Scientist James Lovelock's Gaia hypothesis met a hostile response in 1979 but, with the publication of his autobiography next week, it seems events have borne it out. Tom Wakeford reports

Anyone who talks to James Lovelock, now 81, soon becomes aware that he is no ordinary scientist. While others toil in universities and corporations, Lovelock has spent the past 38 years deliberately detached from academic and other research institutions. His house and laboratory nestle together in a converted water-mill on the edge of Dartmoor, an hour's taxi-ride from the nearest station, and he does not normally use the telephone.

Yet he is also someone deeply in touch. When I arrive at his house with mud on my trousers, he points out that the state of his footpaths is the result of the neighbouring farmer planting European Union incentive-scheme maize, an utterly inappropriate crop for the soil. The valuable top-soil has been washed onto his woodland. Later, when a shower falls on the hot, dry earth around his house, producing that characteristic odour of summer rain, he discusses theories that the chemical responsible for the smell is a terpene, probably emitted by bacteria that inhabit the surfaces of rocks.

Lovelock's wooded idyll is a long way from Brixton in south London, where, as he describes in his autobiography, Homage to Gaia, he was raised as the only child of working-class parents between the wars. He was educationally precocious and learnt more from the books he read in the public library than he did at school. His scientific horizons were also expanded by close contact with the Leakey family, which was related to his mother's family by marriage.

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Lovelock's first job was with a firm of photographic chemists in Pimlico. They insisted that he take evening classes for a chemistry degree and imbued in their young trainee an abiding passion for accurate measurement, rather than the fudging of results that Lovelock claims is "so normal" in a university training. He became known for his uncommon ability for trouble-shooting in experimental procedures. Later, at Manchester University, where he was evacuated when war shut London's academic institutions, he was accused of cheating for obtaining such perfect results in chemistry practicals.

Wartime Manchester was also where Lovelock's Quaker values became apparent. He registered as a conscientious objector, even though as a full-time science student he did not have to, and appeared before a tribunal. In 1944, he felt driven by the sacrifices being made by his peers to abandon his "conchy" status and sign up as a medical orderly. But two days before he was due to report, his director, unwilling to lose a key member of staff, had the order cancelled.

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The moral basis of Lovelock's scientific research and his commitment to being a "witness to truth" are themes throughout his career. His autobiography acknowledges that he, and those who worked with him, had no idea of the consequences of their work, but it poignantly charts the way in which his 1950s research contributed to the industrialisation of agriculture, and he mourns the consequent loss of countless human-crafted agro-ecosystems.

Central to Lovelock's unique ability to take an overview of life on earth is his breadth of knowledge and experience in an extraordinary range of disciplines. To earn his keep while at college, he took work on a farm in rural north Lancashire. At the Medical Research Council's National Institute for Medical Research at Mill Hill over the next 20 years he must have gone through every division of the institute: "Chemistry, biophysics, experimental biology, virology, physiology, you name it," he says. He also assisted an oceanographic voyage aboard HMS Vengeance and spent a year at the Common Cold Research Unit.

Although his main job at the MRC was in-house inventor, Lovelock made the most of the opportunity to work with and learn from many of the great scientists of the 20th century - Mill Hill in London housed five Nobel prizewinners in the neighbouring laboratories. "You have to learn the languages of each discipline," he says. "It gave me a chance to get a view across science."

He was 25 when his first paper in Nature was published, and his inventions, including a prototype microwave oven and the electron capture detector, were the pioneering products of Mill Hill's scientific melting-pot.

Then, in 1961, Lovelock received the invitation from Nasa that allowed him to go it alone. His main contract was as a consultant at Nasa's Jet Propulsion Laboratories in California, where interdisciplinary teams of physicists, chemists and biologists were designing experiments to test for the presence of life - first on the moon, then on Mars. Lovelock questioned the assumption underlying the experiments, which was that life on other planets would have a similar form to that of organisms on earth.

Soon word got around that Lovelock was unimpressed with Nasa's approach. "The biologists asked, 'Who is this bugger? He's just meant to be inventing devices for our experiments'." He was hauled into the senior researcher's office and given two days to come up with his own idea as to how life could be detected on other planets. His answer was based on the reduction of entropy in a planet's atmosphere. If such an atmosphere contains compounds that are unstable together, a living system is likely to be involved in production of them. It drew on ideas confirmed by his re-reading of Erwin Schrodinger's 1945 book, What is Life?.

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The proposal thrilled his boss, was written up immediately in Nature, led to a technique that Nasa still uses today and, a few months later, in September 1965, inspired Lovelock to conceive of the Gaia hypothesis.

When Lovelock first mentioned the hypothesis to his colleagues, few saw its radical implications. It was not until 1970 that he found the young biologist Lynn Margulis, who had the imagination and vision to develop the concept with him. "She put flesh on my bare bones of Gaia," he says. Together they published two ground-breaking papers on the hypothesis in 1972. Their work, which presented the global atmospheric system as if it were a living organism and, even more radically, attributed purpose to such a being, became the subject of furious debate when it appeared in 1979 in the book Gaia: A New Look at Life on Earth.

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The name for Lovelock's hypothesis was proposed by William Golding, author of Lord of the Flies, who had been a neighbour of his. Gaia, or Gaea, is the ancient Greek goddess of the earth. But Golding's suggestion carried with it the implication that the earth was not just another object or system, but an integrated whole that should be the subject of awe and reverence. It was the name, more than the ideas the hypothesis expressed, that seemed to annoy many scientists, especially evolutionary biologists.

Richard Dawkins devoted a chapter of his 1982 book The Extended Phenotype to trashing Gaia, while Lovelock's colleagues, including fellow members of the Royal Society, ignored it. "It was partly my fault - I was too shy and thought the big names at the Royal Society such as John Maynard Smith would not be interested," he says. The two men are now great friends and Maynard Smith supports the theory, if not the name.

But many other thinkers, especially those attempting transdisciplinary studies of life and the environment, welcomed Gaia. Philosopher Mary Midgley hailed it as a breakthrough - "the first time a theory derived from scientific measurements has carried with it an implicit moral imperative - the need to act in the interests of this living system on which we all depend". Whatever scientists think of Lovelock and the name he gave his theory, few would deny that its key insight, that life is, and has been, the main influence on earth's climate over the past 4 billion years, has been borne out.

Gaia entered popular discourse via its adoption by the green movement during the 1980s. Lovelock has inspired and remains friends with environmentalists such as Jonathon Porritt and Sir Crispin Tickell. Yet his strongly held views on the science of the environment have left some of his green supporters confused and sometimes hostile. One mistaken interpretation of Gaia theory is that it encourages industries to pollute, because the global ecosystem will use homeostatic mechanisms to stop such phenomena as global warming. But Lovelock has repeatedly said that the rate at which human activity is changing the climate is so high that the earth's regulatory system could react by moving to a state that threatens human existence.

After a period of particularly virulent criticism, Lovelock wavered in his use of the term Gaia, but he is now glad he stuck with it. "The Gaia book may have harmed my relations with the Royal Society and the establishment, but as to educating other scientists and the general public, it has done a tremendous amount of good," he says. Embracing Golding's imagery of Mother Earth, he ends his book: "I know I am part of her, and that my destiny is to merge with the chemistry of our living planet."

Homage to Gaia is published on Thursday by Oxford University Press, Pounds 19.99. It will be reviewed in next week's THES.

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