CHAIN 26
LENGTH 3 REPETITION 0.0 SCORE 0.0
fault 1 misconception 1 illusion 1
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 .