In a beat-up refrigerator humming away in his laboratory storeroom, Ken Weiss is storing vials of human blood: the largest gene pool left of a tribe of people inexorably vanishing from the Earth.

The insides of the freezer, not much different from ones used by many people to store groceries, hold the DNA of 12,000 Yanomamo Indians, a fierce Amazonian tribe that lives in Brazil near the watershed of the Orinoco River. The blood samples were collected by anthropologists a generation ago, and there are now more vials in the nondescript room at Pennsylvania State University where Weiss is a researcher than there are Yanomamos still alive.Like many remote populations, the Yanomamo have been ravaged by Western diseases and, in this case, the shotguns of invading gold prospectors. Their rain forest home is scarred by airstrips and mines. Of a population numbering in the tens of thousands at the turn of the century, fewer than 10,000 remain.

So it is that Weiss' storehouse has become one obscure if vivid example of a genetic quest so vast, controversial and unprecedented that even those who know of its existence can't agree on its principal goal.

It is the Human Genome Diversity Project, a title that has proved confusing because it is so close to the more famous Human Genome Project that is mapping the entire code of human DNA.

By contrast, the Human Genome Diversity Project, over five years and at a cost of $25 million, calls on geneticists at universities worldwide to collect 10,000 blood samples from at least 400 ethnic groups ranging from Afghans to Apaches, from Basques to African Bushmen.

In short, it is the first genetic survey of humankind, a painstaking portrait of how and why members of the human species duplicate or differ from one another.

Weiss is the North American coordinator of the project, which is awaiting approval by the National Academy of Sciences, a step that would open it to government funding and increase its public profile. If approved as expected this summer, the project would serve as an official institutional umbrella for research that has been going on unofficially for decades by a scattered group of scientists and commercial researchers.

Which human tissue samples will come under the project's aegis--those of the Yonomamo included--is just one of the complicated ethical and logistical questions that will have to be resolved.

To some, the project is a scramble to salvage the fading biodiversity of our species--a genetic inheritance that shrinks with the demise of every tribe such as the Yanomamo. Moreover, by collecting and comparing the the DNA from the far-flung populations, scientists say they will at last be able to sketch a global family tree and "read" the tale of human evolution, how our ancestors populated the Earth.

Still others call the diversity project a medical bonanza that, by exploring why some groups resist certain diseases, might lead to breakthroughs in the treatments of ailments ranging from Alzheimer's disease to diabetes.

But it is the project's revelations about race that promise to rattle our perceptions of identity the most and ignite debate in classrooms, taverns and homes across the world.

Indeed, the father of the project, Luigi Luca Cavalli-Sforza, an eminent Stanford University professor who has slogged the globe collecting blood samples from Italian villages to sweltering rain forests, has received an incongruous trickle of hate mail:

How dare Cavalli-Sforza suggest, the obscenity-spattered missives read, that our notions of race are irrelevant and that groups such as blacks and whites--or anybody else for that matter--are basically the same.

"Outward appearances tell almost nothing about our roots--the shapes of our noses, the color of our skins change with climate," said Cavalli-Sforza, a reserved, silver-haired academic with an elegant Mediterranean accent, impatiently waving off the racist attacks. "It's our genes that tell our story best."

Meanwhile, a vocal, angry minority see the project as something altogether different: a cultural ripoff, or at least a callous abuse of aboriginal rights.

As the debate escalates, the vast store of human tissue that Cavalli-Sforza and others have collected will be carefully cultured in labs so that the cells live on for decades--a biotech process called "immortalization." In a final, Dr. Strangelovian twist, the cell lines--a cross-section of humanity kept alive in petri dishes--would be stored in genetic repositories around the world.

Some of the preliminary findings have proved controversial:

- After analyzing thousands of DNA samples collected in smaller studies, experts are amazed at the genetic unity that binds our diverse, polyglot species. Any two people, regardless of geography or ethnicity, share at least 99.99 percent of their genetic makeups--a deep sameness that makes a mockery of racist ideologies such as Nazism.

- Paradoxically, the minuscule .01 percent of our genome that does make people different doesn't shake out along visible racial lines. Instead, some 85 percent of human genetic diversity occurs within ethnic groups, not between them. The traits that so polarize our culture--the shade of our skin, the shape of an eye, hair texture--actually hide a dazzling and unexpected molecular tapestry that reflects our true origins. The European gene pool, for example, carries the story of where its members came from--and where they later migrated. It is a swirl of 35 percent African genes and 65 percent Asian genes.