Models assembled from spare parts

Early one morning I heard by chance a radio programme from the Open University. It was about Shakespeare's Tempest. The lecturer compared the shipwreck of Prospero and his family on the Bermouthes with the fate of a starship crew stranded on a remote planet. I was enthralled. Before, The Tempest was no more than a dim memory of required reading for the school certificate. As I listened, what once had failed to ignite my imagination became a delight. Christian de Duve's book, Vital Dust, moved me in the same way.

In the 1950s I spent several years doing biochemistry for the Medical Research Council. It was not my favourite science. I knew a fair amount of it but only to the extent that my mind was a clutter of biochemical facts. Had Vital Dust been there for me to read then, the course of my life might have been different. It is one of those rare books that open and tidy the mind. Though it is too late now for me to think of taking up biochemistry again but this book has had a profound effect.

It has brought biochemistry alive and made me understand what it has been about in the years since the 1950s. Scientists tend to limit their reading to their own subject. I am sure that many of us who are not versed in molecular biology intend one day to take the time to bring our minds in tune with this most important science. Dear colleagues here is your chance. Before this book I had also unwisely turned aside from thinking about the origin of life. I did so because it seemed remote, something as impractical as speculating on whether the universe just happened, or was created. De Duve, a biochemist who won the Nobel prize for medicine, explains in exquisite detail how in fact life most probably assembled itself from a convenient presence of molecular spare parts. His time span starts with the seminal events that took place when physics and chemistry alone described the earth. It goes on through the strange sequence of chemical worlds to our first true ancestor, a living cell informed by DNA. The story continues through to the human world now.

The distinguished cosmologist Fred Hoyle made a rare error when he rejected the possibility that life might have originated on the earth's surface. He thought it impossible for a living cell to evolve from the mix of chemicals coating the surface of the new-formed planet. He held this view strongly and said: such an event is as unlikely as that of a Boeing 747 rising, ready to fly, from a tornado-swept junk yard.

This book is a complete and exhaustive answer to Hoyle's puzzlement. De Duve explains how life began here on earth and reminds us that in the real world neither the aircraft nor the first living cell appeared as a single event. Both were assembled from preformed parts. The universe is no junk yard. It is something that expands and cools with all the confidence of a just exploded bomb. In its early state the heat was intense and the atoms were all homogenised. Molecules assembled as it cooled, both in the depths of space and on small rocky places like the earth. These made the vital dust from which all life has emerged. By a cosmic imperative, the atoms of that key element carbon did not all, or even mostly, join with other atoms in a random way. Remarkably, they often combined to form the spare parts for life's assembly. To be sure there were junk com£ but among them were the components of life.

Imagine a world of game players who had never before seen chess and on which, among other things, chess pieces and boards appeared. It would not be surprising if before long they played chess. So it is with us, the pieces of our game were preassembled before it began. Whether or not the universe was purposefully built, this book confirms that we need not invoke purpose to explain life's assembly from its constituent atoms.

This story of our evolution has both feeling and authority. Here is an example where the author explains how living cells might form from their constituent parts: "This reconstruction phenomenon is one of the most remarkable known instances of the spontaneous assembly of a complex structure. The recipe is astonishingly simple. Take some juice from dividing cells, throw in any old piece of naked DNA - even DNA that has never been near a eukaryotic cell - add a little ATP, and, lo and behold, in a matter of two or three hours a perfectly respectable envelope assembles around the DNA, complete with double membrane, inner lining, and pores. Inside the mininucleus, the DNA even has formed a beaded string coiled into a miniature chromosome. In this process, hundreds of distinct pieces scattered around in the cell extract have come together in a seemingly miraculous fashion, summoned by no more than the added DNA and supplied with energy by the ATP."

To my delight the author said little about dinosaurs. The skeleton of one of these giant reptiles dominates the entrance hall of the Natural History Museum in London. It stands there a disproportionate symbol of the lurid side of natural history. These giant lizards ruled for less than a 20th of the time span of life. I can understand how children thrill at the sight of the monsters but there is more to evolutionary science than a model of a plesiosaur.

De Duve limits his account of dinosaurs to the events that made them extinct 65 million years ago. He supports the discoveries of the Alvarez family, who argued that it was the consequence of a collision between the earth and an asteroid. The story of that devastating event shows us how resilient is life. The quest for the origin of life is a kind of antidetective story. Not who did it, but how did it all come about by chance in a universe where the laws of nature loaded the odds in its favour?

Scientists, like detectives, prefer the tangible evidence of their eyes and their instruments. The views of witnesses are less accurate. Science is so fragmented that we have no option but to trust the words of colleagues in other fields to fill our voids of ignorance. De Duve makes it easy for us to distinguish between the reliable fact drawn from his own work and the secondhand statements of witnesses chosen from other fields of science. Only once did I find this evidence verging on hearsay. This was when he cited geochemists who claimed that the land surface was a barren desert during the first three billion years of life. I find this hard to believe and prefer to think that the abundant unicellular life moved from the oceans to the land soon after life began.

True, only rarely do soft bodied micro-organisms leave fossils but there is other evidence of things happening on the land long ago. Take the strange true story of the natural nuclear reactors of Gabon. These operated two billion years ago. They are an extraordinary anachronism and difficult to explain, apart from the known tendency of some bacteria to gather and concentrate uranium.

As I read on I wished that the author lived nearby and we could talk. I wanted to ask, did he believe in that old half-truth beloved of biologists: life adapts to what it finds? Did those early bacteria, which gestated in the warm womb of precellular life, have to adapt to the cooler world into which they were born? Or, did they also inadvertently make it cool by reversing the greenhouse effect - by using as food the carbon dioxide that kept them warm? Were they like us unintentionally obliged to mess with their environment? Should we be wondering not only about why we are here but also about the effect of our presence? How much have we changed the earth and the universe since we appeared? How will this affect our successors and the world they inhabit?

The biologist, E. O. Wilson, speaking as an observer of the earth from space, regretted the fact that the first intelligent species happened to be a tribal carnivore not some gentle herbivore. De Duve, in the conclusion of his book, echoes these regrets. Like most thoughtful commentators on our state he sees the overgrowth of people and their use of energy as the greatest threat. I agree with him that the specific dangers we pose to the rest of life are the extent to which we usurp their habitats, and change their climate. He wonders if we will evolve into superorganisms and if so, how much we might lose individual freedom. Perhaps our cities are the forerunners of the human nests to come.

De Duve does not dodge anything, and in his closing chapters, he tackles those flimsy concerns that flutter like moths on the grey fabric separating science from philosophy. He gives us his personal thoughts about our place in the universe. He tells us how these stand between the paradigmatic opposites of Teilhard de Chardin, the Jesuit palaeontologist, and Jacques Monod, the existentialist geneticist. This is a comforting and cheering book by a wise and modest man. It made me glad to have spent my life doing science and wondering about the natural world. I must admit that his comments on Gaia were so fair, just and accurate that I feel a special warmth towards him and a prejudice in his favour. Fortunately I came upon them late in the reading and long after the book had won my respect.

James Lovelock is an independent scientist who originated the Gaia hypothesis.