Even as consumers embrace commercial genetic ancestry tests to trace ancestral roots or fill in gaps in the family tree, a team of researchers today (Oct. 19) is urging buyers to use caution when interpreting test results.

The tests have significant limitations, say the authors of an articled entitled "The Science and Business of Genetic Ancestry Testing," which appears in the Oct. 19 issue of Science.

"These tests promise more than they can deliver," said Jenny Reardon, assistant professor of sociology at the University of California, Santa Cruz, one of 14 researchers from universities across the nation who coauthored the article. "They are being marketed as 'recreational,' but many consumers do not take these tests lightly."

The tests raise serious questions about how societies define race, and they can have profound impacts in terms of personal identity and the allocation of resources, said Reardon.

Consumers have varied and often deeply personal reasons for taking the tests, which typically cost between $100 and $900, according to the authors. Some hope to validate genealogical records, fill in gaps in family histories, or find connections to specific groups or places, while others have used the tests in hopes of tracing ancestral links lost during the slave trade or to establish Native American tribal affiliations, or challenge tribal membership decisions. Since 2001, more than 460,000 people have purchased the tests.

"Not all the companies that market these tests spell out their limitations, yet the results can have serious consequences," said Reardon, the author of Race to the Finish: Identity and Governance in an Age of Genomics (Princeton, N.J.: Princeton University Press, 2005). Based on genetic test results, people have relocated and made other major life-changing decisions, said Reardon.

The coauthors argue that the assumptions and limitations of the tests make them less informative than many realize, and commercialization has led to misleading practices that reinforce misconceptions. The authors call upon the scientific community to better educate the public about the limitations of the tests and to develop policy statements that make clear the limitations and potential dangers of genetic ancestry testing.

Some of the tests' limitations discussed in the article include:

. Most tests analyze only a small portion of an individual's DNA and trace only a fraction of an individual's ancestry;

. Test results are based on incomplete databases of samples gathered around the world; as databases grow, results are likely to change over time;

. Most companies consider results proprietary, which hampers public access to the broadest-possible database that would yield the most comprehensive findings;

. There is no clear-cut connection between DNA and racial/ethnic identity.

"Because these tests are purportedly scientific, they suggest that race is a biological issue that can be determined by looking at genes," said Reardon. "However, if someone who considers herself white takes a test that suggests she is of 10-percent African ancestry, does that make her African American? How should she report her race on governmental forms or college and job applications? Genetic ancestry testing raises bigger issues about how we define race, and those issues need to be on the table."

"These tests are not recreational at all," said Reardon. "They require greater scrutiny and oversight before being sold to the public."

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Note to reporters: Reardon can be reached via e-mail at reardon1@ucsc.edu.