In 1953, a young chemist named Stanley Miller carried out a historic experiment at the University of Chicago. He attempted to recreate the conditions during the Earth's early days by sparking electricity through a mixture of water and gases sealed in a flask. When Miller analysed the results, he was pleased to find traces of amino acids, the building blocks of proteins.
His experiment entered folklore as a pioneering attempt to "make life in a test tube". The success of his simple procedure fostered the belief that it was the first step on a road to life, down which a chemical soup would be conveyed by the passage of time. In other words, by doing more of the same sort of thing, eventually some kind of life would be produced.
To many people, the idea of creating life in the laboratory seems like science fiction. Yet some scientists claim they are on the verge of doing it.
The origin of life remains a tantalising puzzle, shrouded by the mists of time. If scientists could create a second sample of life in the lab, it would yield vital clues about how we got here. Somehow, billions of years ago, a mixture of lifeless chemicals turned themselves into a living cell. Repeating the chemical steps under controlled conditions could yield the first artificial life form.
I see no reason in principle why synthetic life could not be made. However, most scientists working on this challenge are simply barking up the wrong tree. In the 19th century, life was seen as a type of magic matter that emerged from the primordial ooze. The idea grew that this organic matter could be cooked up in the laboratory from a primordial broth if only the right ingredients were identified. It was in this spirit that Miller performed his famous experiment, and more refined versions have been carried out many times since. Disappointingly, researchers remain stuck at the building block stage.
There is a fundamental reason for this impasse. Life, as we now know it, is not magic matter. It isn't something that can be incubated by the methods of 19th-century chemistry. Nor can it be conjured up by infusing matter with energy, such as a bolt of electricity, à la Dr Frankenstein. There is no life force over and above normal intermolecular forces.
Instead, the living cell is best thought of as a supercomputer - an information processing and replicating system of astonishing complexity. DNA is not a special life-giving molecule, but a genetic databank that transmits its information using a mathematical code. Most of the workings of the cell are best described, not in terms of material stuff - hardware - but as information, or software. Trying to make life by mixing chemicals in a test tube is like soldering switches and wires in an attempt to produce Windows 98. It won't work because it addresses the problem at the wrong conceptual level.
The approach pioneered by Miller is bottom-up, synthesising the building blocks of life from inorganic substances and then trying to assemble them into more complex structures. Meanwhile, molecular biologists have been making strides with a top-down approach, breaking apart the innards of bacteria and viruses, and reassembling the components. Just last month, Craig Venter, famous for his pioneering work on the human genome project, announced his intention to create a brand new life form. Venter plans to strip down and reconstruct the genome of Mycoplasma genitalium, a primitive microbe that inhabits the genital tract.
But this isn't making life so much as rearranging it. Even a simple bacterium is a vast assemblage of intricately crafted molecules, many of them elaborately customised. Although those specialised molecules are not themselves living, they are the products of living things. Scientists make use of them in their microbial tinkering. In other words, they use the products of living organisms to re-make living organisms. They remain a long way from being able to put together a living cell from scratch.
If artificial life is manufactured, it will be by applying the lessons of information technology and nanotechnology rather than organic chemistry. These are emerging fields, and the principles that underlie them are only dimly perceived. The hottest topic is quantum computation - an attempt to harness the weird properties of electrons and atoms to process information at the molecular level. Here, the concept of information is transformed, and the rules for processing it are different. Quantum computation enthusiasts foresee a leap in processing power if the technology can be made to work. Perhaps this could pave the way to creating life in the lab.
Which leaves us with a curious conundrum. How did nature fabricate the world's first digital information processor - the original living cell - from the blind chaos of blundering molecules? How did molecular hardware get to write its own software? The answer must wait until we understand the nature of information, and the principles that govern its dynamics and complexity.
· Paul Davies is a visiting professor at Imperial College and author of The Fifth Miracle: the Search for the Origin of Life
pcwd@ozemail.com.au