usually include the phrase superorganismic system. In her view, evolution is the result of cooperation, not competition, and this is in keeping with the Gaian interpretation of global ecology.

(reinforces external changes)

Examples: Melting snow over dark soil Population growth

(reinforces external changes)

4-1

Feedback increases input

1-,

L

L

I

1

1

Input

System

Output

L

. Feedback reduces input

Negative feedback loop (diminishes external changes)

Negative feedback loop (diminishes external changes)

Examples: Toilet float tank Thermostat

Figure 1 Logic of negative and positive feedback loops.

The initial conception involved the idea of homeostasis, that is, regulation around a narrow range of physical variables and resistance to perturbation via cybernetic feedback loops. However, Margulis particularly argued that Gaian systems are rather homeorhetic, meaning that the Earth's atmosphere, hydrosphere, and lithosphere are regulated around set points that can change in time as the whole system evolves essentially through a life cycle. The basic logic of negative and positive feedback loops is illustrated in Figure 1.

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