The study, by medical scientists and researchers at the University of Plymouth, is said to be the first of its kind and will involve gene- typing and long-term observation of 50,000 babies born in Devon and Cornwall over the next three years.
Part of the investigation has involved mapping the genes of Cornish farmers and fishermen, using blood samples and family trees going back three generations. But the research has generated an unexpectedly fierce reaction from members of the public and has revealed a public sensitivity to genetic research that has caught the researchers unawares.
The research, like all genetics, touches upon personal and family matters - which raises sensitive issues of individual privacy - but also strays into the minefields of nationalism, race and ethnic origin. Cornish patriots, including Dr Philip Payton, director of Exeter University's Institute of Cornish Studies, believe this kind of work is a short but dangerous step down the road to a kind of biological apartheid.
Paul Holmes, a Cornwall county councillor and Liberal candidate in the European parliamentary elections, goes further. 'Trying to find out whether a disease comes from a certain race is very disturbing indeed,' he says. 'Where does it all end?'
The Plymouth team is not the first academic study group to end up with tingling feet after treading in the minefield of Cornish politics. Three years ago at a British Association meeting in Plymouth, Dr Malcolm Smith, lecturer in anthropology at Durham University, raised doubts about the strength of Cornish genetic links with other Celtic groups in Britain. Media headlines trumpeted, 'The Cornish are no more Celtic than your average Brummie' - and the Cornish were furious.
The Plymouth scientists' problems stem, in part, from the way in which the university announced the study, saying that gene maps of Cornish adults were being prepared 'which might distinguish a person of true Cornish (or Celtic) origins from an English person'.
Dr Andy Demaine, senior lecturer in medicine, was quoted as saying: 'Using molecular genetic techniques, it is now possible to investigate the ancestral origins of different populations. This type of study is of particular importance because often it can shed new light on why certain individuals develop a disease while others do not.'
Dr Payton, who specialises in ethnic identity, says sharply: 'I tend to get a bit academically hot under the collar about some of these spurious generalisations. If there is some medical reason for identifying a propensity towards childhood diseases in certain parts of the population, that's useful; but the wider insinuation, that this tells us something about Cornish ethnic identity, is dangerously wrong.
'It is typical of the kind of Victorian pseudo-science in the 19th century when there was this great interest in the races of Britain. People went around measuring people's heads and came up with ideas that there was a classical East Anglian type, who was tall and fair, compared with the Cornishman who was stocky and dark. What they were doing was picking one or two people who filled their prejudiced picture and describing them as the norm.'
Dr Payton, whose recent book Cornwall Since The War plots the racial minefield of attempts to identify Cornish ethnicity, adds: 'People can quite easily be persuaded that genetic make-up has an ethnic identity. That is a very dangerous equation to make because ethnic identity is quite distinct from genetic make-up.'
Some inherited diseases do tend to occur disproportionately often in some ethic groups compared with others. Cystic fibrosis, for example, is the commonest genetic disease in northern European populations, whereas sickle cell disease occurs predominantly among people of Afro-Caribbean descent.
Paul Holmes, a former member of the Cornish nationalist movement Mebyon Kernow and one of 2,500 Cornish speakers in the county, believes attempts to identify 'pure' Cornish people are flawed due to years of immigration by English and other settlers.
'You would have a hell of a job finding a 100 per cent Cornishman these days,' he says. 'If all Cornish people did their family trees, it wouldn't take them long to find some English blood somewhere.
'The fact is, being Cornish is a way of thinking, a passion for all things Cornish. Cornishness is a state of mind, not a state of genes.'
The Plymouth team's work is passionately defended by one of its members, Dr Ann Millward, senior clinical lecturer. 'We've been very aware of the sensitivities of the Cornish, that people might be very suspicious of us,' she says. 'In fact, the response from people there has been tremendous. We accept that it is becoming increasingly difficult, in our innocent search for diabetes genes, to find a population that is purely Cornish. But if you're taking people who've lived in the same village and married there for generations, the genes you find in those communities will be less adulterated than those in any other place in the British Isles.
'Speaking as a Welsh Celt, I'd be the first to agree that culture is what holds Cornishness together. And, of course, the reality is that genetics forms only a tiny bit of that culture. I think the two sciences of medicine and sociology are complementary and that we ought to learn from each other.'
Dr Millward concluded: 'What one must not forget here is that we are trying to understand why young children in the last two decades are twice as likely to get diabetes and develop renal failure, blindness and risk the loss of limbs. Anyone with a heart would want to help with this sort of research. Trying to hide information that may be available from different types of population is much more sinister.
'Our motives here are entirely open: to understand the genetics that trigger diabetes in susceptible children. Protection and prevention are better than any treatment. I think it cannot be seen in any other context.'
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