Nine years ago, improved technology revolutionized the science of genealogy through DNA testing, making the procedure of tracing one's genealogical lineage easier in many ways and creating a new industry in the process.

While the science is progressing rapidly, so is the business of DNA testing for genealogy, and two Utah companies, GeneTree and the Generations Network, have become industry leaders. But researchers are telling buyers to beware.

This past fall, 14 researchers from across the nation wrote a letter that was published in Science magazine, warning that "both scientists and consumers should approach genetic ancestry testing with caution."

"The tests can have a profound impact on individuals and communities; the assumptions and limitations of these tests make them less informative than many realize; and commercialization has led to misleading practices that reinforce misconceptions," the researchers said. "Many consumers do not realize that the tests are probabilistic and can reach incorrect conclusions."

The tests cannot pinpoint the place of origin or social affiliation of even one ancestor with exact certainty, and they should not be seen as determining the race or ethnicity of the test-taker, the scientists wrote.

Harvard University professor Henry Louis Gates Jr. has also expressed concerns, saying that consumers should supplement DNA testing for genealogy with historical research. Gates, who is director of Harvard's W.E.B. DuBois Institute for African and African American Research, recently launched a new company called AfricanDNA that helps blacks trace their genealogical roots.

He said the company was developed, in part, because a company that tested his DNA told him his maternal ancestry was of Nubian descent from Egypt. He later discovered through further genetic testing that his maternal lineage was most likely of European ancestry.

One of the researchers who wrote the Science letter is Deborah Bolnick, assistant professor of anthropology at the University of Texas at Austin. She says consumers should understand the nature of the information they are getting through DNA testing.

"In certain contexts, it can be very useful and give you a lot of very specific good information," she said in an interview. "Some of the more important limitations have to do with the fact that we can really only trace a very limited number of your ancestors with the available DNA tests."

She said people should be aware that information becomes less reliable the farther back in history you go. Answers in DNA testing and genealogical research are often based on probability rather than absolutes.