Buzz
A DNA database helped investigators track down the Golden State Killer suspect by analyzing genetic data uploaded by his distant relatives. Now, population genetics researchers have calculated the likelihood that your family members have contributed their genetic information to a similar database.
Their findings suggest that most of us would likely have several third cousins in a 1-million-person database, around a hundred if the database holds 5 million records, and more than 200 in a 10-million-person database. In any of these scenarios, the probability is nearly 100 percent that the database contains at least one person related to you, whether it's a fourth cousin or further.
GEDmatch, the database used by law enforcement in the Golden State Killer investigation, has roughly 650,000 records. AncestryDNA boasts about 5 million, while 23andMe has around 2 million. (These figures were compiled by genealogist Leah Larkin last year.)
Though larger databases are not currently being utilized by law enforcement for DNA searches, as they only accept spit samples rather than data files, the growing interest in genealogy suggests these numbers will continue to rise, making it important to monitor these developments.
Considering these calculations, it’s quite likely that most people have distant relatives in GEDmatch, and probably some closer ones in AncestryDNA and 23andMe as well.
These numbers come with significant limitations. They assume the populations in these databases are randomly selected from the general population, which they likely are not. (I would wager that these databases lean toward white, wealthy, and Mormon individuals.) They also assume no inbreeding and that people randomly choose their partners. Lastly, these are averages; it's possible you might not have any relatives involved in genealogy, or conversely, your mom and sister might be actively working on the family tree and have persuaded all your relatives to join in.
However, according to scientists, the key takeaway is that the discovery of a suspect’s family DNA in a public database was likely not a stroke of luck but rather an entirely foreseeable outcome.
