Kam Patel talks to Richard Dawkins, the zoologist who believes that one day pigs could be made to fly. Richard Dawkins laughs a little as he recalls a recent conversation he had with a colleague. The colleague, obviously possessed of a wacky sense of humour, concluded that Dawkins could be an instant millionaire if he so desired. All Dawkins had to do was suddenly to announce to the world that he had undergone a miraculous conversion to Christianity.

Given enough millions of years to play around with, Dawkins is confident that he can breed pigs that can fly. But the chances of his ever turning to God in a zillion years are zero.

With a reputation for being controversial, Dawkins, a reader in zoology at Oxford university, has been engaged for years in a running battle with the religious fraternity over the origins and development of life. The row has at times threatened to overshadow his work in modern biology, a field in which he has carved out a reputation as an influential thinker, partly on the strength of a series of bestselling books including, in 1976, the Selfish Gene. In this book Dawkins advanced the case for a "selfish" entity, the gene, that "works" to preserve and propagate itself - the claim being that the Darwinian theory of evolution via natural selection operates at the level of the gene and not at that of groups, species or individuals.

Dawkins has said that Darwinism has never been in as much need of advocacy as it is today. In saying this, he is thinking in particular of "the fountainhead of creationism" which has found a welcoming home in the United States. Yet he is encouraged by the response whenever he takes part in American radio phone-ins. "I found that people hold the erroneous beliefs that they do largely because they have never been exposed to anything else. So when I try to explain something clearly . . . the reaction is not an attack but 'Gee that's right! Why didn't anyone tell me before?'"

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Many scientists, though, are genuinely puzzled by the extent of Dawkins's embroilment in a anti-religious row. Why? Surely he is concerned that the broader scientific signals he is sending out through his books are suffering from the noise and vehemence of the argument with theologians? He recalls recently appearing on Desert Island Discs. Presenter Sue Lawley spent most of the programme focusing on his views on religion. "You see, if you say something positive like the whole of life - all living things - is descended from a single common ancestor which lived about 4,000 million years ago and that we are all cousins, well that is an exceedingly important and true thing to say and that is what I want to say. Somebody who is religious sees that as threatening and so I am represented as attacking religion, and I am forced into responding to their reaction. But you do not have to see my main purpose as attacking religion. Certainly I see the scientific view of the world as incompatible with religion, but that is not what is interesting about it. It is also incompatible with magic, but that also is not worth stressing. What is interesting about the scientific world view is that it is true, inspiring, remarkable and that it unites a whole lot of phenomena under a single heading. And that is what is so exciting for me."

There are aspects of religion that certainly annoy Dawkins - its use as a justification for wars, its interference with people's sex lives and their reproduction. He finds the Roman Catholic hierarchy's position on in vitro fertilisation "disgusting". But for Dawkins these irritations are "a separate matter from the more fundamental thing, which is a glorying, an exalting in the universe and a belief that the proper response to that is to try and understand it, and not let the sense of awe just flatten one."

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Dawkins's arguments are widely accepted within biology. But there are a few dissenters even within the field, who take issue with particular points. One such is Brian Goodwin, professor of biology at the Open University. Dawkins sums up his differences with Goodwin as centring on the relative importance of the mechanism of natural selection in the operation of evolution. Dawkins defines natural selection as "the non-random survival of randomly varying genetic instructions." In other words it is a two-stage process, the first being the production of mutations in the genes of every new generation; the second the non-random action of the environment on each individual, causing some to die, others to survive, passing their mutations on to their offspring.

His debate with Goodwin, he says, can be regarded as an argument about the relative importance of natural selection versus that of the available raw material that selection has to work with. This can be starkly illustrated by asking why, for example, pigs do not have wings. "At one extreme there would be those who say that pigs do not have wings because there never was the available raw material of genetic variation - that they never sprouted wing buds. On the other hand, I would say they do not need wings, they are better off without them." The disagreement would be more focused if an experiment were devised whereby the two were challenged to breed pigs with wings. "Brian Goodwin would say you cannot do it and I would say give me enough million years, and I'll do it."

Next month will see the publication of Dawkins's latest book on Darwinism, River Out of Eden. The use of the river metaphor is new and serves to put a time dimension on the familiar concept of the gene pool, which now becomes a slice through the river of genetic material or DNA, a "river of information" that flows through time.

A recurring feature in Dawkins's work is the use of computer metaphors to help explain his ideas, and River Out Of Eden is particularly rich in digital concepts. These parallels enable Dawkins to argue powerfully for a consideration of genetics as a system which in many areas varies digitally, in a series of discrete steps, in contrast to analog models where there is continuous change. He says: "DNA is supremely digital and I think this is really the major impact of Watson and Crick." But he does not want to stretch the digital nature of genes too far, pointing out that Mendelism is digital to the extent that a gene is either there or not there in sexually reproducing populations.

Mendelism, named after the Austrian biologist and monk Gregor Mendel, proposes that in sexually reproducing species all characteristics are inherited through indivisible "factors" - now identified with genes - contributed by each parent. Dawkins says: "You could still have done a kind of river of genes, a river of Mendelian particles. But as for the way the genes actually worked at the molecular level, that would probably have been assumed to have been analog at the time."

