Who’s your (ancestral) daddy? Family tree genetics might link everyone to King David

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Look into my crystal ball and I will show you where you come from. Who do you see? Charlemagne? Gengis Khan? King David? Wilt Chamberlain? Well, Adam Rutherford reporting at the BBC thinks a crystal ball might be just as good as direct-to-consumer genetic testing when it comes to the ‘genetic astrology’ of linking the DNA of modern humans to their famous ancestors.

Khan and Charlemagne are two of the famous historical figures linked to by these tests because of their reputed fecundity. Most European men can chart their genetic history in some regards back to a single person who lived during the time of the Holy Roman Emperor Charlemagne just as tens of millions of men–as many as 1 in 200 worldwide–can trace their ancestry to a single man who lived during the time of Kahn–likely the Mongol leader himself. (Chamberlain is just a joke.) If you go back far enough in time, we are all related, sharing distant common ancestors.

It’s not that special, says Rutherford. There are legions of these relatives:

This is merely a numbers game. You have two parents, four grandparents, eight great-grandparents, and so on. But this ancestral expansion is not borne back ceaselessly into the past. If it were, your family tree when Charlemagne was Le Grand Fromage would harbour more than a billion ancestors – more people than were alive then. What this means is that pedigrees begin to fold in on themselves a few generations back, and become less arboreal, and more web-like. In 2013, geneticists Peter Ralph and Graham Coop showed that all Europeans are descended from exactly the same people. Basically, everyone alive in the ninth century who left descendants is the ancestor of every living European today, including Charlemagne, Drogo, Pippin and Hugh. Quel dommage.

One company even claims the ability to pinpoint the exact location of you ancestral village, for example. But what they’re actually selling is a geographical representation of your genetic diversity according to your DNA, not the true account of the history of your family. If an analysis indicated you’re German and English, for example, your village maybe marked as in Belgium, but that does’ mean your genetically Belgian. At least one customer was disappointed when her ‘village’ was found to be at the bottom of a river, according to Rutherford.

In another example, Rutherford discusses a business that claims to be identifying the unique genetic profile of the Welsh people, though direct-to-consumer genetic test kits. Of course you must buy one to participate. Beyond scamming people out of their money, the idea that DNA could be fundamentally Welsh, or any nationality, is deeply flawed because the establishment of countries is a political construct overlaid on people just as it is overlaid on the geography of the land, Matthew Thomas writes at BioNews:

I especially enjoyed the section about Cymru DNA, shown on Welsh-language TV station S4C. This show and the ancestry company behind it, Cymru DNA Wales (owned by the controversial Britain’s DNA), purported to link Welsh celebrities to spurious ‘types’ of DNA – for example, weather forecaster Sian Lloyd has a ‘foraging’ genome, while Plaid Cymru’s former president, Dafydd Iwan, was sycophantically labelled ‘ancient Welsh’. The representative from the show’s production company hid behind the excuse of ‘commercial sensitivity’ to avoid discussing the details of the research. [Mark] Jobling made an important point here about how talking of ‘quintessentially Welsh’ genes is ‘rank nationalism at work’. As Rutherford told us: ‘DNA doesn’t tend to reflect national boundaries.’

There are, however, important circumstances where these ancestors tests are incredibly valuable: identifying close relatives. Although they are rather bad at predicting our ancient ancestors, they link living or recently living relatives to us with great reliability if you test for enough DNA marker. And, there are many reports of people locating long lost family members or establishing questionable paternity using these tests.

Related article:  DNA, the 'devious defecator' and the right to genetic privacy

If Rutherford is right and these tests are completely useless, why do people buy them? Public health experts Scott Bowen and Muin Khoury at the CDC had the same questions about genetic data regarding health: why do people continue paying for these test when there are so few ‘slam dunk’ cases for genes and health?

I think, in both cases, the answer lies in a pervasive cultural desire to better know anything about yourself, whether it is evidence upon which you could base a healthcare decision or connect with long lost family members. It’s the same impulse that leads many of us down the clickbait trail of ‘Which fast food restaurant are you?’ and ‘Which Disney princess would you be?’ quizzes on social media. We are constantly looking to explain ourselves.

Because our experiences are so subjective, measuring our genes seems like a natural place to start. Are direct-to-consumer genetic testing companies exploiting this desire? Of course they are, but so is every other marketing department in the country. Our love of celebrity is also at play.

There is another school of thought that suggests even at the “nearly meaningless” level, the Charlemagne connection for example, shared lineage and maybe even shared experience–the invocation of ‘family’–makes us better people, writes Jesse Rifkin at the Daily Beast:

Evidence suggests the best way to change hearts and minds may be not through numbers or facts, but through family. A Harvard University study last year found that male judges with daughters were more likely to vote in favor of women’s rights in judicial cases than judges with only sons. Support for same-sex marriage increased substantially in the past decade among those with a family member who came out, while remaining virtually stagnant among those who hadn’t. Sen. Rob Portman of Ohio, the first incumbent Republican to back same-sex marriage in 2013, cited his gay son as the turning point in his opinion.

Right now, ancestry testing doesn’t offer much beyond a fuzzy portrait of our ancestors or a few ties to relatives born after the invention of the Model T. But for some reason that information is vital enough in our culture to support several multi-million dollar companies. As Rutherford cautions (audio) consumers, take it with a grain of salt:

Genetics is messy, and history is foggy. We are a species that is mobile and horny. Throughout history we have moved around, outbred, inbred and sewn our seeds. Everyone of your ancestors lived somewhere and had sex at least once. In doing they created a picture of your past that is murky, never straight forward, but beautifully complex.

Meredith Knight is a contributor to the human genetics section for Genetic Literacy Project and a freelance science and health writer in Austin, Texas. Follow her @meremereknight.

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