"They took the science and they bastardized it"

Don't expect all your genealogical conundrums to be solved with a simple DNA test:

As ads go, they're pretty alluring: "Find out how you are related to Marie Antoinette" and "Discover your relation to Genghis Khan." With a simple swipe of a swab inside the mouth, consumers are told, they can capture DNA for analysis to trace their ancestors and country of origin.

But researchers say genetic ancestry tests being offered by a growing number of companies have significant limitations in pinpointing a long-dead relative on the family tree or tracking down geographical roots.

"These tests all examine a very small fraction of the DNA in your body and the result is that they can only tell you something about a few of all of your ancestors," said Deborah Bolnick, lead author of a paper on the issue published Friday in the journal Science.

"I think it's just important for consumers to be informed about what the test can and cannot do," said Bolnick, an anthropologist and geneticist at the University of Texas in Austin.