About 60 percent of Americans with Northern European heritage are now identifiable from their DNA by just using genealogy databases, whether or not they have made their genetic information available, findings of a new study have revealed.
Researchers of the study said that the number of people identifiable through these databases is expected to grow as an increasing number of people upload their DNA profiles to websites such as 23andMe, which use genetic analysis to find a person’s relatives.
These genetic databases have already been used for criminal investigations. In April, authorities announced that they used a genetic genealogy website to connect DNA found in crime scenes to a man alleged to be the Golden State Killer, who committed at least 13 murders, over 100 burglaries, and more than 50 rapes from 1974 to 1986.
For the new study, which was published in the journal Science on Thursday, October 11, Yaniv Erlich, from Columbia University, and colleagues analyzed the DNA profiles of 1.28 million participants on the website, MyHeritage, most of whom have Northern European genetic backgrounds. The researchers then looked for relatives more distant than first cousins elsewhere in the database.
The Associated Press reported that about 60 percent of the time, Erlich and colleagues found somebody whose genetic similarity was equal to that of a third cousin. This is similar to the degree of relatedness that led investigators to the Golden State Killer. Third cousins are individuals who share a great-great-grandparent.
Searches typically start on a genealogy website by finding a relative associated with a DNA sample. Sleuths can then use other information, such as publicly available family trees, public records, list of survivors in obituaries, and other information that they can gather about the person who owns the DNA.
Using these information, investigators can then build their own speculative family trees and identify someone whose DNA matches the original sample.
Erlich commented just how powerful these DNA databases are. He explained that it only takes a small portion of the population to identify more people as each person in a DNA database serves as a beacon that illuminates hundreds of distant relatives. Once distant relatives are found, an anonymous DNA can lead to a specific person.
“Usually, we think about paternity tests, you can find the father, you can find siblings, but with the advance of more powerful techniques in genomics, you can now actually identify third cousins, even fourth cousins in some cases,” Erlich told CNN.