At the other end of the human spectrum, the news that fertility treatment in Italy has allowed a black woman to give birth to a white child has added to moral unease about biomedical science.
Professor Cohen, director of the renowned Centre d'Etude du Polymorphisme Humain (CEPH) in Paris, who announced the discoveries yesterday, has persuaded the centre to set up the world's first department dedicated to ethics of the new genetics. Due to open in two weeks, it will promote public debates every few weeks.
In an interview with the Independent, Professor Cohen said: 'Every day we find something that raises an ethical problem to which we don't know the answer. I feel that society should decide. Society is asking too much of its scientists. It is asking them to find cures for diseases, the money to do it and to decide how society should react to their work. I say, let's do it
The researchers at CEPH have studied the make-up of 338 French centenarians and found a significant number carried specific variants of two genes that appeared to make them resistant to killer diseases in old age - specifically heart disease and Alzheimer's disease.
Last month the same French laboratory, again led by Professor Cohen, announced that it had produced the first physical 'map' of the entire human genetic blueprint - a breakthrough in the new biological sciences.
But Professor Cohen is concerned that his latest findings, reported in the January issue of Nature Genetics, might prompt 'some stupid insurance companies' to try to test for the genes that influence longevity. 'I must convince them that although our findings are statistically significant for a group, for an individual they would not be a very reliable indicator.'
He did concede, however, that a person carrying the right gene varieties has twice the chance of reaching a grand old age. He also said that it is looking increasingly likely that only a small number of genes are responsible for protecting against a large range of fatal diseases - making it easier to identify people who carry them.
Both the genes the French scientists examined were known to influence the cardiovascular, central nervous and immune systems. What the team has discovered is an unexpected linkage between these genes and human longevity. The genes are named in shorthand 'ApoE' and 'Ace', since they code for substances in the body called Apolipoprotein E and angiotensin- converting enzyme.
The people studied were all over 99 when they gave blood samples, and came from all over France. A significantly lower number than expected shared a variety of the ApoE gene known as E4, and a significantly higher number than expected shared variety of the ApoE gene known as E2.
The low incidence of the E4 variety makes sense, since its presence is associated with heart disease and Alzheimer's. The high incidence of E2 is less easy to understand, since this has been associated with raising the chance of developing heart disease. Even more paradoxical was the finding that a higher number of the group than expected carried a variant of the Ace gene known to predispose people to heart attack.
This suggests that these last two varieties may carry with them some unknown beneficial or protective effect late in life. This would invalidate a simple genetic test by insurance companies since certain genes may be risky and beneficial at different stages of life.
Another problem is that E4 is a risk factor that appears to lower the ability to deal with raised cholesterol levels. It might be helpful to test someone and advise them to watch their diet. But if scientists find someone has genes that make them more likely to develop Alzheimer's, Professor Cohen questions the value of this since there is nothing that can be done about it.Reuse content