Illustration by Polly Becker: Writer Rebecca Skloot (center) turns to DNA to track down a broken branch in her family Tree. Illustration by Polly Becker

It all started, as so many quests do, on the Internet. Just a random link on a random Web site, but something made me click it. And before I knew it, I was scrolling through what felt like an online genealogic red-light district, a sensory overload of temptation and promises of fantasies fulfilled: "Use DNA to illuminate the past and bring ancient ancestry to life" ... click ... "The only way to know where you come from is by reading your DNA" ...
click ... "Are you adopted and curious about your heritage? Recent advances in genetic testing have put the answer to questions like these at your fingertips" ... click ... "See if you have a long-lost relative" ... click ... "Identify your ethnic and geographic origins, both recent and far distant."

For anywhere from $219 to $1,200, depending in part on the level of accuracy I required, companies such as Oxford Ancestors and Genelex were offering to trace my family back thousands of years to a remote prehistoric mother, to tell me precisely which ethnic groups I belonged to and in what concentrations -- whether, for example, the blood of Native Americans, Jews or Vikings ran through my veins. One company promised -- for no additional charge -- to use my DNA to put me in touch with "Genetic Cousins" I never even knew I had.

As fantastical as these come-ons sounded, for some reason
I kept clicking on one link after another. What can I say:
I am -- at least as much as any other American mutt -- a
sucker for any information that might patch a hole or two in my family history. And as it happened, I'd just learned of one intriguing personal genealogical mystery I was interested in solving. So I kept on exploring.

On the other side of those links I found companies whose advisory boards were packed with seriously credentialed scientists -- population geneticists, molecular anthropologists, you name it -- from prestigious universities. To back up their claims, the companies linked to research published in
highly respected peer-reviewed journals like Nature and
Science and media reports from The New York Times and Nova. And I thought, Huh, maybe there's some legitimate science here.

So I picked up the phone.

Hey, Mom, I said, will you send me some of your DNA?

Until the dawn of the internet age, a person trying to create a family heritage map, fill gaps in a family tree, or even answer a single question about an ancestor generally followed the model of my distant cousin Les Hickenbottom. He has spent much of his retirement at genealogical gatherings -- surrounded by people whose RVs sport "I Brake for Graveyards" bumper stickers -- or in various courthouses and city halls around the country, sifting through birth, marriage and death certificates, wills, land deeds, and court records, panning for any information he can find about our family. This approach is known as paper-trail genealogy, and the Internet has made that trail (in digital form) dramatically easier to follow: The National Archives put 50 million documents online in April 2003, and when Ellis Island posted its immigration files on the Web in April 2001, the site received eight million hits in the first 6 hours.

But you can't digitize what doesn't exist, and sooner or later most genealogical hobbyists hit an unbreachable gap in the historical record, a place where the paper trail simply vanishes: Last names change, people move, adopt, disappear. Suddenly, there are no more documents to follow -- history seems to stop dead in its tracks. It's what genealogists call a brick wall in the paper trail.