Why I believe parents are morally obliged to genetically modify their children

The decision to allow couples to test their embryos for an inherited bowel cancer gene brings us a step closer to the creation of designer humans.

Parents can now influence the genetic hand their children were once randomly dealt, selecting those with less chance of becoming sick. But some fear this is a slippery slope to a Gattaca -type society, where children are selected for their intelligence, beauty and talent.

As products of evolution, we humans have always chosen our mates instinctively on the basis of genetic fitness - the ability to survive and reproduce healthy offspring, as betrayed through signs such as beauty or smell. With the tools of genetics, offspring can now be selected more reliably.

Embryos can be tested for genetic disorders, from hereditary cancer to dental abnormalities. Athletes can be screened for the fitness-enhancing ACE gene to identify potential Olympic contenders. Gene therapy has been used to turn lazy monkeys into workaholics and polygamous voles into devoted mates by altering the reward centre in the brain. If these results are relevant to humans, it may be possible to genetically modify our personality and cognitive abilities.

A host of possibilities is raised by advances in behavioural genetics that are beginning to reveal the genetic bases of traits such as aggression, alcoholism, anxiety, maternal instinct and homosexuality.

Should we decide what breed of humans to create? Some people believe that children are a gift, of God or Nature, and that we should not interfere in human nature.

Most people, however, implicitly reject this view. We already routinely screen embryos and foetuses for disorders such as Down's syndrome. This modern eugenics is acceptable because it is voluntary - parents are given a choice over what kind of child to have and the aim is to promote the greatest opportunity for a good life.

Last century's eugenics movement, which reached its inglorious climax when the Nazis moved beyond sterilisation to exterminate the "genetically unfit", was especially objectionable because of the coercive imposition of a state vision for a healthy population. The critical question is not whether we should select or enhance our children by altering some gene related to complex behaviour. Rather, we should ask which gene is better for the individual.

It may be difficult to determine whether it is advantageous to have a tendency to be lazy or hard-working, to be monogamous or polygamous. But there will be cases where some genetic intervention is plausibly in a person's interests: enhancing their memory or promoting greater empathy with other people, for instance. Such capabilities are good no matter what one wants to do in life.

One quality in particular is associated with socioeconomic success and staying out of prison: impulse control. A hot temper can destroy a life. If it is possible to genetically correct poor impulse control, we should do so.

Whether we like it or not, our future is now in our hands. But if we do not exercise control over the genetic nature of our offspring, we consign them to the natural lottery and must take responsibility for its consequences.

As parents, we should have children who have a good opportunity of the best life. Rather than fearing genetics, we should embrace it. Genetic selection is not cheating - it is one way to be a responsible and caring parent.

Where an enhancement is clearly good for an individual, we should offer it and let the individual decide. And in the case of the next generation we should let parents decide. To prevent them from making these choices is to consign those who come after us to the ball and chain of our squeamishness and irrationality. We can do better than chance.