The genetic illusion

WHAT is man? Philosophers have debated this question for millennia, reaching no very serious conclusion. Lately, however, philosophy has become rather less fashionable than genetics, which is in the throes of a hugely expensive effort, known as the Human Genome Project, to answer the same question. This project is already showing great promise. It should produce many medical benefits. But it will also throw up some ethical dilemmas. Should humans be genetically engineered; should insurers have access to customers' genetic make-up to assess their risk of disease? And, in the longer run, it is in danger of creating a philosophical misconception of its own: that men's actions are determined by their genes, not by their own free will.
It is not the geneticists who are at fault. The trouble is that other people often read too much into what geneticists do. When a geneticist asks what man is, one obvious answer is: "99% a chimpanzee". This is the percentage by which a person's DNA appears to match that of his nearest non-human relation. What it is to be human is, in that sense, crowded into 1% of the 3 billion genetic "letters" that go to make up a person's genetic material--the human genome.
Reading those 3 billion letters is the task of the genome project, which expects to list all of them within the next few years in the hope of producing new forms of medical diagnosis and treatment (see page). But this is not merely a matter of working out what the genes are. Biologists also need to interpret the messages genes carry, and how those messages interact to build a person. If and when the interpretation is completed, humanity will know its biological self better than was conceivable as little as two decades ago.

After such knowledge
Yet anticipating that interpretation risks recapitulating mistakes that have dogged genetics since its inception. The subject got off to a bad start when the work of its founding genius, Gregor Mendel, was ignored for almost 40 years. The period of this ignorance--the last decades of the 19th century--was marked by the growth of eugenics. This movement proposed to improve humanity by a process tantamount to selective breeding. One strand of it, however, begat America's sterilisation and selective immigration laws of the 1920s, and ultimately led to the Nazi death camps.
     Another strand--concerned with the measurement of human intelligence--rapidly degenerated into a vacuous debate between those who thought intelligence to be largely inherited and those who believed it to be a product of a child's early environment: nature versus nurture, as the argument came to be known. By the time real scientific genetics started its careful, limited experiments on plants and fruit flies and fungi, ideological camps were already established, and prepared to pounce on any result that supported their point of view. Conversely, geneticists with particular points of view were not above making up results to support their own ideologies.
     There is a real danger that this could happen again. The reaction against genetic explanations that followed the excesses of eugenics has lost much of its steam. There seems to be particular public interest in scientific results that purport to show that this or that aspect of human behaviour is under biological control. There is, it is said, a gene for "thrill seeking". Male homosexuality, one result suggests, is inherited down the maternal line. The brains of homosexuals are different from those of heterosexuals. The brains of dyslexics are different from those of people who can read easily. Few of these results have emerged from the genome project itself. But, as time goes by, some such information undoubtedly will, and will strengthen the idea that people's will is not as free as western philosophers have liked to suppose. Or, as it is often put, that biology is destiny.
     Yet this would be an error. Clear limits exist to normal human behaviour, and such limits are obviously genetic. People do not, for instance, eat grass and moo. They do not, except in novels by Edgar Rice Burroughs, swing through the trees. But it is nevertheless true that they could choose to do these things if they wanted to, at least for a time.
     The respectable scientific case against free will is a physicist's case--that every outcome is an inevitable consequence of the arrangement of matter that immediately preceded it. This is not, however, a biologist's case. And it is certainly not a geneticist's case. For "biology is destiny" carries a second, unspoken, premise: "genetics is biology". The conclusion that follows is: "therefore genetics is destiny". Sometimes it is. Men with a fault in the appropriate gene will be colourblind without exception. Usually, though, things are more complex. Height is certainly under genetic control, but genes do not explain why young Japanese are taller than their fathers. The cause is a change of diet. And nutrition is just as "biological" as genetics.
     About a dozen genes are reckoned to control height. Brains are built and regulated by thousands of them. And in addition to this the scope for environmental effects on brain development, and therefore on behaviour and intelligence, is both enormous and commonplace. It is known as learning.
     The complexity of the way the brain develops and functions, and the interaction between genes and environment that is responsible for it, will certainly be illuminated by the genome project. Genes will emerge that, if present in one form rather than another, or present in particular combinations, predispose people to behave one way rather than another. Other genes will cause only those predispositions appropriate to a particular environment to develop. All such predispositions will be expressed in the same way--in the actual wiring of the nerve cells that make up the brain.
     Does this make people prisoners of the way their brain is wired? This question is best addressed by asking not whether it seems difficult for someone to make a particular choice, but whether it seems impossible. Sometimes it clearly is. Certain diseases genuinely rob people of choice. Accidental brain damage can have the same effect. If neurobiology ultimately comes to show that the way someone's brain is wired really does limit their scope for choice in a given situation to no choice at all, then so be it. But even when the genome project is completed, the science that could come to that conclusion will still be a long way off--and just how far off can be imagined by thinking how much a person differs from a chimpanzee, yet how similar is their DNA. So much complexity from so little difference. Genetics has suffered before from a mountain of speculation being built on a molehill of knowledge, and humanity has suffered as a result. For now there is no reason to abandon the belief that people control their own actions--and should be held responsible for them.