The function of DNA tests

Having listened to a recent episode of The Curious Cases of Rutherford and Fry (highly recommended, btw) which deals with DNA testing, one thing in particular struck me: when the red-headed Dr Fry was receiving her test results, her first question was “Am I a Viking?”

Not until she received a firm negative did she ask “Am I descended from Vikings?” (As presenter of a factual podcast, she must expect a fair amount of pedantry in general coversation, after all.) But asking about her genetic inheritance – rather than herself in the present – was her second question. And this is the strange thing about DNA tests which claim to reveal where in the world our ancestors came from – the results affect our own perceptions of self.

There are a number of issues around the recent boom in companies which analyse your DNA through a sample of saliva or blood, and produce a set of results which link you to various parts of the world. One is the scientific accuracy; the genetic pool against which you are measured is current, not historic, usually based off the company’s own data from test users worldwide, and in our current era of global mobility there is no guarantee that being linked to other users in a particular location means that your ancestors originated there. Instead, you and the group of people now resident in that location may share a common set of ancestors who lived somewhere completely different. Moreover, given variations between databases, different companies will give you different results.

A world map presented graphically through multicoloured circles

Another issue – recently highlighted by the high-profile identification of the Golden State Killer – is that by sending your DNA to these companies, you are effectively selling it to them, and paying for the privilege. Once they have tested your DNA, many companies retain the right to keep it. When it comes to catching serial killers, the ends may justify the means, but given the amount of information encoded within our DNA, the potential uses for these vast and expanding collections are myriad and often concerning from the point of view of individual privacy. In the case of the Golden State Killer, a family member had inadvertently exposed him by uploading her own genetic profile to a database, demonstrating that an individual sharing their own information by implications shares the information of their family, without the need for their permission. The ethical quandries mirror the issues of data privacy in social media sites, particularly cases of parents sharing information about their children without their consent.

So DNA tests are not necessarily an accurate way to tell where your ancestors lived, and there are some ethical grey areas around the way they use our genetic information. But leaving that aside – this is not a scientific blog, after all – what do DNA tests really do? What is the point?

Image from Wikimedia:
DNA strand. Image from Wikimedia:

DNA tests are, in many ways, the epitome of the intersection between heritage and identity. Our DNA is an in-built, personal record that has come directly from our ancestors. It affects everything from our appearance to our risk of developing illnesses or whether or not we like those sprouts served with Christmas dinner. For people who have been adopted, and have no strong genetic link with the family they grew up in, DNA testing may be a way to find out where their height, eye colour, or even a hereditary health condition came from.

But it is more than that. Without any real scientific evidence, we believe that our genes influence our personality, behaviour, likes and dislikes. Redheads are popularly believed to have a temper, the Welsh are naturally musical, the Irish like drinking alcohol. For people who are not brought up in any cultural context which would instill such characteristics, claiming a genetic heritage from a particular place gives them a claim on that culture – a particularly notable characteristic among modern Americans, for whom a combination of ancestors from around the world make genetic heritages a normal part of individual identity.

There are a lot of potential links here to pseudo-sciences like phrenology (which claims to read your personality and intelligence levels from the shape of your skull), or even darker forms of prejudice which suggest that certain genetic inheritances make people naturally less intelligent, trustworthy, etc. etc. There is a need for caution in linking genetics to personality traits. Yet still the popularity of DNA testing shows that the need for people to situate themselves within a context of inheritance; an explanation which allows them to feel that their own personality quirks are simply a reflection of belonging to a particular culture, not a marker of difference from their peers in the present.

But the most extraordinary function of a DNA ancestry report is the way it might change an individual’s own perspective on themselves. Without knowing about any familial connection to a particular place or culture, there is no way a person can have inherited cultural knowledge or traits. But the belief that our ancestors shape us in ways that we cannot yet read in our DNA is strong, and means that a previously unknown genetic link to place someone may never have visited will give that person a sense of connection with the place. Someone whose ancestors originated in Scotland might suddenly feel a sense of personal injustice over the Highland Clearances; someone who discovers a genetic link to the Middle East might pay more attention to the political situation nearby.

We believe that DNA tests can tell us things about our personality that we ourselves didn’t know. This demonstrates that, at a fundamental level, our own inheritance, that we inhabit in our own bodies, is a guiding force in our lives and the root of much of our own sense of identity, the belief that we have a community to which we belong. Family, far beyond those we know, are at the heart of our own sense of self.

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