The DNA testing industry is booming today. But scientists are questioning the accuracy promised by DNA sampling used to trace generations of ancestors.
When Scottish actor Tom Conti discovered he was related to Napoleon, friends joked that they could see the similarities. Comedian Eddie Izzard was fascinated to learn recently of his Viking heritage, while the TV presenter and novelist Judy Finnigan was thrilled to be told she is descended from an ancient Tuscan princess.
To uncover the secrets of their ancestry, all three had relied on the same technique: DNA sampling. Once family history buffs were content to delve deep into their family tree — something the Internet has facilitated to astonishing effect, as public records and archives are put online. Now, however, genetic ancestry testing is all the rage. All it requires is for the subject to take a mouth swab, post it to a laboratory, where the DNA contained in the cells is examined and, hey presto, their ancestors are mapped.
The testing firms offer the prospect of discovering “deep ancestry”. Enthusiasts no longer have to restrict themselves to charting their great-grandfather’s roots or their Domesday lineage, but can find out to which continent their African ancestors emigrated many thousands of years ago.
It is not surprising, then, that this industry is booming. Tens of thousands of tests, which cost around £200, have been taken in Britain in the past few years, and they are even more popular in America. It is a growing segment of a much larger ancestry business, with the website ancestry.com recently valued at £1 billion.
Yet leading scientists challenged the basis of the tests recently. The Sense About Science campaign group claimed that the practice is as questionable as astrology.
The scientists do not dispute the methods of the test. A mouth swab is a routine way to extract an individual’s DNA in order to identify certain genetic “markers”. These portions of DNA will be compared to a database of samples to ascertain how common they are among populations on different continents. Sense About Science agrees that such testing can be useful to verify, for example, that two adults shared a common ancestor a few hundred years ago. But they are highly sceptical that the tests say much about our ancient lineage.
Take the company Oxford Ancestors, which charges £199 for its Matriline DNA Service offering customers “a premium quality ‘Seven Daughters of Eve’ certificate, signed by Professor Sykes (its chairman), identifying from which of the Seven Daughters you are descended”.
It is interpretations such as this that Sense About Science questions. “People often think of ancestry as being like a redwood forest of gigantic trees, well separated from each other, with their own trunk and their independent branches,” says Steve Jones, emeritus professor of genetics at University College, London. “In fact, it is more like a mangrove swamp — all the trees interlink above and below the ground and you can’t say where this tree starts and where that tree finishes.”
Some of the tests only examine Y chromosomes, which account for little of an individual’s overall DNA. They allow researchers to trace someone’s male line ancestry only. But this omits the maternal line entirely, as well as, for example, the father’s mother.
“You’ve only got one male line ancestor in each generation,” says Prof Mark Thomas, another supporter of Sense About Science. “As you go back in time, the proportion of your ancestry that this (single male) line represents becomes tiny quite quickly.” In other words, the male line accounts for one-16th of their great grandparents’ lineage.
The scientists also question the precision that some of these firms claim to offer. It is, they argue, impossible to confirm that you are descended from a Viking (rather than from an area of Northern Europe that may have been home to them), let alone a particular historical figure, such as Cleopatra.
“If they say, ‘We’ve tested your Y chromosome and you’ve got a match with a bunch of people in Norway’, there is a chance you got that from some Viking movement,” says Prof Thomas. “But we don’t know what that chance is. It may be that the Y chromosome actually originated in Britain but just happened to increase in frequency in Norway. The companies invariably explain it with the sexiest story — you are a Viking, so go and buy your helmet.”
Some in the industry agree that the scientists have a point. David Nicholson, who runs the testing firm DNA Worldwide, says there are “subtleties” in how test results are written up. “If we say your ancestry comes from Northern Europe and there are common ancestors there to where the Vikings came from, we are not telling people their ancestry is Viking,” he insists. “But in some other (companies’) reports, they go so far as to say, ‘You’ve got Viking ancestry, you were in this part of the world and your ancestors were farming with arable tools on the land.’ That would be a jump.”
Prof Jones believes that ultimately the tests are pointless, even with rigorous scientific analysis, because we all share the same common ancestor. “If I get a white European to shake hands with the person next to them, there is about a 30 per cent probability that they are talking to their seventh or eighth cousin,” he says. “The common ancestor of everyone alive today lived something like 3,500 years ago. So you are not saying anything when you have your test done and find out you are descended from Romans. Everybody is.”
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