My letter in Family Tree Magazine about "genetic homeland" stories

The August 2014 issue of Family Tree Magazine includes a letter I wrote in response to two stories in their July issue which claimed that it is possible to identify someone's "genetic homeland" from a DNA test. There was not space in the magazine to include the full text of my letter and the editor has kindly given me permission to reproduce the full letter here.

In your July issue you published two articles which claimed to show that it is possible to pinpoint your "genetic homeland" a thousand or more years ago by taking a simple DNA test. It would indeed be wonderful if a DNA test could give us this information but sadly it is not possible. 

The first story “DNA: find your ancestral home” (p9) referred to a new autosomal DNA test developed by a company called Prosapia Genetics. They claim that they are able to pinpoint someone’s genetic homeland one thousand years ago and that their test is “accurate to home village with a time resolution of the past 1,000 years”. The underlying research on which this test is based was published in a scientific journal (Elhaik et el 2014, Nature Communications 5: 3513). However, the researchers were only able to place 50% of people within 450 kilometres of their country of origin, which is hardly the level of precision claimed. Furthermore the research focused solely on the present-day country of origin and made no attempt to determine an ancestral origin one thousand years ago. Such a method is best thought of as human provenancing – finding the location where an individual’s genotype is most likely to be found – not a method for inferring ancestry. Indeed, if you go back one thousand years you have in theory about 35 billion ancestors, although you actually inherited DNA from only a small, random subset of those ancestors. Identifying a single location as the “genetic homeland” of either all your pedigree ancestors or just the DNA ancestors would be a meaningless exercise. The International Society of Genetic Genealogy received a number of reports from dissatisfied customers of Prosapia Genetics, many of whom had received bizarre results placing their "genetic homeland" in the middle of a river or ocean. Fortunately they were able to get refunds from PayPal. 

Dr Tyrone Bowes, the author of the second article "Routes to roots" (pp14-18), claims to be able to tell his customers when their ancestors arrived in Britain and where they came from based on recurring surname matches received as part of a commercial Y-chromosome DNA test. DNA testing is a very useful tool for the genealogist, and Y-DNA matches can often provide clues about our recent origins. However, Y-DNA results should always be interpreted in combination with genealogical and historical records. While a Y-DNA test is very good at indicating whether or not two people share a recent male-line ancestor, it is much more difficult to determine precisely when or where that ancestor might have lived. For example, a match on 34 out of 37 markers could indicate a shared ancestor who lived 200 years ago or 2000 years ago, and there is no way of determining the precise timeframe. Furthermore, surnames did not become common in Britain one thousand years ago, as is claimed. They were introduced into Britain with the Norman Conquest but the adoption of surnames was a gradual process. While most English people had acquired surnames by the fifteenth century, surnames were not adopted until the nineteenth century in some parts of Wales. In the Highlands of Scotland the clan system survived until the eighteenth century, and people adopted the name of the clan rather than using an hereditary surname. Even when surnames are passed on through the fatherline the link between the Y-chromosome and the surname is often broken as a result of illegitimacy, cuckoldry, adoption or name changes. In addition, there is an inherent American bias in the commercial databases. Consequently Y-DNA matches will often tell us more about non-paternity events in Colonial America in the last 400 years, rather than a person’s origins in the British Isles. All these factors need to be taken into account when interpreting DNA results. 

The mutations that determine haplogroups (the deep-rooted branches of the human Y-DNA tree) did indeed occur at a specific time and place several thousand years ago, but determining when and where that happened is a different matter entirely. We are reliant on making inferences from the DNA of living people. However, the current distribution of haplogroups differs from each of the distributions at different times in the past. The changes occur due to migration and the randomness of genetic drift. As more ancient DNA samples become available it might one day be possible to provide some answers, but we are not there yet and it is unlikely that we will ever be able to "precisely reconstruct our ancestral journey". 

Readers wishing to understand more about the legitimate uses of DNA testing for genealogy and the limited inferences that can be made from deep ancestry tests might like to refer to the new “Debunking genetic astrology” website that I have worked on with my colleagues at University College London: www.ucl.ac.uk/mace-lab/debunking. In particular readers might like to look at the page on dubious commercial claims (www.ucl.ac.uk/mace-lab/debunking/companies) where the genetic homeland stories are discussed in greater detail.

The editor also included in the August issue of Family Tree Magazine responses to my letter from Vladimir Makarov of Prosapia Genetics and Tyrone Bowes, the creator of the Irish, Scottish and English Origenes websites. Unfortunately, neither letter addressed any of the issues I'd raised. Vladimir Makarov argued that his reports do reflect ancient origins simply because the reference populations he uses are "totally agnostic of political boundaries". He failed to recognise that these reference populations are themselves possibly admixed and do not necessarily represent the population in the same location one thousand years ago. Tyrone Bowes went into great detail about a case report that he'd compiled for a Mr Valentine which purported to show a link with the McGregors. It seems that his entire dating method has been based on this single case. Numerous scientific studies have of course demonstrated that mutations occur at random, and any attempt to investigate the validity of matches must take into account the uncertainties in the TMRCA (time to the most recent common ancestor) calculations. My points about differing times of surname adoption and non-paternity events remained unanswered.

For further information about Prosapia Genetics and the case reports offered by the Irish, Scottish and English Origenes websites see my two earlier blog posts:

- Driving in the wrong direction with a dodgy DNA satnav (a critique of the test from Prosapia Genetics)
- A look at the genetic homeland case reports from English Origenes, Irish Origenes and Scottish Origenes

© 2014 Debbie Kennett

Understanding genetic ancestry testing and debunking genetic astrology

I'm pleased to announce the launch of a new UCL website devoted to the subject of genetic ancestry testing. I've been working on this website with my UCL colleagues Professor David Balding, Professor Mark Thomas and Adrian Timpson.

The aim of the website is to explain how genetic ancestry tests work and to explain what such tests can and can't tell you, but with a particular focus on the inferences made about our deep ancestry. I am a passionate advocate for the use of DNA testing for genealogical purposes. DNA can be a very powerful tool when used in combination with both genealogical and historical records, especially now that the genetic genealogy databases are so large. However, it is much more difficult to make inferences about deep ancestry based on DNA evidence alone. Unfortunately many misleading stories and dubious claims which are not supported by the scientific evidence have appeared in the media. Such "genetic astrology" stories only serve to undermine public confidence in DNA testing and prevent the subject from being taken seriously. It is often difficult for the uninformed reader to make sense of these stories and to separate the facts from the storytelling. We hope that our website will go some way to setting the record straight.

The new website is an extension of our previous website which was devoted to the BritainsDNA saga. BritainsDNA are not by any means the only source of exaggerated claims appearing in the media, though to our knowledge they are the only company who have resorted to legal threats in an attempt to silence their critics. The BritainsDNA saga still features prominently but we have now added additional sections to the website looking at dubious claims from other commercial organisations, and deconstructing some of the doubtful research claims that have appeared on TV or in the press. We also have a section devoted to some of the more problematic theories about our genetic ancestry that are circulated over the internet, in the press, and across social media platforms. The new website can be found here:

https://www.ucl.ac.uk/mace-lab/debunking

The website is inevitably a work in progress, and will evolve over time. We would welcome any feedback and in particular suggestions for further topics which should be covered.