By testing the Y-DNA and mtDNA of living people we can learn about the present-day distribution of the different haplogroups, but it is much more difficult to make inferences about the past from modern DNA. Our ancestry is convoluted and very complicated, and is confounded by migration, genetic drift and population size changes in the past. Throughout human history migration has been the rule rather than the exception, and we now know from empirical data that "the current inhabitants of a region are often poor representatives of the populations that lived there in the distant past" (Pickrell and Reich 2014). There is also considerable uncertainty in the dating of the different branches of the Y-DNA and mtDNA trees. Nevertheless, despite these limitations there are some researchers who still try to link Y-DNA and mtDNA haplogroups with specific tribes and historical events. It is, of course, very easy to make such associations and – given the flexibility of interpretative phylogeography – to make the data fit your favourite hypothesis, but there are almost always many different explanations that would fit the available data (Nielsen and Beaumont 2009).
In addition, Y-DNA and mtDNA represent an increasingly smaller percentage of our ancestry as we go further back in time, and consequently they are only weakly informative about our deep ancestry. Y-DNA and mtDNA are also more prone to the problems of genetic drift. However, despite the limitations for deep ancestry, Y-DNA and mtDNA tests are very useful for genealogical purposes where the results can be analysed in combination with genealogical and historical documents.
Ancient DNA is now beginning to transform our knowledge of the past. Although only a limited number of Y-DNA and mtDNA samples are available it is already very clear that the distribution and frequency of Y-DNA and mtDNA haplogroups were very different in the past. With the new next generation sequencing methodologies it is possible to sequence the entire genome whereas early ancient DNA studies focused mainly on mitochondrial DNA.
Real science
The DNA Cymru programme did feature some real science. There were interviews with Professor Sir Walter Bodmer and Professor Peter Donnelly from the
People of the British Isles Project (POBI). This project is based at the University of Oxford. They published a landmark paper on the genetic composition of the British Isles earlier this year (Leslie et al 2015). The POBI paper was based on analysis of autosomal DNA, but Y-DNA and mtDNA have also been extracted, and Professor Mark Jobling at the University of Leicester is in the process of analysing these results. This should provide a useful insight into the geographical distributions of the Y-DNA and mtDNA haplogroups of the British Isles. It is strange that the programme makers do not seem to have been aware of this Y-DNA and mtDNA research prior to arranging their partnership with a commercial company to do the same type of testing.
Professor Dan Bradley of Trinity College Dublin was interviewed about his ancient DNA research. He is sequencing 30 DNA samples "across the whole pre-history of Ireland". He says "It's almost like dropping a plumb line through history". He cautioned about making inferences from modern DNA: "There's one problem about looking at the present to study the past, and that is, essentially, the past is a different country. The models we bring up from the present to understand the past may miss big things". He cited the example of Ötzi the Iceman who was found in the Alps but who has a genetic signature which is more like the people of the southern Mediterranean.
The programme also featured interviews with other academics. Archaeologist Rhys Mwyn described Brymbo Man, a Bronze Age skeleton whose burial was typical of the Beaker People. Brymbo Man's DNA has not yet been tested but it would be an interesting study. The linguist and historian John Koch discussed the migration of the Beaker People.
It is not clear how much the academics who agreed to appear on the programme knew about the nature of the collaboration with CymruDNAWales/ScotlandsDNA. The S4C website does state: It’s important to remember that - except where they comment specifically on screen in the programmes – their involvement should not be read as an endorsement of commercial DNA testing". I noticed earlier this week that the text had been changed to clarify that "their involvement should not be read as an endorsement of commercial DNA testing
or inferences made from such data", no doubt after concerns were raised by some of the credible scientists interviewed.
