Sack the shrink, your dreams are simply scrambled brain-stem impulses. Edward O. Wilson, best known for his love of ants, tells Tim Cornwell about his latest bugbear

Ants appear to Edward O. Wilson in dreams. The Harvard myrmecologist, who in his lifetime has discovered hundreds of new species of ant, and spent much of his working life as curator to the "world's best" ant collection, dreams of them "all the time". But he is not nipped by giant insects, nor pinned down and bottled up in some nightmare borrowed from H. G. Wells or Roald Dahl. These are a naturalist's dreams, of a biologist driven by a lifelong compulsion to collect and observe.

"Two elements go into it," says Wilson, 69. "One is that I am on an expedition, collecting, and I get a certain amount of pleasure out of that, hunting, finding ants, usually in a faraway place, where there are new species and so on.

"The other aspect of my dreams is the anxiety part where I'm having a very hard time getting to the rainforest, which is where all entomologists go in the tropics if they want a lot of different kinds of bugs. In my anxiety dreams, I realise I have not been able to get to this rainforest, usually on an island, I go hunting for it in the dream and I can't find it. It looks like a rainforest on the horizon, and I can't get to it. When I get there it turns out to be a hedgerow with a field beyond it ... I dream of being in a place and looking, and it's too late, too late, I've got to go."

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Snakes also appear in Wilson's dreams, but not writhing at the bottom of his bed. He's usually trying to catch one or understand one. As with ants, Wilson has largely overcome the usual reptile phobias, having been a snake-handler since Southern boyhood (though he is an arachnophobe). But once in a while the dream-snake turns into a mythic serpent, huge and high and menacing "and I'm having difficulty managing it".

But do these dreams mean anything? Or the other, more familiar ones, where Wilson is on his way to a lecture, and "I don't know how to get there and I'm not sure what I'm going to talk about"? Sigmund Freud, Amazonian shamans, the Bible, and LSD prophet Timothy Leary have all treated dreams as laden with meaning. Superstition and old wives' tales, Wilson argues in his latest book, Consilience: The Unity of Knowledge. Dogs dream and so do we.

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"Natural sleep and drug-induced dreams have long been viewed in western civilisation as a portal to the divine," Wilson writes. Not in Wilson's book, however. Dreams, for him, are nothing more than impulses originating in the brain stem at a time when our bodies are temporarily paralysed.

Lacking input from the senses, the brain scrambles, producing a "kind of insanity, a rush of visions, largely unconnected to reality", in what is probably a side-effect of the reorganisation of the memory banks. The real dreaming, he cleverly concludes, takes place when we wake up, review the lingering images and try to impose meaning. As a result, "dream interpretation itself becomes a kind of fantasy ... psychoanalytic theories relating to dreaming, as well as parallel supernatural interpretations arising in myth and religion, are at one and the same time emotionally convincing and factually incorrect".

All of which is part of Wilson's argument that even the most prominent psychotherapist is reduced to quackery unless he draws input from neurological research and behavioural genetics, borrowing from the fundamental laws of other disciplines to shed essential insight on his own. The psychotherapist should consider that dreams possibly have a Darwinian function: that when we dream, we deepen moods and improve chances of both survival and sexual responses. Sure, bear Freud in mind - "because dreams are not entirely random" - but make sure you know your neurobiology too.

The new book from the two-time Pulitzer Prize winner, published in the United Kingdom next month, comes with a lofty title and a high-minded appeal for the "great branches of learning" - the natural and social sciences - to find their common ground. It is a plea for the art historian to lie down with the molecular geneticist. Consilience, with its throwback to the optimism of the Enlightenment, offers the "key to unification", the "jumping together" of knowledge by the linking of fundamental facts and theories across disciplines It even offers a peaceful resolution to the nature-nurture debate.

