/ Technology

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

DNA strand

For £200 you can get a DNA test that claims to tell you who your ancient ancestors were. But do these tests really work? Sense About Science explains why scientists are warning that these tests often aren’t worth it.

Commercial ‘genetic ancestry tests’ offer people a profile of their genetic history based on a DNA sample: you send off a sample of your saliva and the test findings may come back to tell you that you are descended from groups such as Aboriginals or Vikings, or related to famous figures such as Napoleon or Cleopatra.

Sounds great, but at Sense About Science, we don’t think these tests are what they claim to be.

Are commercial DNA tests accurate?

The tests are part of a rapidly growing market for genealogy, and ancestry is now big business. Thousands of people are taking DNA ancestry tests every year, with at least 40 companies offering tests internationally. They don’t provide accurate information about an individual’s ancestry, so people aren’t getting what they are paying for.

There are legitimate ways to look at personal genetic history (genetic genealogy), but these are based on much more than an individual’s DNA tests in isolation. They are based on databases of genetic information about many other people, historical records, information about surnames, and so on.

This is why Sense About Science has been working with genetics researchers to explain why commercial DNA tests cannot provide accurate stories about personal ancestry. This month we launched a briefing, Sense About Genetic Ancestry Testing, which comes with a warning: don’t be fooled by the appeal of an exotic lineage or a notorious ancestor.

Many of the claims about such histories are either so general as to be personally meaningless, or they are just speculation from thin evidence.

Finding out your individual ancestry

Our individual ancestry is much shallower than people might imagine. The best current estimate from genetics research is that the most recent person everyone alive today is descended from lived just 3,500 years ago.

And patterns of ancestry are complicated. As you look back through time you quickly accumulate more ancestors than you have sections of DNA. This means you have ancestors from whom you have inherited no DNA.

The genetic ancestry business uses a widespread phenomenon where general information is interpreted as being more personal than it really is (the ‘Forer effect’), similar to how horoscopes work.

The reality is that there are millions of possible ‘stories’ of your ancestry. To find out whether any one of them is likely to be true, you would need to use statistics to test its likelihood compared to other possibilities. Your DNA cannot be read like a book or the map of a journey. Ancestry is more complicated.

So are you descended from Vikings? You may well be… but so are many of us. Think before you part with your money: everyone’s interested in where they come from, but you might be better off to start by searching through your loft or chatting to your Grandma.

Which? Conversation provides guest spots to external contributors. This is from Tabitha Innocent, Scientific Liaison at Sense About Science. All opinions expressed here are Tabitha’s own, not necessarily those of Which?

Comments
Guest
Diana Payne says:
25 March 2013

How does this commercial process differ from those used on the recent Eddie Izzard documentary?

Guest
DebbieK says:
25 March 2013

The tests used on the Eddie Izzard documentary are the same as those used by commercial companies, though some companies provide a much wider range of tests and more advanced testing than was used in the programme. Most commercial DNA tests are actually considerably cheaper than £200 with prices starting from $39 (about £30). See the testing company comparison charts in the ISOGG Wiki:

http://www.isogg.org/wiki

While the DNA testing on the programme was accurate, the claims made about Eddie Izzard’s ancestry were not scientifically sound. The programme was wrong to suggest that Eddie Izzard is a Viking based on his Y-DNA and an Anglo-Saxon based on his mtDNA.

For the use of DNA testing for genetic genealogy see the blog post I wrote for Sense About Science “Sense about genealogical DNA testing”:

http://www.senseaboutscience.org/blog.php/41/sense-about-genealogical-dna-testing

Guest

If I go back 1,500 years, assuming my ancestors reproduced every 25 years or so, I will have around 1,000,000,000,000,000,000 to choose from.

I don’t need to spend £200 to tell me that my great uncle Atti will be in there somewhere.

Guest

If you went back 1500 years there’d be rather fewer than you think. The article contradicts itself in where in one sentence it says that “the most recent person everyone alive today is descended from lived just 3,500 years ago.” then in the next says “As you look back through time you quickly accumulate more ancestors than you have sections of DNA”

Everyone has two sets of grandparents. A few have three sets of great grandparents rather than four (parents are first cousins). Many more marry their second or third cousins and going back a few generations when communities were small and relatively isolated such marriages were far more common than now. It has been said that one of the biggest influences on human genetic diversity was the invention of the bicycle – ordinary youngsters could then get to the next town or village for free.

My point is that when most people go back relatively few generations the number of ancestors unrelated to each other becomes fewer rather then increasing exponentially as one might intuitively think.

Guest
Pete G says:
3 April 2013

Work your way back in your family tree until you can link into other people’s existing family trees which go back much further in time.

I did so on the genealogy website Geni, which, as a result, informed me upon request, for free and within 60 sec, that Attila the Hun is my 44th great grandfather.

Guest
Johnny says:
2 November 2015

I’m adopted and although I know my biological mother I am finding it difficult to get a truthful answer about who my father is. I was hoping a DNA test might help me in my search as one possibility was a man supposed to be from India.

Guest
diane sole says:
21 February 2017

I think it’s time Which looked into the various tests (not so much which type does what, this info is easily available) but which companies offering tests are well established (not be here today gone tomorrow) , have reputable provenance and how much