"Some companies are starting to recognize that," she said. "There has certainly been an effort by a number of companies in the last year or two to be a little bit more cautious about what they tell people and qualify what they tell consumers."

Linking the world

More than two dozen companies now market "genetic ancestry tests," and more than 460,000 people have purchased those tests in the past six to seven years, the scientists' letter said.

Bolnick advises consumers to learn more about the science of DNA testing so they can better understand the results they receive.

"People should look at the information that's available on the Internet before making the decision to spend money on a particular test," she said. "There are very good sources out there, and they can help newcomers really figure out whether a particular test would be useful for them, given the questions they have."

Though the number of companies in the genealogy industry is growing, few do their own actual laboratory DNA testing.

Much of the DNA testing for the top genealogy companies is done in Utah at the Sorenson Genomics laboratories in South Salt Lake. The company does testing in three areas: forensics science, paternity and relationship testing, and ancestry DNA, said chief operating officer Douglas Fogg.

Fogg said the goal of the lab is to fulfill the dream of its founder, the late billionaire inventor and medical entrepreneur James LeVoy Sorenson.

"Mr. Sorenson's passion was to leave behind a legacy of peace," Fogg said. "That legacy was based on helping diverse cultures of the world understand how closely they are related biologically, and then perhaps they would treat one another with a little more civility."

Sorenson created the Sorenson Molecular Genealogical Foundation, and Sorenson Genomics was a laboratory formed primarily to process the samples that were being collected from around the world. The lab does a DNA analysis of those samples and sends the samples to the foundation for its genetic database.

The foundation, located on the same block as the Genomics lab in South Salt Lake, contains one of the largest correlative genetic and genealogical databases, Fogg said.

The foundation has collected approximately 100,000 DNA samples from 172 countries around the world, according to chief scientific officer Scott Woodward. He estimated the foundation has spent tens of millions of dollars developing its database and testing procedures in order to have the most accurate information available.

Funding for the nonprofit foundation's work comes primarily from the Sorenson Legacy Foundation, the charitable arm of the Sorenson Companies.