The Gaia Hypothesis

The Gaia Hypothesis

In the early 1960's, James Lovelock was invited by NASA to participate

in the scientific research for evidence of life on Mars. His job was

to design instruments, capable of detecting the presence of life,

which could be sent on a spacecraft to Mars.

This led him to think about what constitutes life, and how it can be

detected. He decided that the most general characteristic of life was

that it takes in energy and matter and discards waste products. He

also reasoned that organisms would use the planet's atmosphere as a

medium for this cyclic exchange, just as we breathe in oxygen and

expel carbon dioxide.

The atmosphere of Mars, like Venus, was about 95% carbon dioxide, with

some oxygen and no methane. The Earth was 77% nitrogen, 21% oxygen,

and a relatively large amount of methane. Mars was chemically dead;

all the reactions that were going to take place had already done so.

The Earth, however, was far from chemical equilibrium. For example,

methane and oxygen will react with each other very easily, and yet

they are both present in the atmosphere.

Lovelock concluded that for this to be the case the gases must be in

constant circulation, and that the pump driving this circulation was

living organisms.

It was life processes (respiration and photosynthesis), the cumulative

actions of countless organisms, that were controlling the atmosphere.

Looking at the Earth as a whole or from outer space, the mass effect

of these processes was that the Earth itself appeared as a living

entity - especially in comparison with its dead neighbours like Mars

and Venus.

Lovelock realised that the Earth coul...

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...ome of the more poetical thoughts of the originator of the


At the end of Chapter 1 in his first book, Lovelock writes:

"If Gaia exists, the relationship between her and man, a dominant

animal species in the complex living system, and the possibly shifting

balance of power between them, are questions of obvious

importance...The Gaia hypothesis is for those who like to walk or

simply stand and stare, to wonder about the Earth and the life it

bears, and to speculate about the consequences of our own presence

here. It is an alternative to that pessimistic view which sees nature

as a primitive force to be subdued and conquered. It is also an

alternative to that equally depressing picture of our planet as a

demented spaceship, forever travelling, driverless and purposeless,

around an inner circle of the sun."

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