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for that’, to spell out the entire sequence of coloured discs strung along the Double Helix and thus reveal the full complement of genes, known as The Genome. There was every reason to suppose that deciphering the full set of genetic instructions of what makes a bacterium a bacterium, a worm a worm, and a common housefly a common housefly would reveal how they are made and how they come to be so readily distinguishable from each other – why the worm should burrow and the fly should fly. Then, at the close of the 1980s, the co-discoverer of the Double Helix, James Watson, proposed what would become the single most ambitious and costly project ever conceived in the history of biology – to spell out the full complement of human genes. Thus the Human Genome Project (HGP) was born, with its promise to make clear what it is in our genes that makes us, ‘us’. The truism that ‘the answer lies in the genes’ is not merely an abstract idea, rather the set of instructions passed down from generation to generation influences every aspect of our being: our physical characteristics, personality, intelligence, predisposition to alcoholism or heart disease, and much else besides. Spell out the human genome in its entirety, and all these phenomena, and more, should finally be accounted for.

      ‘The search for this “Holy Grail” of who we are,’ observed Harvard University’s Walter Gilbert, ‘has now reached its culminating phase, the ultimate goal is the acquisition of all the details of our genome … that will transform our capacity to predict what we will become.’ There could be no greater aspiration than to ‘permit a living creature’, as Robert Sinsheimer, Chancellor of the University of California, put it, ‘for the first time in all time, to understand its origins and design its future’. The Genome Project would, claimed Professor John Savile of Nottingham’s University Hospital, ‘like a mechanical army, systematically destroy ignorance’, while ‘promising unprecedented opportunities for science and medicine’.

      The Human Genome Project was formally launched in 1991, with a projected cost of $3 billion over the fifteen years it was expected it would run. The task of assembling the vast quantity of data generated by spelling out the human genome was divided across several centres, most of them in the United States, Britain and Japan. The scene within those ‘genomes centres’ could have come from a science fiction film – gleaming automated machines as far as the eye could see, labelling each chemical of the Double Helix with its own fluorescent dye which was then ‘excited’ by a laser and the results fed directly into a computer. ‘The Future is Now’ trumpeted the cover of Time magazine, imposing that iconic image of the Double Helix over the shadowy outline of a human figure in the background.

       The Brain

      Meanwhile, the human brain too was about to reveal its secrets. Its physical appearance is quite as familiar as the Double Helix. But the specialisation of those separate parts for seeing, hearing, movement and so on is in a sense deceptive, concealing the crucial question of how their electrical firing translates the sights and sounds of the external world, or summons those evocative childhood memories from the distant past. How does this mere three pounds of soft grey matter within the skull contain the experience of a lifetime?

      Here again, a series of technical innovations, paralleling those of the New Genetics, would permit scientists for the first time to scrutinise the brain ‘in action’. In 1973 the British physicist Godfrey Hounsfield invented the Computed Tomography (CT) scanner, revealing the brain’s internal structure with an almost haunting clarity, revolutionising the diagnosis of strokes and tumours and other forms of mischief. Soon after, the further technical development of Positron Emission Tomography (PET) scanning would transform the CT scanner’s static images or ‘snapshots’ of the brain into ‘moving pictures’.

      Put simply, this is how it works. All of life requires oxygen to drive the chemical reactions in its cells. This oxygen is extracted from the air, inspired in the lungs and transported by blood cells to the tissues. When, for example, we start talking, the firing of the neurons in the language centre of the brain massively increases their demand for oxygen, which can only be met by increasing the bloodflow to that area. The PET scanner detects that increase in bloodflow, converting it into multi-coloured images that pick out the ‘hotspots’ of activity. Now, for the first time, the internal workings of the brain induced by smelling a rose or listening to a violin sonata could be observed as they happened. Or (as here) picking out rhyming words:

      A woman sits quietly waiting for the experiment to begin – her head ensconced in a donut-shaped device, a PET scanning camera. Thirty-one rings of radiation detectors make up the donut, which will scan thirty-one images simultaneously in parallel horizontal lines. She is next injected with a radioactive isotope [of oxygen] and begins to perform the task … The words are presented one above the other on a television monitor. If they rhyme, she taps a response key. Radiation counters estimate how hard the brain region is working … and are transformed into images where higher counts are represented by brighter colours [thus] this colour map of her brain reveals all the regions acting while she is judging the paired words.

      The details will come later, but the PET scanner would create the discipline of modern neuroscience, attracting thousands of young scientists keen to investigate this previously unexplored territory. Recognising the possibilities of the new techniques, the United States Congress in 1989 designated the next ten years as ‘the Decade of the Brain’ in anticipation of the many important new discoveries that would deliver ‘precise and effective means of predicting, modifying and controlling individual behaviour’. ‘The question is not whether the neural machinery [of the brain] will be understood,’ observed Professor of Neurology Antonio Damasio, writing in the journal Scientific American, ‘but when.’

      Throughout the 1990s, both the Human Genome Project and the Decade of the Brain would generate an enormous sense of optimism, rounding off the already prodigious scientific achievements of the previous fifty years. And sure enough, the completion of both projects on the cusp of the new millennium would prove momentous events.

      The completion of the first draft of the Human Genome Project in June 2000 was considered sufficiently important to warrant a press conference in the presidential office of the White House. ‘Nearly two centuries ago in this room, on this floor, Thomas Jefferson spread out a magnificent map … the product of a courageous expedition across the American frontier all the way to the Pacific,’ President Bill Clinton declared. ‘But today the world is joining us here to behold a map of even greater significance. We are here to celebrate the completion of the first survey of the entire human genome. Without a doubt this is the most important, most wondrous map ever produced by mankind.’

      The following year, in February 2001, the two most prestigious science journals, Nature and Science, each published a complete version of that ‘most wondrous map ever produced by mankind’ as a large, multi-coloured poster displaying the full complement of (as it would turn out) twenty-five thousand human genes. It was, as Science observed, ‘an awe-inspiring sight’. Indeed, it was awesome twice over. Back in the 1950s, when Francis Crick and James Watson were working out the structure of the Double Helix, they had no detailed knowledge of a single gene, what it is or what it does. Now, thanks to the techniques of the New Genetics, those involved in the Genome Project had, in less than a decade, successfully culled from those three billion ‘coloured discs’ strung out along its intertwining strands the hard currency of each of the twenty-six thousand genes that determine who we are.

      The Human Genome map, like Thomas Jefferson’s map of the United States, portrays the major features of that genetic landscape with astonishing precision. While it had taken the best part of seven years to find the defective gene responsible for the lung disorder cystic fibrosis, now anyone could locate it from that multi-coloured poster in as many seconds. Here too at a glance you can pick out the gene for the hormone insulin, which controls the level of sugar in the blood, or the haemoglobin molecule that transports oxygen to the tissues. To be

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