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'The Ugly Truth'

by Tracey Brown, director of Sense About Science

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Genetic Ancestry Testing

Read our guide Sense About Genetic Ancestry Testing

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Part of a rapidly growing market for genealogy, commercial ‘genetic ancestry tests’ offer people a profile of their genetic history based on a DNA sample for around £200. The test findings tell people that they have links to groups such as Aboriginals or Vikings, to particular migrations of people and sometimes to famous figures such as Napoleon or Cleopatra. But genetics researchers warn that such histories are either so general as to be personally meaningless or they are just speculation from thin evidence.

Our guide explains why DNA tests are used in population research and why they do not provide accurate information about an individual’s ancestry:

  • Our individual ancestry is much shallower than people might imagine – the best estimate is that the most recent person from whom everyone alive today is descended lived just 3,500 years ago.
  • As we look back through time we quickly accumulate more ancestors than we have sections of DNA, which means we have ancestors from whom we have inherited no DNA.
  • There are millions of possible ‘stories’ of your ancestry. To know whether any one of them is likely to be true, it would need to be tested statistically for its likelihood against other possibilities.
  • The genetic ancestry business uses a phenomenon well-known in other areas such as horoscopes, where general information is interpreted as being more personal than it really is.

The proliferation of companies obtaining DNA data from people interested in ancestry or disease profiles has raised serious concerns about privacy and openness about the use of these data. These are described in an award winning article in Scientific American.

Some comments from genetic scientists:

David Balding, Professor of Statistical Genetics, UCL Genetics Institute: "Be wary of news items about genetic history - that someone famous is related to the Queen of Sheba or a Roman soldier.  Often these come from PR material provided by genetic testing companies and can be trivial, exaggerated or just plain wrong. Genetic relatedness isn't very meaningful beyond a handful of generations away, because the amount of DNA you share with a very distant relative is negligible compared with the huge amount of DNA we all share from our common ancestors." 

Mark Thomas, Professor of Evolutionary Genetics, Department of Genetics, Evolution and Environment, UCL: "Ancestry is complicated and very messy. Genetics is even messier. The Y chromosome and mitochondrial DNA contain little information about an individual’s ancestry. The idea that we can read our ancestry directly from our genes is absurd. In recent months there has been a spate of newspaper, TV and radio stories about famous people being descended from other famous people, or cool groups like Vikings. But these claims are usually planted by the companies that provide these so-called tests and are not backed up by published scientific research. This is business, and the business is genetic astrology.”

Professor Mark Jobling, Professor of Genetics, University of Leicester:  “Over-interpretation is always a pitfall in studies of genetic history, and particularly so when the history is of individuals. Some suppliers of individualised tests have been guilty of telling punters what they want to hear, by spinning implausibly specific stories about ancestry, such as Viking or Celtic origins for their Y chromosome or mitochondrial DNA. Information and demystification is clearly needed.”

Tracey Brown, Director, Sense About Science: “Genetics researchers are telling us that you are better off digging around in your loft than doing a DNA ancestry test if you want to find out about your family tree. We tend to see DNA tests as providing specific personal information, because of their use in crime detection and medical diagnosis. The genetic ancestry business trades on this.” 

Steve Jones, Emeritus Professor of Human Genetics, Evolution & Environment, UCL: “On a long trudge through history – two parents, four grandparents, and so on – very soon everyone runs out of ancestors and has to share them. As a result, almost every Briton is a descendant of Viking hordes, Roman legions, African migrants, Indian Brahmins, or anyone else they fancy.” 

Lounes Chikhi, CNRS Senior Scientist (Directeur de Recherche) at the Evolution and Biological Diversity lab, Paul Sabatier University, Toulouse, France: "The interpretation of genetic data is already difficult where geneticists try to reconstruct aspects of our recent evolutionary history, and becomes desperately so when we try to do the same for specific individuals. Unfortunately, many claims made by ancestry companies are closer to ‘folk genetics’ than real population genetics. Everybody wants to be related to Genghis Khan or the Vikings (well I actually don't). The good news is that they all probably are."

Mike Weale, Reader in Statistical Genetics, Department of Medical and Molecular Genetics, KCL: “I know it’s only a tiny part of my true ancestry, but I would still love to know whether my male line ancestors were Vikings, or Celts, or both, or neither.  Or at least be reasonably certain.  Same goes for my female line.  It’s a shame there’s no valid way to do that.”

Press coverage

Daily Express Your tongue can tell of a Viking past

BBC Some DNA ancestry services akin to 'genetic astrology'

The Telegraph DNA ancestry tests branded 'meaningless'

The Telegraph Are you related to Cleopatra? Or are genealogists fishing in the Nile?

The Daily Mail Expensive tests claiming to trace person's ancestry are as dubious as astrology, warn scientists

Which? Would you pay for proof that you’re related to Attila the Hun?


Sense About Genealogical Testing