Dawkins stresses that genes have two broad roles: genetic and embryological. The genetic role is encompassed by genes passing through the river of time, from one generation to another: "To that extent genetics has been digital ever since Mendel. Before Mendel, genetics was analog in all its aspects."

The embryological role - the impact of genes on embryological development - is more complex but still digital in many of its aspects. It is, for example, digital right down to the basic fine structure of genes, says Dawkins. And the ribosome, the protein making machinery of the cell, behaves exactly like a digital tape reader - "the resemblance is extreme," he says.

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In the later stages of embryology as far as it is known, the system becomes analog. Once enzymes are present they govern embryological development by changing the rates at which things, largely chemical things, happen. But Dawkins stresses that even in these later stages, while rates of chemical reactions are analog quantities, they are coded by digital genes.

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The use of computer metaphors in Dawkins's work owes much to his extensive day-to-day use of computers, and he regards them as having an important influence on his thinking. A proficient programmer, he started using computers in the age of the paper tape: "You would go to a computer room and you'd be smothered by paper tape and machines chuntering everywhere. You'd feel that you were in a room surrounded by all sorts of digital machinery - translators, copiers and so on. And that is what a cell is like. A cell is a digital data-processing room filled with the equivalents of tapes and cards and bits and bytes floating around everywhere. At a poetic, metaphorical level, exposure to computers helps you to understand the world of DNA."

He has written computer programs in an attempt to simulate aspects of evolution. The Blind Watchmaker program is a model of artificial selection with randomly generated variation and a limited kind of embryology that generates forms in two dimensions. He has just completed a new program based on the mathematically rich form of snail shells and says that it has significantly improved his understanding of molluscs.

Dawkins's work has been seized upon by some, thankfully very few, who regard it as a justification - even an advocacy - of racism and xenophobia. He is upset by this and says it is almost always because such people have not read any of his work and are responding to some garbled account of it. He says steelily: "It is an extraordinary misrepresentation to suggest that because I am saying that out there in the natural world things are like X, that that is an advocacy of X. It is almost like saying that because animals do not wear clothes that is an advocacy of nudism. Clearly we can decide to wear clothes, we can clearly decide to use contraception - selfish genes are not going to like the idea of that! Almost everything we do is counter to what selfish genes would prescribe if they could have their way. It is certainly not an advocacy of racism. An explanation of racism perhaps, but then you might as well say that a doctor who explains cancer is advocating cancer."

Richard Dawkins was born in Nairobi, Kenya in 1941. He moved to England at the age of eight when his father, an official in the colonial agricultural civil service in Nyasaland, now Malawi, inherited a farm just outside Oxford. A white colonial upbringing in Africa was followed by boarding schools in England. He first encountered Darwin's work at the age of 16 and was initially sceptical of it: "I did not really believe that it was big enough to do the job of explaining everything. It took a while to realise that it was. It was understanding Darwin that finally destroyed my belief in God."

He managed to scrape into Oxford to read zoology and, a doctorate later, was at Berkeley, California, where he took his first job as an assistant professor. A couple of years later, he was back at Oxford, a location that he does not think he will stray from largely because of his ten-year-old daughter from a previous marriage. In any case, he finds the intellectual atmosphere in Oxford "immensely stimulating" and describes the Oxford zoology department as one of the best in the world.

His parents still live at the farm on which he was brought up and Dawkins says he is like them in many ways: "My father read botany at Oxford and perhaps this has influenced me. My mother has a great love of animals and is passionately concerned about animal welfare - I have certainly been influenced by her in that direction."

Perhaps the one thing that unites Dawkins's critics and supporters is their respect for his writing skills - although those at the receiving end of some of his more aggressive literary missiles might not be so gracious with their praise. He has always read a lot, and long-time favourites include P. G. Wodehouse and Evelyn Waugh. He likes poetry although he does not write any himself and is particularly keen on Yeats, Shakespeare's sonnets and anthologies. His wife, the actress and artist Lalla Ward, reads him sonnets sometimes: "She is a brilliant reader. I can be moved to tears quite easily by her reading. I try to suppress it though because it embarrasses me," he says laughing . Ward has done the illustrations for his new book and is planning to do more for his next, Climbing Mount Improbable, which will be based on the Royal Institution Christmas lectures he gave in 1991.

Dawkins has not carried out any laboratory research for several years now and, while such work still has an allure, he says he is too busy to really miss it. Computer programming has something of the same appeal for him. "On the whole I am happy doing what I am doing. If you do a good piece of research and you publish a very clever paper it is read by people and cited by them but the actual impact you have on most people's minds is not that great - for some of course it is colossal. But I think I have found my level and found what I do best. I like to think that I may inspire other people to do the important work of research and maybe even encourage people to come into science."

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As well as helping to popularise science, he likes to think that his work has helped to influence the way people think both inside and outside biology: "But that may be just putting things in unfamiliar ways, turning them upside down, showing people things that they knew all along but hadn't thought of quite as I describe them. I suppose I play a kind of oblique role in science and I am very happy doing so."