Nature versus nurture

Nature versus nurture
Suresh Menon

The most interesting finding to emerge from the research into the human genome is not the fact that we share a strange kinship with the roundworm or that three-quarters of the genome consists of junk, but that the genetic information all humanity carries is 99.99 per cent identical. The difference between you and Madonna or Tendulkar or Mandela is just 0.01 per cent. In that small figure lies our talent, our beauty, our nature, our ability to run faster or jump higher or solve equations or write poetry or comment about all these things. We survive by the dint of differentiation. The conclusion is not that there is not much difference between a roundworm and us, but that there's not much difference between one man and another. Race never had a scientific basis, despite the manner in which it has been used for narrow political ends. That apartheid in South Africa and Hitler's massacre of Jews were based on a fallacy was known, but not easily accepted. It might be naive, therefore, to expect bigotry and racialprejudice to be wiped out by the `99.99 per cent similarity', but at least it can be said with confidence that there is no scientific basis for bigotry.

The kinship with the roundworm might be fodder for satirists, but it also points to the need for another explanation for our complexity. The roundworm has 959 cells, 302 of which are neurons in its brain. We have 100 trillion cells in our body and over 100 billion brain cells. So, clearly genes do not explain everything. Over the centuries, man's attempts to explain himself (he is the only living creature who finds the need to or has the apparatus to do so) have led him in two different directions. The dilemma is best described by Hume's Fork. The philosopher David Hume put it thus: Either our actions are determined, in which case we are not responsible for them, or they are determined by random events, in which case we are not responsible for them. The genome research, without getting to the philosophical implications of its findings so far (once it is complete, we can no longer avoid the question) seems headed in the direction of compromise. Scientists now believe that genetic inheritance contributes lessto behaviour than was thought at one time; environmental factors count for more. This is the nature versus nurture argument presented more realistically. Neither determines behaviour on its own -- the two interact. To the layman, that might seem obvious, but science tends to work on the exclusion principle, it has to be either/or. As the scientists grapple with the scientific questions, we must prepare answers for the moral, ethical, business, social and political questions that arise out of their work.

Fewer genes means that drugs based on the research could hit the market earlier. An article in Nature magazine has pointed out that currently all drugs are based on just 483 biological targets in the body. That is only a small fraction of the hundreds of thousands in existence. Genes for asthma and Alzheimer's have been identified, and treatment will follow. On the other side of the coin is the `gene hypochondriac' whose life is made hell in anticipation of the illnesses his gene sequence predicts. It might be difficult to convince such a person that by knowing the nature of his future illness, it is possible to find a cure for it.

As our lifespan increases, there will be social changes. There will be a greater percentage of older, healthier men and women who will play a bigger role in the way we live and think. They will have many of the advantages of youth, including fitness, without its disadvantages like inexperience. Poets have been telling us for years that youth is wasted on the young. D-Day, when the entire gene sequence is charted is not far off. Soon, to adapt Wordsworth, Bliss will it be in that dawn to be alive/ But to be old will be very Heaven.

The commercial questions will haunt the law-makers. Soon after the two front-runners in genome research, Celera Genomics and the Human Genome Project, announced their preliminary findings last June, other companies got into the act, offering their data bases for a price. Thus, Incyte Genomics promised access to 120,000 human genes, and DoubleTwist to about 65,000 to 105,000. Their credibility is well below their commercial savvy now since it has become clear that there are less than 40,000 human genes. In fact, as research proceeds, credibility will be a problem, since it is clear that there is a race of sorts to the finish line.

While Celera Genomics is a private company, the Human Genome Project is funded publicly and it is easy to see this as a fight between crass commercialism on the one hand and noble human pursuit on the other. However one views it, there is a race on, and at the end of it is a Nobel Prize. Those who still believe that scientists are above all such human weaknesses need only read James Watson's excellent book, The Double Helix. Francis Crick boasted 48 Februaries ago, ``We've discovered the secret of life,''when he and Watson discovered the structure of the DNA, the double helix. Watson's account of the story has strong elements of personal jealousy and the race-to-the-finish psychology which made him unpopular for a while with his colleagues. The biggest moral question, post-genome, will be the extent to which we can manipulate man. Gene therapy has already raised uncomfortable questions. Is it right to destroy an embryo even if by doing so it is possible to cure Parkinson's disease, for example? Does a pregnant woman have the right to decide on having the baby, her decision being based only on what it might become? James Watson has earned notoriety in recent years by suggesting that a woman can decide to abort the child if he is likely to become a homosexual, for example. But research by Judith Rich Harris has shown that children often have a non-genetic effect on parents than the other way around. Conventional wisdom is that distant fathers and overprotective mothers make sons homosexual. But, Harris haspointed out, the reverse is more likely. Understanding that the son has no masculine concerns, the father withdraws, and the mother overcompensates. The distinction between cause and effect isn't as clear as it is made out to be.

As the research into the genome progresses, questions, if not answers will become clearer. It is tempting to think that simple answers to complex questions will be contained in one of the gene sequences. But somehow it is reassuring to know that such a thing is not possible, that our `humanness' does not reveal itself so easily in the laboratory.