Mark Thomas, Professor of Evolutionary Genetics in the Research Department of Genetics, Evolution and Environment at University College London, doesn’t think much of the announcement that a million British men are descended from the Romans. The following is an excerpt from a rather lengthy article by Thomas, posted at The Guardian website.

You may have missed the latest genetic discovery. As reported by The Daily Telegraph on Friday: “One million British men may be directly descended from the Roman legions”. The story reappeared on Sunday, at the Who Do You Think You Are – Live event at London’s Olympia, when it was repeated by Alistair Moffatt, the managing director of BritainsDNA, the company behind the claims.

Such stories are becoming increasingly common in newspapers, on television and radio. Last week on the BBC miniseries Meet the Izzards we were told that Eddie Izzard is a Viking descendant on his mother’s side and an Anglo-Saxon descendant on his father’s. Last year the Observer reported that Tom Conti has Saracen origins and is a relative of Napoleon Bonaparte.

And for upwards of £150 you too can have your DNA “tested” by any of a number of direct-to-consumer ancestry companies. But how reliable are these claims? The truth is that there is usually little scientific substance to most of them and they are better thought of as genetic astrology.

For some time it has been possible to compare DNA sections among individuals; and in a broad sense greater genetic similarity means greater relatedness. But you have inherited different sections of your DNA from different ancestors, and as we look back through time the number of ancestors you have almost doubles with each generation (it would double exactly were it not for the fact that we are all somewhat inbred).

Read the full article.