With a swab of the cheek, DNA analysis is transforming genealogy.

Ancestral DNA tests weren't available a decade ago, but now they can be purchased from a variety of sources, usually for a few hundred dollars. The lab sends you a kit, and you send back a cheek swab or mouthwash. The analysis traces your origins throughout historical migration patterns and links you to other family members.

Bryan Sykes, professor of human genetics at the University of Oxford in England and author of "The Seven Daughters of Eve," has been studying ancestral DNA for 20 years. He says he's traced all living humans to one of 36 women living around the world tens of thousands of years ago.

"You can link up with other people who have same DNA fingerprint," he says. "A DNA test proves one way or another if two people are related." Bennett Greenspan, president of Family Tree DNA, says it's also valuable in showing who doesn't belong in your family tree.

He tested 55 men named Greenspan around the nation and discovered none of them shared his DNA except his immediate family.

"If I'd been researching their paper trails all these years, I'd know a whole lot about a Greenspan lineage that isn't related to me at all," he says.

The best method, according to Greenspan, is to test yourself and your most distant known cousin. "If you match, you've authenticated back to your common male ancestor," Greenspan says. "It's triangulating - using two locations to figure out where you are."

Most DNA tests can track either the male or female lineage. Scott Woodward, director of Sorenson Molecular Genealogy Foundation, says the next step is autosomal DNA, which tracks both sides of the family. No autosomal database has yet been published, though SMGF plans to make its initial research available soon.

"Our goal is to be able to take any two people in the world and demonstrate that they're not just connected, but how they're connected, their common ancestors," Woodward says. "This will change attitudes and the way people think about each other."

Even with all this, DNA research is only just beginning, and experts in the field say there may be no limit to where it can lead, particularly as more people are tested and databases grow. "Everybody has the history of the world written in their DNA," Sykes says.