Sometimes Consilience reads like an approach to some greater scientific God, a "grail of objective truth"; at others, like the academic's answer to corporate synergy. Slightly disingenuously, it is also a vehicle for flogging Wilson's well-known ideas on sociobiology and their enhanced 1990s model, evolutionary psychology. But it may also mark a closing of a circle in the life of a biologist whose first and last love is foraging for fauna but whose observations on human societies elevated him to the status of public intellectual. The man who built his career studying the tiniest creatures invites us to examine the atom to find the answers to dreams - and to religion, sex, art, and how to save the earth.

Wilson stresses the importance of ants to the ecosystem - in the Amazon, they have four times the biomass of all the large vertebrates put together. He is now attempting to wrap up a massive monograph on the western hemispheric species of the ant genus Pheidole, a task he compares to the "Mount Everest of ant classification". At the last count he had 636 species, of which 346 are "new to science".

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His other great passion is the preservation of ecosystems. "We are the greatest destroyer of life since the ten-kilometre wide meteorite that landed near Yucatan and ended the age of reptiles 65 million years ago." Those who assume we can fix the planet as we fouled it up have no grasp of what it takes to keep an ecosystem ticking.

It seems something of a dilemma for Wilson that while he and and others offer genetic explanations for all kinds of behaviours, they struggle to find an instinct for conservation. Primitive man was presumably more interested in subjugating nature than preserving it. But what accounts for the "psychic crippling" that he says occurs when we are deprived of a natural environment, why do patients recover faster in a room with a view?

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"The difficulty is that there has been almost no development of a field of environmental psychology," Wilson says. "This is astonishing. There has been no systematic attempt to break apart what are our responses to the environment and our innate needs."

Wilson came to biology armed with a passion for fieldwork, and, as he readily admits, a weakness in maths. But in his late twenties, his Harvard career just under way, the field was turned upside down by the molecular biologists, whose arrival is described almost in the terms of an Anschluss by scientific bully boys. He describes James Dewey Watson, co-discoverer of the structure of DNA, as "the most unpleasant human being I had ever met", a man who scorned traditional biology of Wilson's kind as "infested by stamp collectors who lacked the wit to transform their subject into a modern science".

Forty years on, under the banner of Consilience, Wilson is frankly telling social scientists that they need to get their house in order. Neurobiologists, virologists and molecular geneticists understand and encourage one another even as they compete, he writes. But for the most part anthropologists, economists, sociologists and political scientists fail to agree. They are still suffering as a result of Marx's and Freud's refusal to accept the scientific facts, and they need Consilience. "They are intellectually capable ... their leading thinkers will tell you, if asked, that all is well, that the disciplines are on track - sort of, more or less. Still, it is obvious to even casual inspection that the efforts of social scientists are snarled by disunity and a failure of vision."

But the science to which they are supposed to pin their colours, it turns out, is the science of the mind, "supremely important to the consilience programme". The mind is shaped by the "hereditary epigenetic rules of human nature", epigenetic rules being "innate operations in the sensory system and brain", a brain developed by Darwinian evolution for survival.

Social scientists missed the collapse of communist rule in the Soviet Union, for example, because they overlooked the behavioural trend of ethnic hostility. Evolutionary psychology, apparently, could have put them straight. Students of religion, meanwhile, must realise that worship of an authority figure is clearly an instinctive behaviour for the species Homo sapiens, a ritual obeisance that mirrors the submissive behaviour of an Alpha male among wolves or rhesus monkeys.

In 1978 Wilson was doused with a jug of iced water at an academic conference for saying this sort of stuff, with sociobiology denounced for guilt by association with sexism, racism and eugenics. Now the notion has found a broad acceptance. In Consilience, he offers a peace pipe to critics by writing in a role for culture - of the kind that militates against rape or incest - in what he calls "gene-cultural evolution". Culture and breeding are intertwined, it appears, as the invisible hand has promoted genes that get along with the existing cultural rules.

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Wilson is most eloquent in Consilience in its last chapter. In it he surmises that, thanks to the mapping of genes, humanity will replace evolution with genetic choice and be "positioned God-like to take control of its ultimate fate". This "volitional evolution", as he calls it, will "present the most profound intellectual and ethical choices humanity has ever faced ... Homo sapiens, the first truly free species, is about to decommission natural selection, the force that made us."