Flaps over patenting biological material, especially DNA, are not new, but they are growing louder as science reaches out across the human family tree to pluck at exotic genes that could form the basis of new and expensive drugs.

The thrust of such "diversity research" has gathered momentum only in the last decade as experts began unraveling the biological mysteries of race and ethnicity. Along the way, they have discovered that different human populations have evolved unique resistances or susceptibilities to common diseases.

The key lies hidden within the 3 billion nucleotides of DNA within each of our cells that code for who we are, what we look like and how we function.

Click for chart of various locations of disease-causing genes on chromosomes.

Though the similarity in all ethnic groups' DNA is boggling--all our blueprints differ on average by just one nucleotide in every 10,000--enough minute differences can accumulate over the generations to impart subtle advantages in warding off infections and illnesses. In effect, natural selection has thousands of such complex experiments running in diverse human populations all the time.

"We basically let Mother Nature do our work for us," said Georgia Dunston, a Howard University geneticist who has helped plan the gene survey proposed by the diversity project. "Why waste years of research trying to come up with cures from scratch? Evolution tells us that there are groups out there whose genes have been tinkering with ways to fight disease since day one."

How do beneficial genes settle out in different ethnic groups?

Scientists credit three elusive forces of evolution: time, isolation and group size.

It is difficult for unique traits to gain a foothold within large, dynamic populations, geneticists say, because they can be easily swamped or diluted by the constant influx and outflow of genes, the swirling of genetic tides.

Only in smaller, more stable populations--especially ones where oceans, deserts or mountains minimize outmarriage--can the subtlest genetic ticks become accentuated and magnified. In these cases, a positive mutation, such as one that imparts a tougher immune response, can percolate widely through the gene pool within a few thousand years.

The sort of biological solitude required for such differentiation, experts note, is increasingly rare in today's cosmopolitan world.

"You can't really go gene hunting in Chicago," said Alan Shuldiner, a geneticist at the University of Maryland who recently uncovered genes associated with obesity in Native American tribes. "There's so much intermixing and so much environmental variability that the job would be a nightmare. That's why remote populations make perfect laboratories."

One human experiment that has become legendary among geneticists is the village of Limone Sul Garda in Italy.

The medieval village, perched on a lake, was untouched by Italy's road system until the 1950s. Its gene pool remained largely unrippled by outside gene flow until that time. Researchers have discovered to their amazement that the residents, though they eat the same rich foods as neighbors, suffer almost no heart disease.

Geneticists have now isolated a peculiar mutation--thought to have first appeared randomly in a resident in the 1700s--in the villagers' DNA called the A-1 Milano gene, a localized oddity that appears to gird them against the ravages of atherosclerosis, or hardening of the arteries--one of the most common diseases in the industrialized world.

"You can imagine the sort of therapeutic potential discoveries like these have," said Robert Farrell, a professor of human genetics at the University of Pittsburgh who is studying diabetes and hypertension in different population groups. "That town has been combed by dozens of researchers looking for ways to translate whatever that gene does into some sort of synthetic drug. The payback would be amazing."

Yet it isn't just unique resistances to illness that diversity researchers are homing in on. Tight-knit human groups that suffer unusually high rates of inherited ailments also have caught the eye of gene hunters because they set the stage for mapping and understanding the workings of complex disease genes.

The granddaddy of all such population-specific disease studies involves the Pima Indians of Arizona and late-onset diabetes.

A desert people whose genes have adapted over the centuries to a lean, hunter-gatherer existence, the Pimas have been riddled by health problems associated with the switch to processed foods and a more sedentary lifestyle. The 6,000-member tribe suffers the highest diabetes rate of any ethnic group in the world. For 30 years, researchers at the NIH have been tracing Pimas' genealogies and drawing their blood, trying to crack the genetic underpinnings of a disease that afflicts millions worldwide.

"We'd really like to see some breakthroughs," said Viella Johnson, director of the hospital in Sacaton, the Pimas' tribal headquarters an hour drive east of Phoenix. "We've got families where half the people in them are diabetes patients. It's a plague."

In the brave new world of diversity research, places such as Sacaton--with its adobe huts melting into the Sonoran Desert and its dogs curled on a lonely main street--are becoming the unlikely new capitals of disease research.

So are the battered trailers and tents of Israel's Bedouin, who are being studied for clues to obesity and certain inherited forms of deafness. So are the small towns of Canada's Quebecois, who are the subjects of a quest for the genetic underpinnings of manic depression. And so are the remote villages of the Arhuacan Indians of Colombia's rugged Santa Marta Mountains, who, like the Hagahai, play host to a type of virus associated with leukemia and AIDS.

"The irony of all this is that by focusing our attention on the white European populations that can afford advanced medical care . . . we've been missing the boat on genetic variation for a long time," said Roger Rosenberg, a University of Texas researcher who is studying Oklahoma's Cherokees for their remarkable resistance to Alzheimer's disease, a fatal degeneration of the nervous system. "This is a whole new frontier."

If there were any doubts about the promise of such research, one need only follow the rainbow of human diversity down to the pot of biomedical gold--an economic reality that is triggering the most volatile debates over the commercialization of DNA from small and often poor populations.

Big pharmaceutical companies are quietly sinking millions of dollars into the sort of massive DNA surveying that purely anthropological proposals such as the diversity project have been pushing for years.

The stakes, even at this early stage, are tantalizing:

- Multiple sclerosis researchers supported by Genethon, a French biomedical firm, have discovered a remote population on Reunion Island in the Indian Ocean that seems to be immune from the crippling effects of the illness, even though they carry the disease genes. A "protective" genetic factor might be in play and, if ever isolated, could lead to lucrative new drugs for millions of MS sufferers.

- Asthma experts are testing a hotbed of bronchial disease on Tristan da Cunha island in the South Atlantic, where a third of the roughly 300 interrelated farmers suffer from the ailment. The California firm Sequana Therapies has signed a $70 million deal with Boehringer Ingelheim, a German pharmaceutical company, to help find the Tristanians' disease genes and develop a broad-scale genetic therapy from them. Sequana expects to announce the discovery of its first asthma-related gene as soon as next year, one of the first tangible returns from diversity research.

- In a breathtaking gene hunt that will dwarf the diversity project, the international biomedical company Genset signed a deal last year to sift China's 1.2 billion citizens for mutations that might have beneficial health effects. The company will focus on China's remote rural populations and its 40-plus minority groups. The value of the contract, like that of an unexplored mining lease, is incalculable but likely immense.

Which is why indigenous-rights advocates are crying foul.

"You've got this potentially lucrative traffic in human DNA zipping from lab to lab across the world and none of it benefits the donors," said Edward Hammond, an activist with the Canada-based Rural Advancement Fund International, or RAFI, a group concerned with biodiversity and tribal property rights. "There's just this huge potential for exploitation."