By all accounts, that certainly wasn't the idea back in 1991 when a handful of the brightest geneticists dreamed up an almost biblical plan to safeguard, at least in test tubes, the fading kaleidoscope of human diversity.

Writing an impassioned open letter in the journal Genomics, the researchers warned that if the story of our species is embedded within the genes of living populations, then "the gate to preserve these clues is closing rapidly."

Why?

In essence, scientists can't reconstruct our family tree if there are no branches: The small, isolated populations that make the best subjects for diversity research are slowly disappearing.

Five centuries of European colonization, anthropologists say, have snuffed out countless small ethnic groups through disease, intermarriage and outright genocide.

Today, mass culture is rapidly steamrolling much of the diversity that remains--most of it clustered within the DNA of tribal minorities whose gene pools offer clear glimpses back to Paleolithic times. With the lure of pop culture and vast migrations to urban melting pots, the subtle palette of humanity is being muddled by assimilation--and with it the picture of our past.

A thumbnail measure of this homogenizing trend is the death of the world's languages, which are loosely associated with genetic distinctness. By one estimate, fully 90 percent of the 5,000 tongues that are still used--most of them spoken by tribal peoples--will vanish within the next century.

That, scientists hope, is where the diversity project comes in.

"The idea is to have colleagues on each continent sample the populations that wish to cooperate and then pool the data globally," said Cavalli-Sforza, a principal author of the 1991 call to arms and one of the intellectual fathers of the global gene survey. "Nobody gets rich off of this, nobody oppresses anyone. It's a shared, open resource for all humanity."

Click for an explanation of automated DNA sequencing graphic.

How, exactly, would Cavalli-Sforza's DNA survey offer a window into history?

Inside each one of our cells lie coiled the 3 billion nucleotides--or molecular rungs--that make up the spiral ladder of DNA, the blueprint of life. During the course of evolution, random and mostly harmless flaws called mutations accumulate in the ladder, and it is this record of glitches that allows scientists to track our ancestry--much as a unique surname can be traced through time by genealogists.

First, geneticists identify the most stable of these mutations, called gene markers, in populations around the world. Archeological evidence is then marshaled to date the ancestry of the peoples who carry those markers. By merging both sets of data, scientists can bring to light unexpected connections between peoples.

DNA markers associated with Middle Eastern peoples, for example, have been discovered in a clear south-to-north gradient across Europe. They are the faint molecular footprints, experts say, of prehistoric farmers who brought agriculture to Europe from Asia Minor thousands of years ago--genetic echoes that linger in the DNA of French businessmen and German housewives.

Mapping markers, though, tells only half of the human story. Scientists also are working to perfect "genetic clocks" that measure the mutation rates in DNA to time when our ancestors last diverged and went their separate ways.

With both of these tools, the entire pageant of human history lies waiting to be read in every drop of blood or in the root of a hair or in a scraping of cells from a cheek.

Click to see enlarged map of genetic migration.

Here is a sampler of some recent "genography" discoveries:

- A comparison of gene markers worldwide supports the Out of Africa theory of human evolution, which holds that modern humans first migrated out of Africa barely 100,000 years ago--an evolutionary blink of the eye--during which most racial features emerged. Because Africans' genetic roots penetrate at least another 100,000 years deeper into the soil of Africa, they have had more time to diverge genetically than other populations. Far from being a monolithic race, Africans are the most genetically varied peoples.

- The DNA of Native Americans, whose genes reveal hidden links with an ancient homeland somewhere near Mongolia, indicates that the famed Bering Straits crossing occurred between 15,000 and 30,000 years ago, far earlier than archeological evidence suggests. DNA testing on both sides of the waterway also hints at reverse migrations of Native Americans back into Siberia, findings supported by linguistics.

- In Europe, DNA tells us that the Basques are the oldest residents of that continent, with a lineage that stretches back 30,000 years to Cro-Magnon man. At the other end of the time line, Finns appear to be among the youngest Europeans: Their genes traveled north with a small band of Middle Eastern people as recently as 4,000 years ago. Settling in the forests of sun-deprived Scandinavia, they quickly lost their ancestors' coppery complexions.

- Genetic surveys in Japan debunk the widely held notion that the Japanese are a single, unvarying ethnic group. Markers on the male Y chromosome show that the island-nation's populace are an admixture of two ancient tribal peoples whose homelands lie near Mongolia and the Korean Peninsula.

While these discoveries have intriguing implications for people fascinated with roots, they can still smack of musty academia--the stuff of faculty lounge debates.

But the awesome power of DNA technology is changing that, thrusting even the dimmest episodes of history into the realm of daily life, making them immediate and personal as never before.

One example is Michael Hammer, a young geneticist at the University of Arizona. He made headlines recently by showing that the DNA of Cohanim--the Jewish priesthood whose duties are passed strictly from father to son--is indeed genetically distinct from the rest of the Jewish population.

Hammer's discovery has sent shivers of unease through some ultra-orthodox Jewish communities. What if--priests are asking--we don't carry Cohanim gene markers?

Even more remarkably, Hammer hopes with additional sampling to track the entire lineage back 3,300 years to Aaron, the brother of Moses who founded the priestly caste.

"A decade ago, we started with maybe 100 good genetic markers, but now we have thousands," said Hammer, a soft-spoken researcher who is as casual in black jeans and silver earring as Cavalli-Sforza is aristocratic. "The picture of who we are becomes clearer all the time."

Dreamily, Hammer ticked off some other major quests of diversity research: reconstructing the human diasporas that settled Polynesia, plumbing the roots of India's caste populations and digging back through the double helix to find the ancient homelands of African-Americans.

Noting that scores of molecular sleuths are turning up markers faster than journals can publish them, Hammer added puckishly, "We're going to have some amazing stories to tell."

Actually, with cutting-edge technology that automatically replicates and sequences vast chunks of DNA at speeds unimaginable even five years ago, the number of markers waiting to be discovered could theoretically mushroom into the millions.

The upshot?

With that astonishing degree of resolution, any two people--Swede, Tibetan, Navajo or Tutsi--could trace their lineages back to a shared ancestor, whether 5,000 or 50,000 years ago.