I must admit personally to being very fond of genetic genealogy. That is not to say that there are not risks that genetic information could be misused by someone, but only that the ease of finding DNA for someone if others want to find it means that one might as well gain the use of it for good because if people are willing to gather your DNA from the traces you leave, they are going to find it anyway in some fashion. To be sure, it does take a certain amount of boldness in deliberately placing your DNA in places where it can be recognized easily. My own DNA, for example, has been submitted to Y-search from FTDNA, through Ancestry.com, and in GedMatch, so if someone wanted to match my DNA it would be a trivial task to do so. Nonetheless, there are legitimate reasons why someone might be concerned about the popularity of genetic genealogy, because it allows for one’s sins to be found out in rather striking fashion. How is this the case? Let us count the ways.
One of the more obvious ways that one’s sins can be found out using genetic genealogy is through the problem of not parent expected events. When your DNA is examined, if you match with people you match for a reason, namely shared ancestors, especially if the DNA shared is over a somewhat long distance. While very small amounts of DNA can be shared by very distant relative, once you have a sufficiently long segment to draw serious attention, that is going to come from sufficiently recent common ancestors to make it well worth one’s while to investigate. If you have certain DNA and it is found that your supposed paternal relatives do not, they are not your paternal relatives. If you find yourself with DNA matches you have never heard of that are half-siblings, then your mother likely was playing a game of Hoosier daddy and some further awkward family conversations are in your future. The same thing can happen in previous generations, and the reasons are roughly the same. Where you find adoption or affairs leading to pregnancies, these are precisely the sorts of sins that one would expect to find one out.
It is easy to see why people would be less than enthusiastic about this sort of thing. If someone has reason to suspect that they may have a secret family of some kind, then the last thing they want is for their children to be discovering their half-siblings. Half-siblings share 25%, give or take a few percentage points, of the same DNA, so that would be an obvious and very high match. To speak from my own experience, my own high-rated DNA matches are all close relatives who can be easily placed in my family tree, including my brother, my only paternal first cousin, a great-aunt, and a couple of first-cousins once removed, many of which I know personally. And if a family that is fairly active like mine in genetic genealogy can only have a few really close relatives, those who have something to hide are not going to want to encourage large amounts of potential genetic matches waiting to send each other uncomfortable messages and planning emotional reunions with unknown families.
Yet there are even more profound and painful ways that genetic genealogy catches people out in their sins. Let us look at the example of the Golden State Killer. For decades a variety of women were raped and murdered in different parts of California and the police were completely unable to figure out what was going on, to the point where random sleuths wrote books talking about the patterns and expressing hope that these cases would be solved. Yet the solving of the case ended up involving genetic genealogy when a close relative of the perpetrator’s DNA was found on commercially available genetic genealogy mentions, thus dramatically narrowing the pool of people who charge with the crimes. When one combines the ease of gathering DNA from people with the massive amount of people who could be uncovered through genetic genealogy, a lot of cold cases have the potential to be solved as long as the physical evidence has been properly stored.
All of this ought to lead us to ponder how it is that contemporary genetics and the immense popularity of genetic genealogy should make us pause when it comes to our behavior. If someone did not want their own DNA to be accessible to find and to be matched with, would it be reasonable to assume that people would be able to discourage the practice among those sharing the same great-grandparent? It is a somewhat trivial task to match people who share DNA on the level of second cousin or closer, and when one has a large enough family, triangulating segment matches on that level is not going to be hard for any forensic geneticist worth his or her salary. The rising popularity of genetic genealogy makes it increasingly likely that many people will be close matches regardless of how much they want their own genealogy to be hidden. In a world like our own, as long as you leave DNA traces of your sins, they will find you out. Just live accordingly.