Celebrity DNA
The credible science was interspersed with stories about three Welsh celebrities
– Caryl Parry Jones, Roy Noble and Ken Owens
– who received their DNA results from CymruDNAWales on the programme. Roy Noble was told that his G2a haplogroup was found in the first people who brought farming to Europe. Ken Owens was told that his R1b sub-haplogroup S145 (L21) was brought to Wales with the Beaker People. However, we do not have any way of knowing when these haplogroups appeared in Wales and this is pure speculation. By mixing up the company's storytelling with legitimate scientific research from respected scientists like Dan Bradley and Peter Donnelly, the company are no doubt hoping that some of that credibility rubs off on their own "findings". Unfortunately viewers who are not familiar with the scientific literature might not realise where the legitimate science ends and the storytelling begins.
Commercial interests
The minimum standard for scientific credibility is publication in a peer-reviewed scientific journal. Unfortunately none of the "research" from the CymruDNAWales project has been published anywhere. It is in any case unlikely to get through the peer review process in a respected journal. In order to participate in the DNA Cymru "project" it is necessary to order an expensive DNA test from CymruDNAWales. Consequently the samples are likely to be very biased.
It was reported in the programme on Sunday that DNA Cymru had conducted tests on 1000 people. It seems highly likely that many of these people were encouraged to pay for a test after seeing the launch programme. I note too that the tests are still being surreptitiously promoted on the S4C website. Visitors are invited to click on a link to find out more about the CymruDNAWales "project" but the link provides no information about a scientific research project; instead it takes you to the Moffat Partnership's CymruDNAWales website where you can buy one of their ancestry tests.
We learnt from the programme that the principal scientist for the DNA Cymru series is Dr Jim Wilson. It just so happens that he is also the
Chief Scientific Officer of CymruDNAWales and the other associated companies. He is a
director of the Moffat Partnership and is a major shareholder with the company. His company, and in particular his business partner Alistair Moffat, have been heavily criticised for manipulating the press and misleading the public with their outrageous stories. At UCL
we set up a whole website to counter these unscientific claims, an initiative which has been very well received by the academic community. One is therefore left wondering if the choice to partner with this company was made not as an independent editorial decision but as a result of the friendship of S4C's CEO Ian Jones with Alistair Moffat.
I should clarify that the Chromo 2 test sold by ScotlandsDNA is a perfectly valid test if you are interested in learning about your Y-chromosome and mitochondrial DNA markers. It is only the haplogroup reports provided by the company that have no scientific validity. There is nothing wrong with a TV company using the services of a commercial company. However, S4C, as a public service broadcaster, is bound by
strict editorial guidelines to ensure that its impartiality and integrity are not compromised. It has a duty to provide accurate content which is not influenced by commercial interests.
Although the programme was better than the previous one, this is mainly because they incorporated highly respected scientists like Dan Bradley and Peter Donnelly. It is still a big disappointment to see a public service broadcaster being used to promote a commercial genetic ancestry company in the guise of a research project, and to see speculative stories mixed up in such a misleading way with serious science.
Further reading
For more information on the problems of making inferences about deep ancestry from Y-DNA and mitochondrial DNA see the pamphlet
Sense About Genetic Ancestry Testing from Sense About Science. This guide was written by my colleagues at UCL Professor Mark Thomas and Professor David Balding in collaboration with some of the big names in population genetics: Dr Turi King, Dr Lounès Chikhi, Dr Rosalind Harding, Professor Mark Jobling and Professor Guido Barbujani.
For further information on phylogeography and the problems with the interpretative approach see the
ISOGG Wiki article on phylogeography.
References
Balloux F (2009).
The worm in the fruit of the mitochondrial DNA tree.
Heredity 104: 419-420.
Chikhi L (2010).
Update to Chikhi et al.'s "Clinal Variation in the Nuclear DNA of Europeans” (1998): Genetic Data and Storytelling - From Archaeogenetics to Astrologenetics?" Human Biology 81(5/6): 639-643.
Goldstein DB, Chikhi L (2002).
Human migrations and population structure: what we know and why it matters.
Annual Review of Genomics and Human Genetics 3: 129-152.
Pickrell J, Reich D (2014).
Towards a new history and geography of human genes informed by ancient DNA.
Trends in Genetics 2014; 30 (9): 377-389 (subscription required). Available as a
preprint from from BioRxiv.
